hellojava.java

// A Single line comment

/* A 
 * Multiple line
 * comment
 */

// You can import libraries with helpful methods using import

import java.util.Scanner;
import java.util.*;

// A class defines the attributes (fields) and capabilities (methods) of a real world object

public class Animal {
	
	// static means this number is shared by all objects of type Animal
	// final means that this value can't be changed
	public static final double FAVNUMBER = 1.6180;
	
	// Variables (Fields) start with a letter, underscore or $
	// Private fields can only be accessed by other methods in the class
	
	// Strings are objects that hold a series of characters
	private String name;
	
	// An integer can hold values from -2 ^ 31 to (2 ^ 31) -1
	private int weight;
	
	// Booleans have a value of true or false
	private boolean hasOwner = false;
	
	// Bytes can hold the values between -128 to 127
	private byte age;
	
	// Longs can hold the values between -2 ^ 63 to (2 ^ 63) - 1
	private long uniqueID;
	
	// Chars are unsigned ints that represent UTF-16 codes from 0 to 65,535
	private char favoriteChar;
	
	// Doubles are 64 bit IEEE 754 floating points with decimal values
	private double speed;
	
	// Floats are 32 bit IEEE 754 floating points with decimal values
	private float height;
	
	// Static variables have the same value for every object 
	// Any variable or function that doesn't make sense for an object to have should be made static
	// protected means that this value can only be accessed by other code in the same package
	// or by subclasses in other packages
	
	protected static int numberOfAnimals = 0;
	
	// A Scanner object allows you to except user input from the keyboard
	static Scanner userInput = new Scanner(System.in);
	
	// Any time an Animal object is created this function called the constructor is called
	// to initialize the object
	public Animal(){
		
		// Shorthand for numberOfAnimals = numberOfAnimals + 1;
		numberOfAnimals++;
		
		int sumOfNumbers = 5 + 1;
		System.out.println("5 + 1 = " + sumOfNumbers);
		
		int diffOfNumbers = 5 - 1;
		System.out.println("5 - 1 = " + diffOfNumbers);
		
		int multOfNumbers = 5 * 1;
		System.out.println("5 * 1 = " + multOfNumbers);
		
		int divOfNumbers = 5 / 1;
		System.out.println("5 / 1 = " + divOfNumbers);
		
		int modOfNumbers = 5 % 3;
		System.out.println("5 % 3 = " + modOfNumbers);
	
		// print is used to print to the screen, but it doesn't end with a newline \n
		System.out.print("Enter the name: \n");
		
		// The if statement performs the actions between the { } if the condition is true
		// userInput.hasNextLine() returns true if a String was entered in the keyboard
		if(userInput.hasNextLine()){
		
			// this provides you with a way to refer to the object itself
			// userInput.nextLine() returns the value that was entered at the keyboard
			this.setName(userInput.nextLine());
			
			// hasNextInt, hasNextFloat, hasNextDouble, hasNextBoolean, hasNextByte,
			// hasNextLong, nextInt, nextDouble, nextFloat, nextBoolean, etc.
			
		}
		
		this.setFavoriteChar();
		this.setUniqueID();
		
	}
	
	// It is good to use getter and setter methods so that you can protect your data
	// In Eclipse Right Click -> Source -> Generate Getter and Setters
	
	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public int getWeight() {
		return weight;
	}

	public void setWeight(int weight) {
		this.weight = weight;
	}

	public boolean isHasOwner() {
		return hasOwner;
	}

	public void setHasOwner(boolean hasOwner) {
		this.hasOwner = hasOwner;
	}

	public byte getAge() {
		return age;
	}

	public void setAge(byte age) {
		this.age = age;
	}

	public long getUniqueID() {
		return uniqueID;
	}

	// Method overloading allows you to accept different input with the same method name
	public void setUniqueID(long uniqueID) {
		this.uniqueID = uniqueID;
		
		System.out.println("Unique ID set to: " + this.uniqueID);
	}
	
	public void setUniqueID() {
		
		long minNumber = 1;
		long maxNumber = 1000000;
		
		// Generates a random number between 1 and 1000000
		this.uniqueID = minNumber + (long)(Math.random() * ((maxNumber - minNumber) + 1));
		
		// You can cast from one primitive value into another by putting what you want between ( )
		// (byte) (short) (long) (double)
		// (float), (boolean) & (char) don't work.
		// (char) stays as a number instead of a character
		
		// You convert from a primitive to a string like this
		String stringNumber = Long.toString(maxNumber);
		
		// Byte.toString(bigByte); Short.toString(bigShort); Integer.toString(bigInt);
		// Float.toString(bigFloat); Double.toString(bigDouble); Boolean.toString(trueOrFalse);
		
		// You convert from a String to a primitive like this
		int numberString = Integer.parseInt(stringNumber);
		
		// parseShort, parseLong, parseByte, parseFloat, parseDouble, parseBoolean
		
		System.out.println("Unique ID set to: " + this.uniqueID);
	}

	public char getFavoriteChar() {
		return favoriteChar;
	}

	public void setFavoriteChar(char favoriteChar) {
		this.favoriteChar = favoriteChar;
	}
	
	public void setFavoriteChar() {
		
		int randomNumber = (int) (Math.random() * 126) + 1;
		
		this.favoriteChar = (char) randomNumber;
		
		// if then else statement
		// > < == != >= <=
		if(randomNumber == 32){
			
			System.out.println("Favorite character set to: Space");
			
		} else if(randomNumber == 10){
			
			System.out.println("Favorite character set to: New Line");
			
		} else {
		
			System.out.println("Favorite character set to: " + this.favoriteChar);
		
