JAVA CODE SPOT

JAVA Programming : String Class

2012-04-04T10:13:00.003-07:00

JAVA String

In Java there is eight primitive data type and also a special String class in java.lang.string package for string handling.
String are like sequence of characters. String is not a primitive data type (because strings are objects) but the java language provides some special support to strings so, sometimes its seems like Strings are one of the primitive type.
String are very widely used in java and if you ever done some programming in Java than you must have created a string in some way or the other.
For example the most direct way to create an String object is by just enclosing some characters in double quotes("").

     String str ="This is a String";

String is an object in java so it can also be declared as any other object is declared using new keyword.

      String str = new String();

String class has several constructors to create a String object. The above example is one of the way simplest way to create an string. The constructor used in the example is a no argument constructor or we can say a default constructor which will create a empty String i.e. str will be an instance of String with no character in it.
Below is an example which show a number of ways to create a String object.

public class StringExample {

   public static void main(String[] args) {

    // this is will create an empty String

    String str = new String();



    // Creating a String using an character array

    char ch[] = { 'J', 'a', 'v', 'a', 'C', 'o', 'd', 'e', 'S', 'p', 'o', 't' };

    String strChar = new String(ch);



    // Creating a String from character array's subarray

    //in arguments give the source character array, 

    //starting point and number of character after that

    String strSubChar = new String(ch, 4, 4);

    //Creating an array using byte array of ASCII Value

    byte b[] ={74,65,86,65};

    String strByte = new String(b);



     //Just like character array we can also create 

    //string form subarray of byte array

    String strByteSub = new String(b,2,2);



     System.out.println(str);

    System.out.println(strChar);

    System.out.println(strSubChar);

    System.out.println(strByte);

    System.out.println(strByteSub);

   }

}

Output of Program:

There are some more String Constructors but we will discusses them in later tutorials.

Methods of String Class:- String class provides several methods for string manipulation and these are going to be very useful in many situation like Input validation, text analysis and file conversions etc. In this tutorial we are going to discuses most of the common methods of String class.

public charAt(int index) :-
public int length() :-
public String concat(String s) :-
public boolean equals(String s)
public boolean equalsIgnoreCase(String s)
public String substring(int begin)
public String substring(int begin,int end)
public String toLowerCase()
public String toUpperCase()
public String trim()
public int indexOf(int ch)
public int indexOf(int ch, int startIndex)
public int indexOf(String str)
public int indexOf(String str, int startIndex)

JAVA Programming : Factorial

2012-01-29T02:34:00.000-08:00

JAVA Factorial

Factorial is a mathematical operation Factorial of a positive number n is denoted by n! and defined as the product of all numbers from 1 to the n. The syntax of factorial of number n is:

n! = n*(n-1)*(n-2)*(n-3)......2*1

For Example:-

7! = 7 × 6 × 5 × 4 × 3 × 2 × 1 = 5040

Note:- Factorial of zero is 1 (i.e. 0! = 1).

import java.util.Scanner;

 public class Factorial {

  public int fact(int n){

    int fact =1;

    for (int i =1 ; i <= n; i++) {

      fact=fact*i;

    }

    return fact;

  }



   public static void main(String[] args) {

    Factorial f = new Factorial();

    System.out.println("Enter a Nu4mber");

    Scanner scan = new Scanner(System.in);

    int num = scan.nextInt();

    int result = f.fact(num);

    System.out.println("Facotial of "+num+" is "+result);

  }

}

Output of Program:-

JAVA Programming : Pyramids 2

2012-01-27T09:05:00.000-08:00

JAVA Pyramids 2

In the previous post we have discussed about different pyramids examples and we will continue to do some more examples. In this tutorial I will post the code of some more complex pyramid examples.

         *

        ***

       *****

      *******

     *********

Code for this program:-

import java.util.Scanner;

  public class Pyramid {  

  public static void main(String[] args) {

    System.out.println("Enter the length of pyramid");  

    Scanner scan = new Scanner(System.in);

    int rows = scan.nextInt();

    System.out.println("-------Output------");

    for (int i = 1; i <= rows; i++) {

      for (int j = rows-1; j >= i; j--) {

        System.out.print(" ");

      }

      for (int k = 1; k <= i; k++) {

        System.out.print("*");

      }

      for (int l = 2; l <= i; l++) {

        System.out.print("*");

      }

      System.out.println();

    }

    System.out.println("-------------------");

  }

}

Output of Program:-

      ************     

      *****  *****

      ****    ****

      ***      ***

      **        **

      *          *

Code for this Program:-

import java.util.Scanner;

 public class Pyramid {  

  public static void main(String[] args) {

    System.out.println("Enter the length of pyramid");  

    Scanner scan = new Scanner(System.in);

    int rows = scan.nextInt();

    System.out.println("-------Output------");

    for (int i = 1; i <= rows; i++) {

      for (int j = rows; j >= i; j--) {

        System.out.print("*");

      }

      for (int k = 2; k <= i; k++) {

        System.out.print("  ");

      }

      for (int l = rows; l >= i; l--) {

        System.out.print("*");

      }

      System.out.println();

    }

    System.out.println("-------------------");

  }

}

Output of Program:-

      ************     

     *****  *****

     ****    ****

     ***      ***

     **        **

     *          *

     *          *

     **        **

     ***      ***

     ****    ****

     *****  *****

     ************

Code for this Program:-

JAVA Programming : Pyramids

2012-01-26T06:40:00.000-08:00

JAVA Pyramids

In the last few tutorials we have discussed some basic concepts of programming and in next few posts we will be using them to make some simple programs.

Pyramids are very common examples that I think every programmer had made at the time of start learning programming. Pyramids are very useful in teaching the use of loops. There are numerous types of pyramids example. Lets start with an basic example.

