Java code exsamples Cheat Sheet (DRAFT) by NoxLupus

public class FirstJavaProgram {
  public static void main(String[] args){
    System.out.println("This is my first program in java");
  }//End of main
}//End of FirstJavaProgram Class

public class ArithmeticOperatorDemo {
   public static void main(String args[]) {
      int num1 = 100;
      int num2 = 20;

      System.out.println("num1 + num2: " + (num1 + num2) );
      System.out.println("num1 - num2: " + (num1 - num2) );
      System.out.println("num1  num2: " + (num1  num2) ); 
      System.out.println("num1 / num2: " + (num1 / num2) );
      System.out.println("num1 % num2: " + (num1 % num2) );

      System.out.println("5.0 % 10.0: " + (5.0 % 10.0) );
      System.out.println("num1 + num2: " + num1 + num2 );
   }
}

//abstract class
abstract class Sum{
   // Two abstract methods
   public abstract int sumOfTwo(int n1, int n2);
   public abstract int sumOfThree(int n1, int n2, int n3);
	
   //Regular method 
   public void disp(){
	System.out.println("Method of class Sum");
   }
}

//Parent class or Superclass or base class
class Superclass
{
   int num = 100;
}
//Child class or subclass or derived class
class Subclass extends Superclass
{
   //The same variable num is declared in the Subclass

    int num = 110;
    void printNumber(){
	System.out.println(num);
        System.out.println(super.num);
    }
        public static void main(String args[]){
	Subclass obj= new Subclass();
	obj.printNumber();	
    }
}

Class X
{
   public void methodX()
   {
     System.out.println("Class X method");
   }
}

Class Y extends X
{
public void methodY()
{
System.out.println("class Y method");
}
}

Class Z extends Y
{
   public void methodZ()
   {
     System.out.println("class Z method");
   }
   public static void main(String args[])
   {
     Z obj = new Z();
     obj.methodX(); //calling grand parent class method
     obj.methodY(); //calling parent class method
     obj.methodZ(); //calling local method
  }
}

public class IfStatementExample {
public static void main(String args[]){
      int num=70;
      if( num < 100 ) {
	  System.out.println("number is less than 100");
      }else {
           System.out.println("number is more less than 100");
      }
   }
}

public class Test {

   public static void main(String args[]) {
      int x = 10;

      while( x < 20 ) {
         System.out.print("value of x : " + x );
         x++;
      }
   }
}

public class Test {

   public static void main(String args[]) {
      int x = 20;

      do {
         System.out.print("value of x : " + x );
         x++;
         System.out.print("\n");
      }while( x < 20 );
   }
}

class ForLoopExample {
    public static void main(String args[]){
         for(int i=10; i>1; i--){
              System.out.println("The value of i is: "+i);
         }
    }
}

public class Test {

   public static void main(String args[]) {
      // char grade = args[0].charAt(0);
      char grade = 'C';

      switch(grade) {
         case 'A' :
            System.out.println("Excellent!"); 
            break;
         case 'B' :
         case 'C' :
            System.out.println("Well done");
            break;
         case 'D' :
            System.out.println("You passed");
         case 'F' :
            System.out.println("Better try again");
            break;
         default :
            System.out.println("Invalid grade");
      }
      System.out.println("Your grade is " + grade);
   }
}

public class TestArray {

   public static void main(String[] args) {
      double[] myList = {1.9, 2.9, 3.4, 3.5};

      // Print all the array elements
      for (int i = 0; i < myList.length; i++) {
         System.out.println(myList[i] + " ");
      }
     
      // Summing all elements
      double total = 0;
      for (int i = 0; i < myList.length; i++) {
         total += myList[i];
      }
      System.out.println("Total is " + total);
      
      // Finding the largest element
      double max = myList[0];
      for (int i = 1; i < myList.length; i++) {
         if (myList[i] > max) max = myList[i];
      }
      System.out.println("Max is " + max);  
   }
}

Condition 1: (x < y && x > 0)		false
Condition 2: (a != d || x != 5)			true
Condition 3: !(true && false)			true
Condition 4: (x > y || a == 'A' || d != 'A')	true
for x = 5, y = 3, and a and d are char variables with a = 'a' and d = 'A'
-----------------------------------------------------------------------------------------------------
if (score >= 90) 
     grade = 'A';
if (score >= 80) 
     grade = 'B';
if (score >= 70) 
     grade = 'C';
if (score >= 60) 
     grade = 'D';
else       
     grade = 'F'; 
//will work correctly only if score < 70, because it dosent brake. a A is also a C,D
-----------------------------------------------------------------------------------------------------
if (x > 0) 
     x++;
else  
     if (x < 0) 
          x--; 
//adds one if x is pos and subs on if x is neg
-----------------------------------------------------------------------------------------------------
if (count != 0 && total / count > max) 
                 max = total / count;
//count = 0, The condition short circuits and the assignment statement is not executed nor dose it get to divitoin by 0
-----------------------------------------------------------------------------------------------------
if (x < 0) 
     y = x; 
else 
     y = 0;
// or
y = (x < 0) ? x : 0;
-----------------------------------------------------------------------------------------------------
//Start: X = 1 end: x = 128, but if x = 0 it is an infinite lop
while (x < 100)
      x *= 2;
-----------------------------------------------------------------------------------------------------
//will execute 10 times:
int x = 10;
while (x > 0)
{
     System.out.println(x);
     x--;
}
-----------------------------------------------------------------------------------------------------
//end: x = 10: 1+2+3+4
for (int i=0; i<5; i++)
      x += i;
-----------------------------------------------------------------------------------------------------
int x = 10;
do {
     System.out.println(x);
     x--;
} while (x > 0);
//executes 1 time
-----------------------------------------------------------------------------------------------------
for (int j = 0; j < 1000; ) X++; 
//is a infinite loop
-----------------------------------------------------------------------------------------------------
for (int j = s.length( ); j > 0; j--)
     System.out.print(s.charAt(j-1));
//it prints s out backwards with the last character
-----------------------------------------------------------------------------------------------------
int[ ] arr = new int[5]; 
arr.length = 5
int[ ] list = {5, 10, 15, 20, 6};
-----------------------------------------------------------------------------------------------------
BankAccount[ ] firstEmpireBank;
firstEmpireBank = new BankAccount[1000];
//will creat 1,000 reference variables, each of which could point to a BankAccount object
-----------------------------------------------------------------------------------------------------

