Cheat Sheet for Java

MyClass.java

//Single line comment
/* multiple
*  line
*  comment
*/

//import libraries
import java.util.Scanner;
import java.math.BigDecimal;

// A class defines the attributes (fields) and capabilities (methods) of an object
public class MyClass{ //public is accessible by everyone  

/* static means that this number is going to be shared by every MyClass object that is created
*  final means that this is a constant, final classes cannot be subclassed
*  final means that this value cannot be changed
*  final methods cannot be overwritten */
  public static final double FAVNUMBER = 1.45; //common to use all capitals for final classes
  
  // variables(aka fields) can start with a letter, and underscore_ or a dollar sign $
  // private can only be accessed by other methods in its containing class
  // common practice to make all variables private to secure code
  
  /* Primitive data types in java
  *  String, int, boolean, byte, long, char, double, float */
  // 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 
	// code contained within the src code folder is the same package
	protected static int myNumber = 0; 
	
	static Scanner userInput = new Scanner(System.in);
	
	// Any time an MyClass object is created this function called the constructor is called
	// to initialize the object
	public MyClass(){
		// Shorthand for myTotalNumber = myTotalNumber + 1;
		myTotalNumber++;
		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 myString: \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.setmyString(userInput.nextLine());
			// hasNextInt, hasNextFloat, hasNextDouble, hasNextBoolean, hasNextByte,
			// hasNextLong, nextInt, nextDouble, nextFloat, nextBoolean, etc.
		}
		this.setmyChar();
		this.setmyLong();
	} //end public MyClass
}; //end class MyClass