*
**
***
****
*****

Creating the Pyramid Program:- We will make an simple program that will take an integer input from user and print the asterisks pyramid with that much number of rows.

import java.util.Scanner;

public class Pyramid {  

  public static void main(String[] args) {

    System.out.println("Enter the length of pyramid"); 

    Scanner scan = new Scanner(System.in);

    int rows = scan.nextInt();

    System.out.println("-------Output------");

    for (int i = 1; i <= rows; i++) {

      for (int j = 1; j <= i; j++) {

        System.out.print("*");

      }

      System.out.println();

    }

    System.out.println("-------------------");

  }

}

In this program, first we take an integer input form user using Scanner class and than nested for loop is declared (i.e. a loop inside another loop). In this the outer for loop will run the same number of times as enter by user(from 1 to the enter number) and after every iteration it will print a new row and increment the loop control variable by 1. Inside the outer loop a new inner for loop is declared which will print the same number of asterisk as the current iteration value of outer loop control variable.

Output of Program:-

Reverse Pyramid: The next program we will be making is to print a reverse pyramid. The reverse pyramid will look like:-

*****
****
***
**
*

The code for printing a reverse pyramid is not very different from the previous one. Infact we can actually do it just by changing one line. Take a look at the code below.

import java.util.Scanner;

  public class Pyramid {  

  public static void main(String[] args) {

    System.out.println("Enter the length of pyramid");  

    Scanner scan = new Scanner(System.in);

    int rows = scan.nextInt();

    System.out.println("-------Output------");

    for (int i = rows; i >= 1; i--) {

      for (int j = 1; j <= i; j++) {

        System.out.print("*");

      }

      System.out.println();

    }

    System.out.println("-------------------");

  }

}

If you look at the code above, we have just made a slight change in the declaration of outer loop. This it the outer loop will start from the entered number and end at 1. After every iteration we decrease the value by one.

Output of Program:-

Some more examples of different Pyramids:-

*
**
***

****

*****

If you look at this example, it can look a bit confusing, but it is not as much difficult as you might think. Lets take a look below.

----*
---**

      --***

      -****

      *****

Now its easy to understand the logic for this program. For this program we have to need to an extra for loop in our previous code of pyramid. Here is the code :

import java.util.Scanner;

 public class Pyramid {  

  public static void main(String[] args) {

    System.out.println("Enter the length of pyramid");  

    Scanner scan = new Scanner(System.in);

    int rows = scan.nextInt();

    System.out.println("-------Output------");

    for (int i = 1; i <= rows; i++) {

      for (int j = rows-1; j >= i; j--) {

        System.out.print(" ");

      }

      for (int k = 1; k <= i; k++) {

        System.out.print("*");

      }

      System.out.println();

    }

    System.out.println("-------------------");

  }

}

Output of Program:-

For more pyramid examples go to : JAVA Pyramids 2

JAVA Programming : Break, Continue And Return

2012-01-22T03:24:00.000-08:00

JAVA Break, Continue And Return

Java has three type of branching control keywords: break, continue and return. These keywords are used to change the normal flow of execution of program.

Break keyword :

The break keyword is used to stop the execution of the loops. In many situations we need to get out of the loop before the loop execution is complete. Whenever a break keyword is encountered inside a loop the execution gets out of loop and start executing the next line of code after the loop. The break statement is of two types: labeled and unlabeled.

Unlabeled break statement:

Unlabeled break statement is used to get out of a single loop. If unlabeled break is used inside the nested loops it will exit only from the loop in which break is used. Lets see the example below:

public class UnlabeledBreak {

   public static void main(String[] args) {

    int i = 1;

    while (i < 10) {

      if (i == 5) {

        break;

      }

      System.out.println("i = " + i);

      i++;

    }

  }

}

Output of Program:

Labeled Break Statement:

Labeled breaks statement is used when we need to break the nested loops. Lets understand the difference between Labeled and Unlabeled break statement with an example.
In this example we need to traverse a 2D array and print the elements of array until a particular element is found. To do this we have to use nested loops. Now to break and get out of the nested loops we need to use labeled break.

public class LabeledBreak {

   public static void main(String[] args) {

    int[][] a = {{1,2,3},{4,5,6},{7,8,9}};

    OuterLoop:

    for (int i = 0; i < a.length; i++) {

      for (int j = 0; j < a[0].length; j++) {

        System.out.println(a[i][j]);

        if(a[i][j]==6){

          break OuterLoop;

        }

       }

    }

     System.out.println("Program Ends");

   }

}

Output of Program:-

Continue Keyword:- Continue statement statement is used to skip a single iteration of a loop. Whenever a continue keyword is encountered inside a loop, the current iteration of loop ends just like a normal end of any iteration without executing the statement written after the continue statement inside the loop. Just like break statement continue statement is also of two types: labeled and unlabeled.

Unlabeled Continue Statement:

public class UnlabeledContinue {

   public static void main(String[] args) {

    int[] a = {1,2,3,4,5,6,7,8,9,10,11,12,13,14,15};

    System.out.println("Numbers divisible by 3 or 5");  

    for (int i = 0; i < a.length; i++) {

      if(a[i]%3!=0 && a[i]%5!=0){

        continue;

      }

      System.out.println(a[i]);

    }

  }

}

Output of Program:

Labeled Continue Statement:

public class ContinueLabel {

   public static void main(String args[]) {

    outer:

    for (int i = 1; i < 10; i++) {

      for (int j = 1; j < 10; j++) {

        if (j > i) {

          System.out.println();

          continue outer;

        }

        System.out.print((i)+" ");

      }

    }

    System.out.println();

  }

}

Output of Program:-

Return Keyword:- Return statement is a bit different form break and continue as break and continue changes the normal control flow of loops but return statement works on the control flow of the method. Return statement stops execution of the method and transfer the control back to the caller of the method. The return statement can be used in two ways, return statement that returns a value and another that does not return a value. Return statement must return the same type of value as defined in the declaration of method. If the method is defined as void than return statement will not return any value.

public class ReturnStatement {



  public static void main(String[] args) {

    ReturnStatement rs = new ReturnStatement();

    System.out.println("Largest Number is: " + rs.largestNumber(5, 10, 15));

   }



  public int largestNumber(int num1, int num2, int num3) {

    int largest = 0;

    if ((num1 > num2) && (num1 > num3)){

      largest = num1;

    }

    else if ((num2 > num3) && (num2 > num1)){

      largest = num2;

    }

    else{

      largest = num3;

    }

    return largest;

  }

}

The use of return statement will be more clear in upcoming tutorials and we will be using it more and more now.

