Daddy The Father

Programming Methodology Lecture 16 and 17

2012-03-04T05:24:00.002-08:00

This week was a little busy but it will soon not be so busy. The school year will end in a few weeks. I had my last 6th grade lesson last week. But the homeroom teachers were not in both of them so I don't think it went like it should have. But I was happy that some students thanked me outside of the class and said that my class was fun.
Lecture 16 is about arrays. Arrays are ordered and homogeneous in Java. Homogeneous means everything is of the same type. We declare an array like:
   int[] myArr = new int[5];

Arrays will start initialized. For example int arrays will be initialized to 0. On the other hand objects are null. Array indexing starts at 0 and goes to n-1 where n is the number of elements in the array.
Mehran goes on to explain post-incrementing and pre-incrementing and their usefulness with arrays.
   example: mid[numScores++] = score;

He then goes on to explain the actual size of an array vs the effective size. Actual size is the declared size. Effective size is how much is really used.
In Java the size of the array can be dynamic - given at runtime.
Arrays can also be more than one dimension.
For example,
   int [][] matrix = new int[2][3];

one useful method:
   a.length

After that he begins to explain ArrayList. We must
   import java.util.*;

ArrayList uses template
   ArrayList <String> strList = new ArrayList<String>();

ArrayList holds objects

Programming Methodology Lecture 15

2012-02-25T23:51:00.001-08:00

Have been watching One Piece in between studying. I'm aorund the Davy Back Fight part. It's not as interesting to me. But I like One Piece overall. I was more addicted to it but now don't watch as much. It will still be a long time until if finishes anyway so I should slow down on the episodes.

In Lecture 15, Mehran starts with a review of memory and pointers. Again, objects are passed by reference. We must be careful about a null dereference:
   Point p3;
   p3.Move(3,4); // error null dereference

So primitive types are passed by value and objects are passed by value.  Primitive types do have a class version:
   int --> Integer
   double --> Double
   boolean --> Boolean
   char --> Character

After the review, he begins to talk about Files.
Files uses import java.io.*;

Reading files:
   1. Open
   2. Read file (line by line)
   3. Close

example:
   BufferedReader rd = new BufferedReader(new FileReader("students.txt"));
   while (true) {
      string line = rd.readLine();
      if (line == null)
         break;
  }
   rd.close();

He then talks about exceptions. Throwing:
   try {
         //code for file access
   } catch (IOException ex) {
         //deal with exception
   }

Writing Files:
   1. Open
   2. Write //   ____.println
   3.  Close

Programming Methodology Lecture 13 and 14

2012-02-25T21:39:00.001-08:00

Lecture 13 was something I understood. Mehran explains string functions.
String indexing starts at 0.
str.substring(0,end) //is a substring from 0 to end-1
He explains tokenizers
we must import java.util.*; for string tokenizer

Lecture 14 is important. It is about memory and he explains how it works in Java.

First, he briefly explains bits, bytes, word, kilobyte, M, G, T,...
He then explains about hexadecimal (base 16). This is used for memory addresses

Static variables and constants are special for memory

Dynamic variables use heap //dynamic is anything that uses the new keyword
He explains the stack and the heap
The heap goes downward and the stack goes upward. If they meet we might have a crash
The heap starts with a low memory address (0000)
The stacks starts with a high one (FFFF)

He explains memory allocation. When a variable goes out of scope, the memory is released (popped off the stack).

Programming Methodology Lecture 10 and 11

2012-02-25T20:29:00.001-08:00

It seems I forgot to write about Lecture 10 and 11.
This week was a little busy but it should get better soon. I only have about 2 weeks of lesson at the elementary school and then 2 weeks of boring free time but maybe I can study more then.
Yesterday, I bought a new Softbank smart phone. I bought it through their online shop. It's much better because there is no sales pressure and upsells. The downside is that there is no immediate gratification. But I can wait. I will be getting a Sharp Aquos 104SH smart phone. It has one of the best specs right now. It was a little expensive but I don't plan to use the data plan so maybe it will be ok.
Lecture 10 was not so interesting for me. Do I use the word interesting too much? I was told by a housemate before that I did.
In the lecture, Mehran starts by reviewing classes. He says that we need getters to access private variables and that the getter is public.
We can extend classes:
   super calls constructor of extended
   we can also override methods
When we pass an object as a parameter, we pass its refrence not a copy of the object. So we have to be careful. This is different than for primitives (int, char, double, ...)

After that, he explains Javadoc documentation.
Javadoc comments:
   start with: /**
   end with: */
   special tags: @param, @result
Javadoc comments are useful because we don't have to look at the code.
He then talks about Graphics. I think this is important because many things use graphics nowadays. Although Java graphics don't look so nice to me. For graphics, we should import acm.graphics.*
for this:
   it's a collage model
   we create an image by adding objects to a canvas
   newer objects obscure those added earlier
   layering is called the stacking order (or z-order)

After that, he explains a little about Interfaces. An interface is a set of methods and a set of classes that have that set of methods.

