Example

Java Tutorial for Beginners | Crash Course
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public class Exams
{
    public static void main(String[] args)
    {
      System.out.println("Hello World");
    }
}
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Source file > Compiler > Bitecode > JVM
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public class VariableDemo 
{
	public static void main(String args[])
	{
//		int,float, double
		
		long l = 5000000000l;  // 8 bytes
		int i = 5;            // 4 bytes -> 32 bits
		short s = 5;         // 2 bytes -> 16 bits -> -32768 to 32767
		byte b = 5;         // 1 byte -> 8 bits -> -128 to 127
		float f = 5.5f;
		double d = 5.5;
		
		char c ='A';
		c = 66;  // American Standard code for information interchange
		
		System.out.println(c);
		
		double d1 = 5;    // implicit conversion
		int k =(int)5.6; // type casting
		System.out.println(k);
		
	}
}


Byte> Shorrt & Char > Int > long > float > Double
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Naming Convetion

Class -->  noun (ex: Exam, MyFirstJavaClass(Camle casing Rule))
Mthod --> Verb (ex:copy)
Variable --> (ex: id)
Constent --> (ex: PI, MAX_PRICE)
Constructor --> Exam() (No parameters in the brackets)

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public class OperatorDemo {
	
  /*
   * 
   *  Arithmetic +,-,*,/,%
   *  Bitwise
   *  Relational
   *  Logical
   * 
   */
	
	public static void main(String args[])
	{
		int m=6,n=4;
		int r1 = m+n;   // 8
		int r2 = m-n;   // 4
		int r3 = m*n;   // 12
		double r4 = (double)m/n;   // 3
		
		int r5 = m%n;
		
		System.out.println(r1);
		System.out.println(r2);
		System.out.println(r3);
		System.out.println(r4);
		System.out.println(r5);
	}

}
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public class OperatorDemo {
	

	public static void main(String args[])
	{

		int m = 4;
		int n = 5;
		
//		n += m; // n = n+m
//		n++;   // n = n+1
//	
//		++n; // pre increment
//		n++; // post increment
		
		m = ++n;
		
		System.out.println(m);
		System.out.println(n);
	}
}
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public class SelectionDemo 
{
    public static void main(String args[])
    {

        int n = 5;

        if(n==0)
        {
            System.out.print("nothing");
            System.out.print("Bye");
        }
        else if(n%2==0)
        {
            System.out.print("Even");
        }
        else
        {
            System.out.print("Odd");
        }

    }
}
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public class SelectionDemo 
{
	// ternary operator
		
	public static void main(String args[])
	{
		int i = 5;		
		int j = 0;
	
//		if(i>6)
//			j=1;
//		else
//			j=2;
	
		j = i>6?1:2;		// ?: -> condition?expr1:expr2
		
		System.out.println(j);
	}
}

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public class SelectionDemo 
{
// Switch Statement
	
	public static void main(String args[])
	{
		
		int n = 6;
		
		switch(n)
		{
		case 1:
			System.out.println("One");
			break;
		case 2:
			System.out.println("Two");
			break;
		case 3:
			System.out.println("Three");
			break;
		case 4:
			System.out.println("Four");
			break;
		case 5:
			System.out.println("Five");
			break;
		default:
			System.out.println("No Match");
		}
	}
}

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public class SelectionDemo 
{
// Can use sting in Switch Statement for jave version more than 1.7
	
	public static void main(String args[])
	{
		String d = "abc";
		
		switch(d)
		{
		case "abc":
			System.out.println("One");
			break;
	    case "pqr":
	    	System.out.println("Two");
	    	break;
	    	
	    default:
	    	System.out.println("No Match");
		}

    }
}
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public class iterationDemo 
{
	public static void main(String args[])
	{
//while loop		
		int i=1;
		while(i<=5)
		{
			System.out.println("Hello");
			i++;
		}
	}
}	

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public class iterationDemo 
{
	public static void main(String args[])
	{
		
//do while loop
		
		int i=9;
		do
		{
			System.out.println("Hello");
			i++;
		}while(i<=5);
	}

}
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public class iterationDemo 
{
	public static void main(String args[])
	{
		
//for loop
		
		for(int i=1;i<=5;i++)
		{
			System.out.println("Hello");
		}
	}
}

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public class iterationDemo 
{
	//Nested for
	
		public static void main(String args[])
		{
			for(int i=1;i<=4;i++)
			{
				for(int j=1;j<=4;j++)
				{
					System.out.print("* ");
				}
				System.out.println();
		    }

		}
		
}

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public class iterationDemo 
{
	//Nested for
	
		public static void main(String args[])
		{
			for(int i=1;i<=4;i++)
			{
				for(int j=1;j<=4;j++)
				{
					System.out.print(j + " ");
				}
				System.out.println();
		    }
	     }
}
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Answer for assignment would be

class Pattern
{
    public static void main (String Args[])
    {
        for(int i=0; i<=3; i++)
        {           
            for(; i>=1 && i<=2; i++)
            {
                System.out.println("$     $");
            }
            System.out.println("$ $ $ $");
        }
    }
}