JAVA Programming : For Each Loop

2012-01-10T11:12:00.000-08:00

JAVA For Each Loop

For each loop or Enhance For loop is a extended version of basic for loop which was introduced in Java 5. For each loop is designed to make iteration over arrays and collections much easier. For each loop also makes the code more readable. In this post we will learn about basics of For each loop using Arrays. We will discuses more about For Each loop when we learn about Collections and Iterator.

Syntax of For Each Loop:-

for (type var : arr) {

         //body-of-loop  

    }

Example of For Each Loop:- This is a very simple example in which we will traverse an array using For Each loop and print all the elements of the array.

 public class ForLoop {

  public static void main(String[] args) {

    char[] charArr = {'a','b','c','d','e'};    

    for (char c : charArr) {

      System.out.println(c);

    }

  }

}

To understand the difference between Basic For loop and For Each Loop, here is the same program using For Loop.

 public class ForLoop {

  public static void main(String[] args) {

    char[] charArr = {'a','b','c','d','e'};    

    for (int i = 0; i < charArr.length; i++) {

      System.out.println(charArr[i]);

    }

  }

}

Advantages of For Each Loop:-

Less number of variables are used
Less chance of errors
Improve Readability

Limitation of For Each Loop:-

Cannot traverse multiple collection at once.
Iterates only forward by single steps.

JAVA Programming : For Loop

2011-12-25T09:16:00.000-08:00

JAVA For Loop

For loop in java is one of the most common type of loop. There are two types of for loop:

Basic For loop
For Each loop (Introduced in Java 5)

Basic For loop:

For loop declaration has there parts : initialization, termination condition, iteration expression. These parts are separated by semicolons.

Syntax of for loop:-

    for(initialization; condition; iteration){ 

      //set of statements

   }

Initialization part: The initialization part of for loop is executed only for the first when the loop begins. It lets you declare and initialize one or more variables of the same types. One thing to note when the declaring a variable in for loop is the scope of variable. If the variable is declared in the for loop the variable's scope is limited to the for loop.

Condition part: The condition part must be an Boolean expression. In condition part there cannot be multiple test condition but we can use logical operators to make a logical expression that evaluates into a Boolean result. The body of the for loop is executed only if the condition is true else the loop is terminated.

Iteration part: After every iteration of for loop's body, the iteration part is executed. This is the part where you can set the change in loop control variable. The given example will give a better understanding of working of for loop.

Example of for loop:- This is a very simple example of for loop which will take an integer input form user and print the table of that number.

import java.util.Scanner;

 public class ForLoop {

  public static void main(String[] args) {

    System.out.println("Enter a number");

    Scanner scan = new Scanner(System.in);

    int userInput= scan.nextInt();

    int result=0;

    System.out.println("Table of "+userInput);

    System.out.println("--------------");

    for (int num = 1; num <= 10; num++) {

      result=userInput*num;

      System.out.println(userInput+" * "+num+" = "+result);

    }

  }

}

In this program, a Scanner class is used to take input from user. Next, is a for loop which is declare to run10 times. This for loop starts with initialization int num=1, and executes the body part till the condition num<=10 becomes false, after executing the body of for loop for each and every time num value will be incremented by 1.

Output of Program:-

Different ways of using For Loop:- For Loop can be used in different ways and sometimes it can be very complex. We will discuses this in the examples below. In For loop there is one thing to notice that all three declaration part of for loop can be left blank.

     for ( ; ; ) {   

       //infinite loop

    }

The code above is will work as an infinite loop or endless loop and it will work same as while(true) loop.

As we now know that all three part of For loop are optional and can be left blank but it is very interesting to know that what kind of code you can write in these parts. The condition part is the only part of for loop declaration for which there is a rule defined that it must be an Boolean expression. In the remaining two, Initialization and Iteration part we can actually write any peace of code.

 public class ForLoop {

  public static void main(String[] args) {

    int i = 0;

    for (System.out.println("Initializtion Part"); i<5 ;

     System.out.println("Iteration Part") ) {

       System.out.println("Body part");

       i++;

    }

  }

}

Output of Program:-

Use of comma and logical operators in For loop:- In For loop we can use multiple statements in initialization and iteration parts using comma. In initialization part we can define multiple variables by separating the variables with comma but the variables must be of same type.
As we know, condition part of the for loop must be an boolean expression therefor use of comma is not allowed but we can use logical operators to make a valid boolean expression.

 public class ForLoop {

  public static void main(String[] args) {

     for (int a=1, b=5, c=10; a<b || a<c ; a++,b--,c--) {

      System.out.println("a = "+a+" b = "+b+" c = "+c);

    }

  }

}

Output of the program:-

In the next post we will learn about For each loop or Enhanced For Loop.

JAVA Programming : Do While Loop

2011-11-23T10:56:00.000-08:00

JAVA Do While Loop

Do Loop is very similar to the while loop. The only difference between while and do while loop is that the while loop first checks the condition and executes the body of while loop only if the conditions results as true but in while loop the condition is evaluated after the loops body is executed once, so even if the condition is false at the first time the body of loop will be executed at least once.

   do{

     //set of statement

  } while(condition);

Example of Do While loop:- The examples below will explain the working of do while loop.

In the examples below the while loop and do while will work exactly same i.e. will give the same output.

public class DoWhileLoop {

   public static void main(String[] args) {

  int i=1;

    do {

      System.out.println("enter into loop");

      i++;

    } while (i<=10);

  }

}

public class DoWhileLoop {

   public static void main(String[] args) {

    int i = 1;

    while (i <= 10) {

      System.out.println("enter into loop");

      i++;

    }

  }

}

In the examples below the while loop and do while will not give the same output.

public class DoWhileLoop {

  public static void main(String[] args) {

  int i=11;

    do {

      System.out.println("enter into loop");

      i++;

    } while (i<=10);

  }

}

public class DoWhileLoop {

  public static void main(String[] args) {

    int i = 11;

    while (i <= 10) {

      System.out.println("enter into loop");

      i++;

    }

  }

}

In these examples the condition will be false at the first time so the body of while loop will never get processed but the body of do while will be processed once.