 int numberOfDays; 
 byte nextInStream;
 short hour;
 long totalNumberOfStars;
 float reactionTime;
 double itemPrice;

class XYZ{  
   final void demo(){
      System.out.println("XYZ HI");
   }  
}  
	     
class ABC extends XYZ{  
   void demo(){
      System.out.println("ABC HI");
   }  /* this method can not be crreated since the parnts method of the sasm name is final. howver we can just let it get inherited down.*/ 

   public static void main(String args[]){  
      ABC obj= new ABC();  
      obj.demo();  
   }  
}
------------------------------------
package abcpackage;

public class Addition {

   public int addTwoNumbers(int a, int b){
	return a+b;
   }
}

package xyzpackage;
import abcpackage.*;
class Test{
   public static void main(String args[]){
      Addition obj = new Addition();
      System.out.println(obj.addTwoNumbers(100, 1));
   }
}

BeginnersBook obj1 = new BeginnersBook();
BeginnersBook obj2 = new BeginnersBook();
obj2 = obj1;

char[] sayhello = { 'h', 'e', 'l', 'l', 'o'};
String str = new String(sayhello);
str = null;

class EncapsulationDemo{
private String empName;
 public String getEmpName(){
        return empName;
    }
 public void setEmpName(String newValue){
        empName = newValue;
    }
}

public class EncapsTest{ // this class can not see empName
    public static void main(String args[]){
         EncapsulationDemo obj = new EncapsulationDemo();
         obj.setEmpName("Mario");
         System.out.println("Employee Name: " + obj.getEmpName());
    } 
}

DecimalFormat
void applyPattern(String pattern)
String format(Double number)

//**
//  Purchase.java       Author: Lewis/Loftus
//
//  Demonstrates the use of the NumberFormat class to format output.
//**

import java.util.Scanner;
import java.text.NumberFormat;

public class Purchase
{
   //-----------------------------------------------------------------
   //  Calculates the final price of a purchased item using values
   //  entered by the user.
   //-----------------------------------------------------------------
   public static void main (String[] args)
   {
      final double TAX_RATE = 0.06;  // 6% sales tax

      int quantity;
      double subtotal, tax, totalCost, unitPrice;

      Scanner scan = new Scanner (System.in);

      NumberFormat fmt1 = NumberFormat.getCurrencyInstance();
      NumberFormat fmt2 = NumberFormat.getPercentInstance();

      System.out.print ("Enter the quantity: ");
      quantity = scan.nextInt();

      System.out.print ("Enter the unit price: ");
      unitPrice = scan.nextDouble();

      subtotal = quantity * unitPrice;
      tax = subtotal * TAX_RATE;
      totalCost = subtotal + tax;

      // Print output with appropriate formatting
      System.out.println ("Total: " + fmt1.format(totalCost));
   }
}

random()
float nextFloat()
int nextInt()
int nextInt(int num)

public enum Directions{
	  EAST, 
	  WEST, 
	  NORTH, 
	  SOUTH
}  

 public static void main(String[] args) {
        EnumDemo obj1 = new EnumDemo(Directions.EAST);
        obj1.getMyDirection();
        Directions.ch­arA­t(2)
    }
}

public class Example{  
   public static void main(String args[]){ 
 
	//creating a string by java string literal 
	String str = "Beginnersbook"; 
	char arrch[]={'h','e','l','l','o'}; 

	//converting char array arrch[] to string str2
	String str2 = new String(arrch); 
		
	//Displaying all the three strings
	System.out.println(str);  
	System.out.println(str2);  
   }
}

class Example2
{
      private int var;
      //default constructor
      public Example2()
      {
             this.var = 10;
      }
      //parameterized constructor
      public Example2(int num)
      {
             this.var = num;
      }

public static void main(String args[])
      {
    Example2 obj = new Example2();
    Example2 obj2 = new Example2(100);
    System.out.println("var is: "+obj.getValue());
    System.out.println("var is: "+obj2.getValue());
      }
}

class JavaExample{
  static int i = 100;
  static String s = "Beginnersbook";
  //Static method
  static void display()
  {
     System.out.println("i:"+i);
     System.out.println("i:"+s);
  }

  //non-static method
  void funcn()
  {
      //Static method called in non-static method
      display();
  }
  //static method
  public static void main(String args[])
  {
	  JavaExample obj = new JavaExample();
	  //You need to have object to call this non-static method
	  obj.funcn();
	  
      //Static method called in another static method
      display();
   }
}

integer(int value)
prim typeValue()
// dyte byteValue() retuns number in primative data
static int parseInt(String str)
staic String toBinary{hex, Octal}String(int num)

String format(double number)
static NumberFormat getCurrencyInstamce()
static NumberFormat getPercenctInstamce()

//creates obj
// then do obj.format(Foo)