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public class JumpDemo 
{

	public static void main(String[] args)
	{
//Continue
		for(int i=1;i<=10;i++)
			if(i==7) 
			{
				continue;
			}
			System.out.println("value is " + i);

	}
}

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public class JumpDemo 
{

	public static void main(String[] args)
	{			
//Break
	for(int i=1;i<=10;i++)
	{
		if(i>5) 
		{
			break;
		}
		System.out.println("value is " +  i);
	}
}
}
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class Calc
{
	int num1;
	int num2;
	int result;
	
    public void perform()
	{
		result = num1 + num2;
	}
}

public class ObjectDemo 
{
	public static void main(String[] args)
	{
		Calc obj = new Calc(); //knows something and does somthing
		obj.num1 = 3;
		obj.num2 = 5;
		
		obj.perform();
		
		System.out.println(obj.result);
	}
}

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class Calc
{
	int num1;
	int num2;
	int result;
	
	public Calc()
	{
		num1 = 5;
		num2 = 5;
		System.out.println("in constructor");
	}
	public Calc(int n)
	{
		num1 = n;
		num2 = n;
	}
	public Calc(double d,int n)
	{
		num1 = (int) d;
		num2 = n;
	}
	
}

public class ObjectDemo 
{
	public static void main(String[] args)
	{
		Calc obj = new Calc(9.5,8); //Constructor
		
		System.out.println(obj.num1);

	}
}

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class Calc
{
    int num1;
    int num2;		// Instance Variables
    int result;		

    public Calc(int num1,int num2)
    {
        this.num1 = num1; // Local Variables
        this.num2 = num2; //This represents current object
    }

}

public class Exams
{
    public static void main(String[] args)
    {
        Calc obj = new Calc(4,5); //Constructor

        System.out.println(obj.num1);
        System.out.println(obj.num2);

    }
}
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class Casio
{
	int num1;
	int num2;
	String operation;

	
	public void add(int i , int j) 
	{
		System.out.println(i + j);
	}
	public void add(int i , int j , int k) 
	{
		System.out.println(i + j + k);
	}
	public void add(double i, double j) 
	{
		System.out.println(i + j);
	}
}


public class MethodOverloadingDemo 
{
	public static void main(String[] args)
	{

		obj.add(5, 2);
		
		obj.add(4, 3,5);
		
		obj.add(4.5, 3.8);
	}

}

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class Casio
{
	int num1;
	int num2;
	String operation;
	
	public Casio()
	{
		num1 = 0;
		num2 = 0;
		operation = "Nothing";
	}
	public Casio(int i)
	{
		num1 = i;
		num2 = 0;
		operation = "Nothing";
	}
	public Casio(int i,int j,String op)
	{
		num1 = i;
		num2 = j;
		operation = op;
	}
}
	


public class MethodOverloadingDemo 
{
	public static void main(String[] args)
	{
		Casio obj = new Casio(4,5,"Add");	
	}

}

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class Emp
{
	int eid;
	int salary;
	static String ceo;

	public Emp()  // when you create an object
	{
		eid = 1;
		salary = 3000;
		System.out.println("in constructor");
	}

	public void show()
	{
		System.out.println(eid + " : " + salary + " : " + ceo);
	}
}

public class StaticDemo
{

	public static void main(String[] args)
	{
		
		Emp navin = new Emp();
		navin.eid = 8;
		navin.salary = 4000;
		Emp.ceo = "Mahesh";
	
		Emp rahul = new Emp();
		rahul.eid = 9;
		rahul.salary = 5000;
		Emp.ceo = "Mahesh";   // we dont need object but the class name
		
		Emp.ceo = "Nikita";		// It over rides ceo for Naveen too
		
		navin.show();
		rahul.show();
	}

}
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class Emp
{
	int eid;
	int salary;
	static String ceo;

	static    // when you load a class
	{
		ceo = "Larry";
		System.out.println("in static");		//Static Block gets executed only when class is loaded and it's only once
	}
	
	public Emp()  // when you create an object
	{
		eid = 1;
		salary = 3000;
		System.out.println("in constructor");	//Sequence of Static block doesn't matter, unless there are more than one static block
	}
	
	public void show()
	{
		System.out.println(eid + " : " + salary + " : " + ceo);
	}
}

public class StaticDemo
{
	static int i = 0;
	public static void main(String[] args)	// Class loads first>Method Loads second>variables in method loads third
	{
		i = 9;								// Variable can not be called inside static method unless it is a static variable
		
		Emp navin = new Emp();

		Emp rahul = new Emp();
		
		navin.show();
		rahul.show();
	}

}
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