JAVA Programming : While Loop

2011-11-23T07:19:00.000-08:00

JAVA While Loop

Loops in java are the control flow statements that are used to repeat a block of code multiple times according to a given condition. There are three types of loops: For , Do , While. The while loop is very simple but very effective when we have to execute a block of code until a particular expression(condition) is true. The condition will evaluate into a boolean result.

Syntax of while loop:-

while(condition){
//set of statements
}

Example of while loop:- To understand the functionality of while loop lets see the example. While loop first checks the given condition, if the condition results into true then the statement written inside the while loop block will be executed and then the condition is checked again. This process goes until the given condition is false.

import java.util.Scanner;

  public class While {

  public static void main(String[] args) {

    int i=1;

    System.out.println("Enter any number to print table");

    Scanner scan = new Scanner(System.in);

    int num = scan.nextInt();



    while (i<=10) {

      System.out.println(num+" * "+i+" = "+num*i);

      i++;

    }  

  }

}

Output of Program:-

JAVA Programming : Switch Statement

2011-07-19T13:35:00.000-07:00

JAVA Switch Statement

Switch Statement is also a control flow statement like If statement. But Switch statement is a bit different from If statement, because an If statement can only choose one course of action form multiple choices but switch statement can have multiple outcomes. We will explain it below. A switch statement works only for convertible int values (like byte, int, short, char) and enum constants.

Syntax of Switch Statement:

  switch(expression){

      case constantOne:

        //set of statement   

      case constantTwo:

        //set of statement

      case constantThree:

        //set of statement

      default:

        //set of statement

 }

Now lets see the functionality of Switch statement: In a switch statement the flow of execution starts from top to down i.e. the first case will be evaluated and the second case and so on and wherever it finds the matching case it will execute the associated code block and the remaining code block till the end of switch. Let’s understand with an example:

public class SwitchStatement {

  public static void main(String args[]){   

    int a=2;

    switch (a){

    case 1:

      System.out.println("one");

    case 2:

      System.out.println("two");

    case 3:

      System.out.println("three");

     case 4:

      System.out.println("four");

     }  

  }

}

The output of this program is :

two

three

four

Here we can see that after finding the matching case, the associated code block and all the code blocks after that will get executed till the end of switch statement. This kind of situation is called fall through. To overcome this problem we can use break statement.

Break: Whenever the program finds a break statement, the execution of program jumps out of switch. Break statement is also used in loops like for and while. We discusses about it later.

 public class SwitchStatement {

  public static void main(String args[]){   

    int a=2;

    switch (a){

    case 1:

      System.out.println("one");

      break;

    case 2:

      System.out.println("two");

      break;

    case 3:

      System.out.println("three");

      break;

     case 4:

      System.out.println("four");

      break;

     }  

  }

}

This is same example as above but with a slight change. We have used the break statement in all cases. So, the output of this program will be:

two

This is because when it executes the case 2 block it will encounters a break statement and the execution of program will move out of switch immediately without executing remaining cases. This way it avoids the fall through situation.

Default: Default works same as Else in If-Else statement. In switch statement if there is no matching case the default case will get executed. Here is an example:

 import java.util.*;

public class SwitchStatement {

  public static void main(String args[]){

    int option=0;

    String week="";

    Scanner scn = new Scanner(System.in);

 

    System.out.println("Enter a Weekday"); 

    option=scn.nextInt();

    

    switch (option){

    case 1:

      System.out.println("Sunday");

      break;

    case 2:

      System.out.println("Monday");

      break;  

    case 3:

      System.out.println("Tuesday");

      break;

    case 4:

      System.out.println("Wednesday");

      break;

    case 5:

      System.out.println("Thursday");

      break;

    case 6:

      System.out.println("Friday");

      break;

    case 7:

      System.out.println("Saturday");

      break;

    default:

      System.out.println("Wrong option");

      break;

     }  

  }

}

Output of Program: When there is a matching switch case.

When there is no matching case the default code block will execute.

JAVA Programming : If Statement

2011-06-20T11:35:00.000-07:00

JAVA If Statement

The If statement may be defined as a decision making statement, a control flow statement or a selection statement. In a simple program the execution of code starts form first line and ends at the last line but what if we want to execute a block of code only under a certain circumstances. The if statement is the simplest decision making statement. An If statement evaluates a Boolean expression (true or false) and determine whether to run a particular set of statement or not. The syntax of an if statement is:

 if (booleanExpression) {  

      //set of statement 

}

Example of If Statement: Using If statement to find out whether a number is divisible of 5 or not.

 public class IfStatement{

   public static void main(String args[]){

    int x=15;

    if(x%5==0){

      System.out.println("x is divisble by 5");   

    }

   }   

}

If-Else Statement:- An If statement runs a block of code if the testing condition is true. By using If-else statement we can give another another block of code that will run when the If condition is not true. In other words in If-Else statement code in If block will run when condition is true and code in Else block will run when condition is false. Below is the syntax of If-Else statement.

 if(booleanExperssion){   

  //set of statement

}

else{

  //set of statement

}

Example of If-Else Statement: In this example we will find weather a number is odd or even using If-Else Statement. As we know if a number is divisible by 2 then it is an even number else it is an odd number.

 public class IfElseStatement{

  public static void main(String args[]){

    int x=5;

    if(x%2==0){

      System.out.println("x is an even number");   

    }else{

      System.out.println("x is an odd number");

    }

  }   

}

If Else If Statement: If-Else-If Statement is used when we have to choose form multiple course of action or we can say If-Else-If Statement is used when we have to check multiple conditions and there is different course of action for every condition. Let’s understand it with an example where we have to set student’s grade on the basis of marks.

 public class IfElseIf{

  public static void main(String args[]){    

    int

marks=85;

     char grade = ' ';

    if(marks >= 90){

      grade = 'A';

    }

    else if (marks >= 80){

      grade = 'B';

    }

    else if (marks >= 70){

      grade = 'C';

    }

    else if (marks >= 60){

      grade = 'D';

    }

    else{

      grade = 'E';

    }

  }   

}

In If-Else-If statements once a condition is found true that particular block of statement are executed and rest of the condition will not be checked. For example when first If condition is found true, it will not check the rest of the Else If or else statements otherwise it will check the second Else If and so on.

