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Head First (Java)




Class, Main



		// Main, void, semicolon
		// Declarations, assignments
		// For and While
		// If/else
		// Int, String, []


* Anatomy of a class

	* Main method

	In Java, everything goes in a class. You'll type your source code file (with a .java extension), then 
	compile it into a new class file (with a .class extension). When you run your program, you're really 
	running a class.
	
	The main() method is where your program starts running.

	%java

		// Project: TestingApp
		// Package: testingapp
		// File: TestingApp.java
			
		package testingapp;

		public class TestingApp {
		    public static void main(String[] args) {
			System.out.println("Hello World!");
		    }
		} // Output: Hello World!


	* Void:
		The return type (void) means there's no return value.


	* Semicolon:
		Every statement must end in semicolon.


* Statements
	
	Declaratlons, assignments, method calls, etc:

	%java 

	    public static void main(String[] args) {

		int x = 3;
		String name = "Catalin";
		x = x*3;
		System.out.println("x is " + x);
		    // this is a comment
		    // Output: x is 9
	    }


* Loops

	For and While
	
	%java

	    public static void main(String[] args) {
		
		int x = 3;
		while (x < 10) {
		    x++;
		    System.out.println("x: " + x);
		}
		
		for(int i=0; i<10; i++) {
		    System.out.println("i: " + i);
		}
	    }


* Branching
	
	If/else tests

	%java

	    public static void main(String[] args) {
		
		int x = 3;
		if (x == 0) {
		    System.out.println("x is 0");
		} else {
		    System.out.println("x isn't 0");
		}
	    }


* Int, String, List (array)

	%java

	    // Get random entry from a set
	
	    public static void main(String[] args) {
		
		int x = 1;
		String a = "a";
		String[] listOne = {"a1", "b2", "c3"};
		
		int oneLength = listOne.length;
		
		int rand1 = (int) (Math.random() * oneLength);
		
		System.out.println("Random word is " + listOne[rand1]);
	    }