What the JAVA?

TwoArrays in Java

2011-05-28T23:08:00.000-07:00

Two Arrays in Java:Sample program

        public class TwoArrays {

       public static void main(String[] args) {
       int val[] = {13,-4,82,17};
       int twice[] = new int [4];
       System.out.println("Original Array: "+ val[0]+","+val[1]+","+val[2]+","+val[3]);

       //the next line of coude would doulbe the values of val and assign them to twice

        twice[0] = val[0]*2;
       twice[1] = val[1]*2;
       twice[2] = val[2]*2;
       twice[3] = val[3]*2;
      System.out.println("New Array: "+ twice[0]+","+twice[1]+","+twice[2]+","+twice[3]);

//another way to do it
        twice[0] = val[0]+val[0];
       twice[1] = val[1]+val[1];
       twice[2] = val[2]+val[2];
       twice[3] = val[3]+val[3];
System.out.println("New Array: "+ twice[0]+","+twice[1]+","+twice[2]+","+twice[3]);
    }

}

Array Sum Activity in Java

2011-05-28T22:57:00.000-07:00

//here is an Array Sum sample Activity in Java
public class ArraySum {

       public static void main(String[] args) {
               int[] val = {0, 1, 2, 3};
        int sum = 0;
        sum = val[0] + val[1] + val[2] + val[3];
        System.out.println("Sum of all numbers = " + sum);
    }
}

Array Length in Java

2011-05-28T22:41:00.000-07:00

Array Length in Java

In order to get the number of elements in an array, you can use the length field of an array. The length field of an array returns the size of the array.

Syntax:

arrayName.length

Example:

int[] num = new int [100];

for (int counter = 0; counter<num.length; counter++)

{

System.out.print(num[counter]);

}

Initializer Lists in java

2011-05-28T08:43:00.000-07:00

Initializer Lists in java

In Java you can declare, construct and initialize an array all in one statemet:

int[] data = {23, 38,13,22,-3,0,-25}; //I honestly prefer Initializing Arrays this way

int[] data = new int []{23, 38,13,22,-3,0,-25};

Using a Variable as your index in java

2011-05-28T08:37:00.000-07:00

Using a Variable as your index in java

sample code:

int x[] = new int [3];

int index;

index = 0;

x [index]= 1; //this places 1 into x[0]..

index = 2;

x[index] = 10; //this places 10 int x[2]..

index = 3;

x[index] = 20;

//this is an error.. because index 3 is already out of bounds. because you declare x with 3 slots, you are only limited until x[2]..

Array Bounds Checking

2011-05-28T08:25:00.000-07:00

Array Bounds Checking

- The length of an arra is how many slots it has. An array of length Number for example has slots indexed 0- (Number -1).

-All indexes should be of Integer type.

-Every-time your compiler says the error. System Out of Bounds something like that. You should automatically know that the problem is with your array. don't waste your time by reading all-through-out your program.

Declaring Arrays

2011-05-28T08:11:00.000-07:00

Declaring Arrays

Arrays must be declared like variables. When declaring an array, you list the data type, followed by a set of square brackets [], followed by the identifier name.

Example:

int[] ages; or int ages[];

After Declaring, create the array and specify it's length with a constructor statement. This process in java is call instantiation. In order to instantiate an object, use a constructor.

int ages[];

//you declare an array with data type int and identifier ages

ages = new int [100]

//you declared that ages should contain 100 slots.

or you can put-up the two code lines together just like this:

int ages[] = new int [100];

Arrays Defined

2011-05-28T07:57:00.000-07:00

Array Defined

An Array stores multiple data items of the same datatype, in a contiguous block of memory, divided into a number of slots.

Array is an object that is used to store lists of values. It is made out of contiguous block of memory that is divided into a number of slots. Each slots holds a value and all slots has the same data type.

         - Arrays have indexes
         - Indexes are used to access any of the slots.