In this example, marks are 85 therefore it satisfies more than one given conditions which is greater than equal to 60, greater than equal to 70 and grater than equal to 80. But when the first else if which is greater that equal to 80 found true it will not check the remaining conditions and the grade will be set to B which is the correct grade. But here you can notice a wrongly formatted code can lead to an error. Lets take a look at the code below:

public class IfElseIf{

  public static void main(String args[]){    

    int

marks=85;

    char grade = ' ';

    if(marks >= 60){

      grade = 'D';

    }

    else if (marks >= 70){

      grade = 'C';

    }

    else if (marks >= 80){

      grade = 'B';

    }

    else if (marks >=

){

      grade = 'A';

    }

    else{

      grade = 'E';

    }

  }   

}

In this program as the first if condition is true the grade will be set to D and rest of conditions will be ignored. But the correct grade should be B as the marks scored are more than 80. So now we can see if the program is not correctly formatted it can lead to errors. This problem can be solved using multiple condition in one If block using logical operators like || and &&.

 public class IfElseIf{

  public static void main(String args[]){

    int marks=85;

    char grade = ' ';

    if(marks >= 60 && marks < 70){

      grade = 'D';

    }

    else if (marks >= 70 && marks < 80){     

      grade = 'C';

    }

    else if (marks >= 80 && marks < 90){

      grade = 'B';

    }

    else if (marks >= 90){

      grade = 'A';

    }

    else{

      grade = 'E';

    }

  }   

}

Here by giving multiple conditions using logical operators we can make sure that the code will result in correct output even if the code is not correctly formatted.

JAVA Programming : Operators

2011-04-22T05:37:00.000-07:00

JAVA Operators

A Operator in Java is a Symbol that manipulates one or more primitive data types (arguments) to produce a result. Operators are very important part of Java programming. Below is the list of Operators available in Java.

OPERATORS
Assignment Operators	=

Arithmetic Operators	-	+	*	/	%	++	--

Relational Operators	>	<	>=	<=	==	!=

Logical Operators	&&	\|\|	!

Bit wise Operator	&	\|	^	>>	>>>

Compound Assignment Operators	+=	-=	*=	/=	%=

Conditional Operator	?:

Assignment Operator: It is the most common and simple operator that is used to assign value on its right to the operand on its left.

Arithmetic Operators: As the name suggest these are the operators that are used for performing arithmetic operations. Java provide seven arithmetic operators add, subtract, multiply, divide, mode (returns remainder), unary increment and unary decrement.

Bit Wise Operators: Bit operator in Java are use to manipulate variables at bit level. It is not recommended to use bit wise operatically in normal application programming because in makes code hard to understand. So, we are not going to discusses bit wise operators in details. In code below we shown how to use these operators.

Compound Operators:- Compound operators provide a short way or syntax to write Arithmetic and Bitwise operators. There are eleven compound operators in Java.

Below is the Java Code that shows how to use Assignment, Arithmetic, Bit wise and Compound Operator in a program. This Class doesn't actually do anything in terms of producing result, but it shows you the syntax to use these operators.

 public class Operators {

    public static void main(String arg[]) {



      vv//Assignment Operator

      vvint a = 1;     // a has value 1

        int b = 2;    // b has value 2

        int c = a;    // c gets the value of a i.e 1



         //Arithmetic Operators

        a = b + c;    //Addition

        a = b - c;    //subtraction

        a = b * c;    //Multiply

        a = b / c;    //Division

        a = b % c;    //Mode

        a++;      //Increment a by 1

        a--;      //Decrement a by 1

         //Bit Wise Operators

        a = a << 3;   //Left Shift 

        a = a >> 3;    //Right Shift

        a = a >>> 3;  //Unsigned Right Shift



        a = b & c;     //AND

        a = b | c;    //OR

        a = b ^ c;    //XOR



        a = a + b;  //this is normal + operation

        a += b;    //this is compound operation of above 



         //compound Operators

        a -= b;

        a *= b;

        a /= b;

        a %= b;



         a >>= 3;

        a <<= 3;

        a >>>= 3;



        a &= b;

        a |= b;

        a ^= b;

    }

}

Relational Operator:
Relational Operator in Java are binary operators i.e. they are used to compare two operands. There are six relational operators as shown above. Relational operator in java compare to numaric objects and results in a boolean value.

 public class Relational{

   public static void main(String args[]){



     int a = 20, b = 10;



     System.out.println("a > b results in : "+(a > b));

     System.out.println("a < b results in : "+(a < b));

     System.out.println("a >= b

results in :  "+(a >= b));
     System.out.println("a <= b results in :  "+(a <= b));
     System.out.println("a == b results in :  "+(a == b));
     System.out.println("a != b results in :  "+(a != b));

Logical Operator:
Logical operator evaluates two Java boolean values and gives results in boolean value. There are three logical operator in Java. Below is the code that shows the basics of logical operators.

 public class Logical{

   public static void main(String args[]){

     boolean a = true;

     boolean b = false;



      System.out.println("a && b

results in : " + (a && b));
System.out.println("a || b results in : " + (a || b));
System.out.println("!a results in : " + (!a));

    }

}

Truth table for and or and not operations: Here P and Q are Boolean expressions and T stands for true and F stands for false.

Conditional Operator:
Conditional Operator is a ternary operator in Java which evaluates a expression and returns option1 if result is true else returns option2. Take a Look at the figure below.

public class Conditional {

   public static void main(String args[]){   

     int a=5;

     int b=10;

     int max;



     max= a > b ? a : b ; 

     System.out.println("Max = "+max);

   }

}

JAVA Programming : Using Scanner for User Input

2011-04-16T13:05:00.000-07:00

JAVA Scanner

As we now know a little bit about Java programming we will start making our first program. In this tutorial we learn how to get input from user. There are a number of ways for taking input form user in Java and one way is using Scanner. A Scanner class is already built in Java and present in the java.util package. A scanner takes input from various types of Input Streams.