In Lecture 11, Mehran talks more about graphics:
   GCompound- allows for combining several graphics objects so they behave like GObject

He then explains Event-driven programs. These involves the mouse or keyboard
We can respond to events by having the listerner for events:
   addMouseListeners();
   addKeyListerners();
We must use the Java library that adds events:
    import java.awt.event.*;

For asynchronous events - we don't know when they will happen

Programming Methodology Lecture 12

2012-02-20T03:18:00.000-08:00

I haven't been motivated recently. I have been thinking about my spring vacation instead. I plan to go to Vienna, Copenhagen, and Texas for my spring break. I will finish my contract at the end of March as an elementary teacher. After that, I intend to collect unemployment benefits for 3 months. During that time, I will study more about programming too.
Lecture 14 was not so interesting for me. Mehran begins by explaining enumeration.
Enumeration is a
   - set of numbers
   - set of items that go together

He gives an example of enumeration using the switch statement in Java.

Next, he talks about char.
char uses single quotes:
   'a' ... 'z'
   '\n' '\t'

All chars have a sequential ASCII code.

Here's some example code:
   String s = readLine();
   char ch = s.charAt(0);

He gives example code to switch an upper case letter to lower case:
   public char toLower(char ch)
   {
      if (ch >= 'A' && ch <= 'Z') {
         return (ch - 'A' + 'a');}
      else
          return ch;
   }

He then talks about strings. Strings are immutable in Java. String concatenation is ok using +.

To check string equality use:
   s1.equals(str); // not ==

Programming Methodology Lecture 9

2012-02-11T01:28:00.000-08:00

So today, I am on a mattress run/staycation. I guess most people don't know what a mattress run is but it is staying at a hotel to get points or miles for future stays. It is at the Hilton Narita. Narita is an okay city to visit once. It has a nice temple and touristy shops near the station. There is also an Aeon Shopping mall we can reach by bus. The mall is not so interesting though.
In Lecture 9, Mehran says this is an important lecture. He first introduces string concatenation.
Example:
String str = "hello there";
String name = "Bob";
int age = 20;
String s = "Name: " + name + "Age: " + age;

After that, he introduces classes. This is the important part he says. The format for a class is:
public class name extends superclass { //extends superclass is not necessary
...
}

this will be saved as classname.java

He then explains a little bit about using Eclipse.

He talks about constructors and overloading
- the name of class is used as a constructor name
- the constructor does not specify return type
- responsible for initializing object

he then explains this. example:
this.counter = counter;
- this refers to the receiver object
- automatically available to methods of a class
- better to not use this cause less buggy
He says it's better to not use this.

He explains that when we pass an object as a parameter, we pass its reference not a copy of the object. As opposed to int, double, ... where it's not by reference

A class variable is a variable that is shared by all objects of that class (they all refer to the same variable). Example:
private static int counter; // static is the different part

This is different than an instance variable

He then explains Javadoc documentation. Javadoc comments:
start with /**
end with */
-special tags @param, @result ...
This is useful because we don't have to look through code to figure out what something is doing.

Programming Methodology Lecture 8

2012-02-09T03:30:00.000-08:00

As I think I mentioned before, I am not talking to my mother. But since I'm not talking to her I can't really talk to the rest of my family. I have one issue though. My mail is being sent to my home there and I don't want it to be. There are many issues though about mail forwarding or getting a mail box in Japan. I need to renew my driver's license soon so this is kind of important. I need to decide soon what to do. Any benefactors out there want to help a closeted gay guy?
In Lecture 8, Mehran first talks about information hiding. We should do this as much as possible.
He defines:
client of a class = user of a class
implementor = coder

He then speaks bout RandomGenerator

He describes an instance variable ("ivar") as something that is declared in a class but not in a method. This is visible in entire object. Constants are also instance variables.
On the other hand we have local variables. They are declared in a method. It is visible in the method. The state should be stored.

In the end, he speaks about RandomGenerator again and he recommends using seeds for testing because we will get the same random number everytime.

Programming Methodology Lecture 7

2012-02-07T03:38:00.000-08:00

My day was okay today. My lessons were fine today. I ate lunch with a fourth grade class and I enjoyed chatting with them. But I really don't like teaching that class. I was surprised that one of the second grade students did not know how to write arigatou in Japanese. I wonder if the bad teaching or the student.

Professor Mehran continues introducing Java syntax in this lecture.
He first says that casts are necessary for:
    int x = (int) y;

He calls the while loop the indefinite loop.