		}
		
		// Logical operators
		// ! : Converts the boolean value to its right to its opposite form ie. true to false
		// & : Returns true if boolean value on the right and left are both true (Always evaluates both boolean values)
		// && : Returns true if boolean value on the right and left are both true (Stops evaluating after first false)
		// | : Returns true if either boolean value on the right or left are true (Always evaluates both boolean values)
		// || : Returns true if either boolean value on the right or left are true (Stops evaluating after first true)
		// ^ : Returns true if there is 1 true and 1 false boolean value on the right or left
		
		if((randomNumber > 97) && (randomNumber < 122)){
			
			System.out.println("Favorite character is a lowercase letter");
			
		}
		
		if(((randomNumber > 97) && (randomNumber < 122)) || ((randomNumber > 64) && (randomNumber < 91))){
			
			System.out.println("Favorite character is a letter");
			
		}
		
		if(!false){
			
			System.out.println("I turned false to " + !false);
			
		}
		
		// The ternary operator assigns one or another value based on a condition
		int whichIsBigger = (50 > randomNumber) ? 50 : randomNumber;
		
		System.out.println("The biggest number is " + whichIsBigger);
		
		// The switch statement is great for when you have a limited number of values
		// and the values are int, byte, or char unless you have Java 7 which allows Strings
		switch(randomNumber){
		
		case 8 :
			System.out.println("Favorite character set to: Backspace");
			break;
			
		case 9 :
			System.out.println("Favorite character set to: Horizontal Tab");
			break;
			
		case 10 :
		case 11 :
		case 12 :
			System.out.println("Favorite character set to: Something else weird");
			break;
			
		default :
			System.out.println("Favorite character set to: " + this.favoriteChar);
			break;
		
		}
		
	}

	public double getSpeed() {
		return speed;
	}

	public void setSpeed(double speed) {
		this.speed = speed;
	}

	public float getHeight() {
		return height;
	}

	public void setHeight(float height) {
		this.height = height;
	}

	protected static int getNumberOfAnimals() {
		return numberOfAnimals;
	}

	// Since numberOfAnimals is Static you must set the value using the class name
	public void setNumberOfAnimals(int numberOfAnimals) {
		Animal.numberOfAnimals = numberOfAnimals;
	}
	
	protected static void countTo(int startingNumber){
		
		for(int i = startingNumber; i <= 100; i++){
			
			// continue is used to skip 1 iteration of the loop
			if(i == 90) continue;
			
			System.out.println(i);
			
		}
		
	}
	
	protected static String printNumbers(int maxNumbers){
		
		int i = 1;
		while(i < (maxNumbers / 2)){
			
			System.out.println(i);
			i++;
			
			// This isn't needed, but if you want to jump out of a loop use break
			if(i == (maxNumbers/2)) break;
			
		}
		
		Animal.countTo(maxNumbers/2);
		
		// You can return a value like this
		return "End of printNumbers()";
		
	}
	
	protected static void guessMyNumber(){
		
		int number;
		
		// Do while loops are used when you want to execute the code in the braces at least once
		do {
			
			System.out.println("Guess my number up to 100");
			
			// If what they entered isn't a number send a warning
			while(!userInput.hasNextInt()){
				
				String numberEntered = userInput.next();
				System.out.printf("%s is not a number\n", numberEntered);
				
			}
			number = userInput.nextInt();
			
		}while(number != 50);
		
		System.out.println("Yes the number was 50");
		
	}
	
	// This will be used to demonstrate polymorphism
	public String makeSound(){
		
		return "Grrrr";
		
	}
	
	// With polymorphism we can refer to any Animal and yet use overridden methods 
	// in the specific animal type
	public static void speakAnimal(Animal randAnimal){
		
		System.out.println("Animal says " + randAnimal.makeSound());
		
	}

	// public allows other classes to use this method
	// static means that only a class can call for this to execute 
	// void means it doesn't return a value when it finishes executing
	// This method can except Strings that can be stored in the String array args when it is executed
	
	public static void main(String[] args){
		
		Animal theDog = new Animal();
		
		System.out.println("The animal is named " + theDog.getName());
		
		System.out.println(Animal.printNumbers(100));
		
		Animal.countTo(100);
		
		Animal.guessMyNumber();
		
		// An array is a fixed series of boxes that contain multiple values of the same data type
		// How you create arrays
		// int[] favoriteNumbers;
		// favoriteNumbers = new int[20];
		
		int[] favoriteNumbers = new int[20];
		
		favoriteNumbers[0] = 100;
		
		String[] stringArray = {"Random", "Words", "Here"};
		
		// for(dataType[] varForRow : arrayName)
		for(String word : stringArray)
		{
			
			System.out.println(word);
			
		}
		
		// This is a multidimensional array
		String[][][] arrayName = { { { "000" }, { "100" }, { "200" }, { "300" } },
			     { { "010" }, { "110" }, { "210" }, { "310" } }, 
				 { { "020" }, { "120" }, { "220" }, { "320" } }};
		
		for(int i = 0; i < arrayName.length; i++)
		{
			for(int j = 0; j < arrayName[i].length; j++)
			{
				
				for(int k = 0; k < arrayName[i][j].length; k++)
				{
					System.out.print("| " + arrayName[i][j][k] + " ");
					
				}
			}
			
			System.out.println("|");
			
		}
		
		// You can copy an array (stringToCopy, indexes to copy)
		String[] cloneOfArray = Arrays.copyOf(stringArray, 3);
		
		// You can print out the whole array
		System.out.println(Arrays.toString(cloneOfArray));
		
		// Returns the index or a negative number
		System.out.println(Arrays.binarySearch(cloneOfArray, "Random"));
			
	}
		
}