Creating a Scanner Object:
Lets create a scanner object that accepts systems.in as input stream it means that scanner will take input from console.

Scanner scan = new Scanner(System.in); // System.in is an InputStream

A scanner can take various types as input stream for example, here we have a File Reader as input stream that reads data from a file named as MyFile.

Scanner scanfile = new Scanner(new FileReader("MyFile"));

Getting User Input form Console using Scanner : Lets create a class that take two integer input from user and prints their sum. To use the Scanner class, first we need to import it. Take a look at the code :

 import java.util.Scanner;



public class UserInput {

  public static void main(String args[]){  

    int second ;

    int first;

    int total;

    Scanner scan = new Scanner(System.in);



     System.out.println("enter 1st no.");

    first = scan.nextInt(); //stores user input into first          



     System.out.println("enter 2nd no.");

    second = scan.nextInt(); //stores user input into second



     total = first + second ;  //sum of first and second  

     System.out.println("sum = "+ total); 

   }

}

In the first line of code, we have an import statement to import Scanner class. Now we can use the Scanner class anywhere in our code. In our class we have three int variables first, second and total. Variable first and second will hold the user input and total will hold their sum.

To take integer input scanner has a method called nextInt. This methods reads the integer input by user. In the above code we have used this method two times and to save user input in int variables first and second.

Output of Program :

Note that if are using nextInt method and the input given is not integer, then compiler will give an error. There are some other methods that are used for different types of input.

Method	Reads
int nextInt()	Reads the next input as an int. If the input is not an integer,InputMismatchException is thrown.
long nextLong()	Reads the next token as a long. If the next token is not an long,InputMismatchException is thrown.
float nextFloat()	Reads the next input as a float. If the input is not a float, InputMismatchException is thrown.
double nextDouble()	Reads the next input as a double. If the input is not a double, InputMismatchException is thrown.
String next()	Finds and returns the next complete token from this scanner and returns it as a string; a token is usually ended by whitespace such as a blank or line break.
String nextLine()	Reads the rest of the current line, excluding any line separator at the end.
void close()	Closes the scanner.

JAVA Programming : Interface

2011-04-16T11:16:00.000-07:00

JAVA Interface

Interfaces are declared using the interface keyword and they are like a pure abstract class i.e. every method in an Interface is an abstract method. An interface can not be instantiated they can only be implemented by other classes or can be extended by other interfaces.

Implementing a interface by a class is like making a contract that the class will implement all the methods of that interface. If a class does not implement all the methods of an implemented interface, the Java Compiler will give an error.

Syntax of a Interface:-

 [access identifier] interface InterfaceName [extends Interface1, Interface2....]

{

     //adstrace method declarations

}

NOTE: Because all methods in an interface is abstract by definition so their is no need to declare them abstract by using abstract keyword.

Declaring a Interface:-

For example, lets create a interface Record which has three methods add, update and delete.

 public interface Record {          

     public void add();

    public void update();

    public void delete();

 }

Lets create a class Employee that implements the interface Record. Employee class must implement all the methods of Record interface.

 public class Employee implements Record {

// fields and methods of class

  // methods of Record interface 

  public void add() {

    // set of java statements 

   }

   public void delete() {

    // set of java statements 

   }

   public void update() {

    // set of java statements   

  }



 }

JAVA Programming : Abstract Class and Abstract Method

2011-04-12T10:36:00.000-07:00

JAVA Abstract Classes and Abstract Methods

Abstract Class: An abstract class is declared using abstract keyword. An abstract class is a class definition that is incomplete in the sense that it has some abstract methods. It is not compulsory that an abstract class has an abstract method but if a class has an abstract method, the class has to be declared as abstract. Abstract classes can never be initiated but they can be subclassed.

Abstract Method: Abstract method are declared using abstract keyword. Abstract methods are defined as part of the class but the inner workings (body of methods) are not provided. Abstract methods ends with semicolon instead of curly brackets.

   public abstract class Bike {       

        abstract void gear();

       abstract void topSpeed();

}

Why we need an Abstract Class: This is the question that many people ask about, what is the need of abstract class. The idea behind an abstract class is putting common functionality to an abstract class that other classes will extend.
For example we can have a abstract class named fan with a method for turning the fan on and off but not defining the procedure to do that i.e. with no body declaration. Now we can extend the fan class into table fan and define on and off procedure accordingly or we can extend the fan class to ceiling fan and define on and off procedure according to ceiling fan.

JAVA Programming : Variables and Scope of Variables

2011-04-11T09:21:00.000-07:00

JAVA Variables

A variable in Java is like place holder that can store a value that once declared can be used through out the program according to scope of that variable(discussed below). Datatypes specifies what kind of data each variables will store for example a variable declared as int cannot have char values.

 public class DeclareVariables {



     public static void main(String args[]){  

          int a=7;

          int b=9;

          int sum;

           sum = a+b;

          System.out.println("sum = "+sum);

    }

}

In DeclareVariable class, inside the main method we declared three int variables a, b and sum. Here a and b variables has some value stored and variable sum will have their addition stored in it. Output of this Java program is:

Scope of Variables: Scope of variables is the portion of program where a declared variable can be used. Scope of Variable differ according to the place where the variable is declared. A variable can be declared in various places in a Java Class.

Class Body
Method Body
With in Statement Block
As Parameter or in for loops

First three declared variables will have there scope with in the block (curly brackets) they are declared. The variable declared as parameter or in for loops are declared with in Parentheses and can be used with in the followed statement block.

 public class ScopeOfVariables {



         public static void main(String args[]){           

                for(int a=1; a<=5; a++){

                    System.out.println(a);

               }

         }

}

In above example we have a variable declared in for loop that can used only with in the statement block of that for loop.

JAVA Programming : Data Types

2011-03-21T05:05:00.000-07:00

JAVA Data Types

Java has a number of data types below is the complete list of them . Although syntax of Java is largely derived from C++ but datatypes are a bit different from C for example C does not have Boolean data type. Java Datatypes have a fixed size and also some default values that will bet set to variables if they are declared but not initialized.

