Head First Java Chapter 3


    In this chapter I learned about primitive and reference variables. Primitive variables values are the bits representing the value. While a reference variable value is the bits representing a way to get to an object on the heap. A reference variable is null when not assigned an object. I learned about creating an array of variables and how it is always an object. I copied this code for a dog program. However, I moved the main method into its own class and put the dog class in a new file. I changed the second line to clarify what the dogs name on the last line was and fixed some grammar.

Dog Program:

Main File:

























Dog File:

Output:

Head First Java Chapter 2

    In this chapter I learned about the advantages of object oriented (OO) programing and what exactly it is. This chapter was sort of dull when it came to information about coding, but it had a lot of info on object oriented programs. Object oriented programing is different from procedural programing because with object oriented you think of the things in the program and in procedural you think of the things the program has to do. The main advantage OO has over procedural is that you don't have to edit existing code to add features or things. On the other hand procedural is usually faster to make. I also learned about how a class and a object can inherit methods and instance variables from a superclass or a class respectively.

Head First Java Chapter 1

    I read through chapter 1 and did the activities. In this chapter I learned the basics of java. I had no idea that in order to put an else with an if statement you must put it on the same line after the ending '}'.
Like This: 

if (x == 5) {
System.out.println("X = 5");
} else {
System.out.println("X != 5"):
}

    I also learned that empty space doesn't matter and every statement must end in a semi-colon. I leaened the basic structure of a java program which is class-method-statement.

x == 5 or x     ==     5
System.out.println("hi");

    I thought this was the mistake in the Beer program. I had to look back through the chapter to see this. I also learned the basic structure of a java program. The class is used to hold methods, which hold statements. You need a main method in order to start your program. 

    I fixed the Beer program by changing the if statement at the end and adding two if's inside the else. The problem was that one line printed "1 bottles of beer on the wall" which is not proper English. This was partially dealt with towards the beginning of the original program.

package javaapplication1;

public class BeerSong {

    public static void main(String[] args) {
        int beerNum = 99;
        String word = "bottles";
        
        while (beerNum > 0) {
            if (beerNum == 1) {
                word = "bottle"; //Changes bottles to singular if only 1.
            }
            
            System.out.println(beerNum + " " + word + " of beer on the wall");
            System.out.println(beerNum + " " + word + " of beer.");
            System.out.println("Take one down.");
            System.out.println("Pass it around.");
            beerNum = beerNum - 1;
            
            if (beerNum > 1) { //Had to change to 1 to not print '1 bottles of beer...'
                System.out.println(beerNum + " " + word + " of beer on the wall");
            } else {
                if (beerNum == 1) { //Added to make bottles singular when only 1.
                    System.out.println("1 bottle of beer on the wall");
                }
                if (beerNum == 0) { //Moved from original location to this if statement.
                    System.out.println("No more bottles of beer on the wall");
                }
            }
        }
    }

}