Another example he gives is that we can use:
   while(true) with a break statement

He also says that for and while loops can be equivalent. We should use the for loop if we know the number of iterations and the while loop when we don't know how many times we'll loop:

   for(init; test; step) {
      statement
   }

   init
   while (test) {
      statement
      step
   }

Next, he begins to introduce Java methods (also known as functions). We should try to break down a method into some piece that can be reusable. We should think about input and output for reuse too

Methods are called in this format:
   receiver.name(arguments)

Methods are in this format:
   visibility type name(parameters) {
      body
   }

   visibility is private or public
   type is the return value or it can be void. objects can also be returned

We define a predicate method as a method that returns a boolean

Programming Methodology Lecture 6

2012-02-06T03:49:00.000-08:00

Today I was at my other elementary school. I only teach there on Mondays but it's okay overall. The other ALT is a little crazy but he's an overall nice guy. He seems a little paranoid about things and doesn't seem to trust people. He seems like my best friend but crazier. He seems to have these theories about things that don't make sense to me.
This year my resolution was to be nicer and I think I am overall. The one thing that kind of annoys me are people on the train and at the station. I don't like when people push when they don't need to. I have to be more understanding about that.
Today's lecture was over Java basics which I pretty much knew. Some things I should remember:

remember to type cast
for example:
int x = 5;
double y = (double) x/2;

z = (int) y; //does truncation

for CONSTANTS use:
private static final double PI = 3.14;

Mehran also covers boolean, if..else, while, and for loop.

I also learned about George Boole in this lecture. He caught pneumonia by being out in the cold rain. He died because he was treated by someone who thought that they should do the same thing that got him sick in the first place. She threw cold water on him while he was in bed and he died.

Programming Methodology Lecture

2012-02-05T03:36:00.000-08:00

In this lecture, Mehran talks mostly about graphics classes and their properties

This is the GObject

If we want standard colors we should include java.awt.* package

setColor is a little different to setFillColor. Difference is the border color

we call the negative sign the unary minus

variables should have a name, a type and a value
the names should be descriptive

there are primitive types such as int, char, double, boolean

What I learned from Karel the Robot Learns Java

2012-02-05T00:51:00.000-08:00

Message - anything that triggers a particular behavior

A class is a pattern or template for objects that share a common behavior and collection of state attributes

A subclass extends a superclass

Encapsulate information - not only to gather it together but also to restrict access to that information if possible

Information hiding - hide extaneous detail to reduce complexity

decomposition - breaking a program into smaller pieces

subproblems - component parts of a large program

software engineering - programming methodologies

precondition - true before the method is called

postcondition - conditions that apply after method finishes

Programming Methodology Lecture 4

2012-02-04T22:34:00.000-08:00

In this Lecture Mehran introduces Java and kind of explains object oriented programming. I believe OOP consists of APIE, abstraction, polymorphism, inheritance and encapsulation.
Mehran first explains the difference between computer science and computer programming. CS is the study of problem solving using computational methods. Some computer scientists don't even use computers. I believe we can see this more in graduate level CS where it is a form of mathematics. Actually a lot of subjects seem to end up to be mathematics. For example physics and economics.
Computers are designed to only work with 0's and 1's or binary. But this is difficult for humans. We prefer something higher level. So we have high level langugages such as C and Java. Then the compiler takes this and turns it into something the machine can understand. In other words we make source code and it is changed to object code with a compiler.
The classical way to do this was to take source code -> compiler -> linker -> executable
But in Java it goes source file -> class file -> linker -> jar archive -> JVM

Mehran defines these things:
class - an encapsulation of behavior and data
superclass - more general
subclass - more functionality

an example of subclass and superclass is that humans are a subclass of primates

this is the class hierarchy

so we can say that subclasses inherit from the superclass

we can have an instance of a class. for example, Sean is an instance of human (Sean is an object)

First Post!

2012-02-04T18:50:00.000-08:00

Hello there!
I don't actually expect anyone to read this blog but if you do it'll be about me learning programming again. What do I mean about again? I mean that I have a computer science major but I don't think I'm that good of a progammer.
One of the biggest mistakes that I made as an undergraduate was to start the computer science program without taking the introductory course. It covered programming in C but I started with the second course. Needless to say, I was lost in that class and did not learn how to program in C until much later. Even then, I was not good at it. It took me the longest time to lean about UNIX and how to compile a program. It was still at a time when we could not find all the information we can now on the internet. Because of that mistake I was never able to really catch up in the program although I still made it through. I could make it through because I would say that I'm not stupid.
I was a math double major also. I was not such a good student. One of the problems was that I'm gay and I was having coming out issues. It was my first time away from home and I was still learning to be independent.
Another issue that I had was that I was never social. I blame that on my parents partially but that'll be a story for another day. When I found friends I was glad although it affected my study habits. I wonder if I have concentration issues but I don't know. Maybe I just want to make an excuse. I was a good student in high school overall and I did well in my classes.
So anyway this blog is a way for me to start over from the beginning. I want to do this because I want to get a job in programming. I am currently teaching English in Japan and I know that there is no future in that. I will finish my contract at the end of March and then I want to change my job. I would like to get a job from April, May or June. I hope this is not too lofty of a goal. I think I can do it if I focus.
I have started by studying along with the Stanford CS 106A Programming Methodology course available on iTunes U. It's interesting because of the Professor Mehran Sahani.
So I just finished watching Lecture 3.
Here are some things I would like to remember:
What is an algorithm vs. a program?
Decompoition - breaking down something to smaller pieces
Stepwise refinement - break down to the primitives
Top down design - start from the highest level
Bottom up design - start at the primitives
OBOG - off by one bug
For decomposition, it should solve ONE problem, be a method with 1-15 lines, have a good name and have good comments
I think we do decomposition it will be better for code reuse and also for debugging