Boolean : Boolean datatype does not have a specific size declared but conceptually it has one bit value. Boolean datatypes has only two possible values true or false. Default value for Booleans are false.
Size:- not defined
Values:- true or false
Default value:- false
Char: A char is 16 bit value that can be treated like an integer value but is intended to hold characters. In a Java program a char datatype is always interpreted as a numeric value of a displayable character.
Size:- 16 bit
Values:- from 0 to 65535
Default value:- 0
Byte: A byte is an 8 bit integer value.
Size:- 8 bit
Values:- from -128 to 127
Default value:- 0
Sort: A sort is an 16 bit integer value.
Size:- 16 bit
Values:- from -32768 to 32767
Default value:- 0
Int: A int is an 32 bit integer value.
Size:- 32 bit
Values:- from -2147483648 to 2147483647
Default value:- 0
long: A Long is an 64 bit integer value and it is the largest of all the integer types.
Size:- 64 bit
Values:- from -9,223,372,036,854,775,808 to 9,223,372,036,854,775,807
Default value:- 0
float: A float is 32 bit single precision floating point decimal number.
Size:- 32 bit
Values:- from -1.4E-45 to 3.4028235E38
Default value:- 0.0
double: Double is 64 bit double precision floating point decimal number.
Size:- 64 bit
Values:- from -4.9E-324 to 1.7976931348623157E308
Default value:- 0.0

JAVA Programming : Hello World

2011-03-18T14:50:00.000-07:00

JAVA Hello World Program

A Java Hello World program is the traditional program that you will find everywhere on the web and this program is probably the simplest program that you can write and make it actually do something. Hello World program doesn't do much, it just displays one line of text on the screen but it is a complete java program that will actually compile and run.

Source Code of Hello World Java program:



   public class HelloWorld {



       public static void main(String args[]){       



           System.out.println("Hello World");   //prints a line on screen 

       }



   }

A Closer look at Hello World Program :

The first line of the code declares a public class named HelloWorld. Declaring a class public means that it can be accessed by name form any place (talk more about Access specifiers letter). In second line we declare a main method. Every class file that can be executed form command line should have a main method just like this one. When ever we run a Java program the compilers looks for a main method to starts with. A main method is always declared as public so that it can be accessible from any where and static so it exist without a object being created. The main method takes a string array argument as parameter. We can pass a string array from command line at the time of running java program. Now inside the main method there is only one line of code that calls to the println method that prints a line of text.

The text that written after the "System.out.println("Hello World");" is known as comment. A Comment is not part of the actual code i.e. the compiler will not compile a comment. Comments are only used for increasing the readability of code. To make something a comment use two forward slashes(//) in front of it.

JAVA Programming : Naming Rules and Conventions

2011-03-17T18:23:00.000-07:00

JAVA Naming Rules and Conventions

Before we start writing any Java Program or code we must know about some naming rules and convention of Java, so first we talk about some rules.

Java Naming Rules: Below are the set of rules that you must follow to write a error free code.

Java is Case Sensitive language that means that upper case latter and lower case latter are two different things. In other words we can say that in Java there are 52 characters (26 upper and 26 lower case). For example JAVACODESPOT , JavaCodeSpot and javacodespot will be treated as different identifiers in Java.

First Character of any name can be any of these:

a-z (any lower case alphabets)

A-Z (any lower case alphabets)

$ (A dollar sign)

_ (Underscore sign)

Note: the first character of any name can not be digit (0-9)

After first character a name can be anything that a first character can be and it can have a digit or number (0-9) also.

Java Naming Conventions: Bellow are the set of standards that are given by Sun that programmer should follow to make their code easier to read for themselves and for other programmers.

For Classes and Interfaces the first letter of the name should be capitalized and if the name is made up with several words, start of every word should be capitalized for example Dog, CamelCase.

For Methods and Variables the first word of the name should be lowercase and if the name is made up with several words, start of every word except first word should be capitalized for example dog, camelCase.

For Constant there is no predefined type in Java but you can have a constant by declaring variable static and final. A Constant name should be of uppercase and if the name is made up with several words the underscore should be used between the words for example DOG, CAMEL_CASE.

For Packages names should be in lowercase and full stop (.) as separator.

JAVA Programming : Methods

2011-03-17T13:26:00.000-07:00

JAVA Methods

A Java method contains set of Java statements which is declared inside a Java class. Methods are where class logic is stored or where the actual work gets done. Java methods are similar to functions or procedures in other programming languages.

A Java method declaration various parts like Modifiers, Return Type, Method name, parameter and and there is one more thing exceptions that can also be part of a method.

Syntex of a Java Method :

   Modifier ReturnType MethodName ( Parameters ){
   // set of java statements
   }

Example of a Java Method :

   public int giveSum (int a, int b){       



    int ans = a + b;

    return ans;  



  }

Once a method is defined, it can be called with in a Java class just by writing name of the method followed by parameters in the brackets according to method definition and followed by a semicolon. For example if above method giveSum is to called then :

giveSum(10,20); //calling a method

JAVA Programming : Object

2011-01-30T12:18:00.000-08:00

JAVA Objects

As you know from the previous post, class is a blueprint for object. So, an Object is an instance of class that Java Virtual Machine (JVM) create at runtime whenever it finds an new keyword. Every object will have state and behavior defined in its class.

To understand software objects, first we look at some example of real world object like a Fan. A fan will have its own state like motor, blade, power switch etc. and behavior like speed, on or off etc. In the same way there are software objects that too have state in form of fields or variables and behavior in form of methods or functions.

Creating an Object:
For example we take a Television class and create its object.

public class Television {



    // the Television class has two fields

    public int size;

    public String  colorType;



    // the Television class has one constructor

    public Television(int tvSize, String tvColorType) {



        size = tvSize;

        colorType = tvColorType;

    }

}

A object of television class can be created in this way:

Television tv = new Television(12,"Color TV");

In a object Declaration Statement there is three part
1. Declaration of object : Part of statement before the '=' sign is Declaration part of object.
2. Instantiation : The new keyword in Java does the instantiation of an object.
3. Initialization : After new keyword there is call to construction of class which does the initialization.

It is not necessary that declaration part is to followed by instantiation and initialization part. Like other variable declarations, object declarations can be done alone. A object declaration can be done in this way :

Television tv;

tv = new Television(12,"Color TV");

JAVA Programming : Class

2011-01-19T05:34:00.000-08:00

JAVA Class

Class in Java is a template that describes the kind of state and behavior that objects of its type support. In simple words a Class is an blueprint from which an object is constructed.

For Example think of a Blueprint of a house. A class for an object is like a blueprint for a house. A blueprint can be used to build a lot of hoses and a class can be used to build a lot of object.

Things defines inside the class are said to be member of the class and when the objects are constructed from the class, the member of class also become member of each object.

A Class declaration can be done in this way:

 public class Television {



     // the Television class has two fields

    public int size;

    public String  colorType;



     // the Television class has one constructor

    public Television(int tvSize, String tvColorType) {



        size = tvSize;

        colorType = tvColorType;

    }



     // the Television class has two methods

    public void setSize(int newValue) {



        size = newValue;

    }



    public void setColorType(String newValue) {



        colorType = newValue;

    }

 }

Java Subclass :
Subclass in Java is a class that is an extension of an existing class. In other words Subclass is a class that extends another class. A Subclass is also known as Derived Class or Child Class.
A Subclass will inherits all properties like variables and methods of Extended Class or Super Class.
For example, we make a Class LcdTv which extends the class Television. Now the LcdTv class will have all the properties of Television so we don't need to write them again but LcdTv class has one extra property contrastRatio that is not present in Television Class, so we need to declare that field in LcdTv class.

public class LcdTv extends Television {

  

    // the LcdTv subclass has one field

    public String contrastRatio;



    // the LcdTv subclass has one constructor

    public LcdTv(int tvSize, String tvColorType, String tvContrastRatio) {   



        super(tvSize, tvColorType);

        contrastRatio = tvContrastRatio;

    }  



    // the LcdTv subclass has one method

    public void setHeight(String newValue) {



        contrastRatio = newValue;

    }  



}

JAVA : Version Checker

2011-01-02T11:46:00.000-08:00

JAVA Version Checker

What Version of Java is Running on your System?

To Know answer that Java Code Spot has wrote a simple Java Version checker Application that tells what version of Java is currently running on your system. Your system has the information about the version of Java installed and you can get that inforamtion for Java Runtime Enviornment of your system. Version checker Applet also displays some other information like Vendor of Java, Operating system, OS Version and OS Architecture.

!!!!!!!!!!....Applet may take some time to load....!!!!!!!!!!

If You have Java installed and enabled in your browser you will see a pink color rectangle above with information displaying. If you don't see a pink rectangle it means Java may not be installed.

In this application we are getting information about Java and Operation System by a simple code
System.getProperty(String Key);

This method is used to get System properties according to parameter given in String.

Java Code to get System Information:

System.getProperty("java.version");

System.getProperty("java.vendor");

System.getProperty("os.name");

System.getProperty("os.version");

System.getProperty("os.arch");

You can also get some other information using this method

S/No. Key    Description
---------------------------------------------------------------------------------------------------------
1    java.version    The version of Java Runtime Environment.
2      java.vendor    The name of Java Runtime Environment vendor
3      java.vendor.url    The URL of Java vendor
4    java.home    The directory of Java installation

5 user.name The name of account name user

6 user.home The home directory of user

7 user.dir The current working directory of the user

8      java.vm.version    JVM implementation version
9      java.vm.vendor    JVM implementation vendor
10    java.vm.name    JVM implementation name
11    java.specification.version    The name of specification version Java Runtime Environment
12    java.specification.vendor    JRE specification vendor
13    java.class.version    Java class format version number
14    java.class.path    Path of java class
15    java.library.path    List of paths to search when loading libraries
16    java.io.tmpdir    The path of temp file
17    java.compiler    The Name of JIT compiler to use
18    os.name    The name of OS name
19    os.arch    The OS architecture
20    os.version    The version of OS

Download Files Here:

Download Source Code of JAVA Version Checker Application (File Size: 2Kb)

JAVA : Font Formatter

2010-12-15T11:01:00.000-08:00

JAVA Font Formatter

Font Formatter is a Java application that allows user to manipulate font in different ways like font type, font size, and font style. This Font Formatter Java application shows the use of font utility that can be used in many other programs.

!!!!!!!!!!....Applet may take some time to load....!!!!!!!!!!

Instruction:-
1.) Select the type of font from the options in combo box.
2.) Select the size of font form the second combo box.
3.) Check or uncheck the Bold or Italic check box to change the style of font.
4.) Press Quit Button to Quit.

Available fonts:
To get the available fonts list in Java a toolkit object is used. A toolkit object contains the list of the available fonts which can be fetched using a in build method.

String[ ] fontList;
fontList = Toolkit.getDefaultToolkit().getFontList();

In this program a createFontChoice() function is written for making a combo box list of available fonts.

private void createFontChoice() {

fontChoice.addItemListener(this);
String[] fontList;
fontList = Toolkit.getDefaultToolkit().getFontList();
for(int i=0; i<fontlist.length; i++){
fontChoice.addItem(fontList[i]);
}
fontName = fontList[0];
}

Download Files Here:

Download Source Code of Font Formatter JAVA Application (File Size: 5Kb)

JAVA : Paint Application

2010-12-01T09:46:00.000-08:00

JAVA Paint Application

Java Paint application is a simple applet implementation of MS paint like application implemented in Java written by Java Code Spot which allows user to draw different shapes and basic drawing. It has the basic drawing tools such as point, line, rectangles, round rectangles and circles and color manipulation options, other than that it has eraser tool. Paint application is a good example of how to use java's graphics libraries.

!!!!!!!!!!....Applet may take some time to load....!!!!!!!!!!

Instruction:
1)Select the drawing tool from the combo box.
2)Check draw or fill option to choose how to draw.
3)Check eraser option for using eraser tool.

4)Choose color of drawing from color combo box.

5)Press 'z' for undo.

Download Files Here:

Download Source Code of Paint JAVA Application (File Size: 9Kb)