public class Demo 
{
	int id=101;
	String name="TechKnow";
	public static void main(String[] args) 
	{
		Demo obj=new Demo();//obj is instance of Demo class
		System.out.println("id"+" "+obj.id);
		System.out.println("name"+" "+obj.name);
	}

}

id 101
name TechKnow

class Student
{
	int rollno;
	String name;
	int m1 , m2 , m3;
	int tot;
	float per;
	String grade;
	void input(int rollno , String name, int m1 , int  m2 , int m3)
	{
		this.rollno = rollno;
		this.name = name;
		this.m1 = m1;
		this.m2 = m2;
		this.m3= m3;
	}
	void cal()
	{
		tot = m1+ m2 + m3;
		per = tot/3;
		if(per>90)
		grade= "A";
		else
		grade="B";
	}
	void print()
	{
		System.out.println("** Student Report Card **");
		System.out.println("Rollno "+rollno);
		System.out.println("Name "+name);
		System.out.println("Marks1 "+m1);
		System.out.println("Marks2 "+m2);
		System.out.println("Marks3 "+m3);
		System.out.println("Total "+tot);
		System.out.println("Per "+per);
		System.out.println("Grade "+grade);	
	}
	public static void main(String args[])
	{
		Student obj = new Student();
		obj.input(1001, "Ram",90, 89 , 78);
		obj.cal();
		obj.print();
	}
}

** Student Report Card **
Rollno 1001
Name Ram
Marks1 90
Marks2 89
Marks3 78
Total 257
Per 85.0
Grade B

class Emp
{
	int empno; // Instance variable
	String name;
	float sal;
	Emp()  // This is Default Cons, Constructor Call Automatically 
	       //It intialize the instance Var
	{
		System.out.println("This is Default Cons ");
		empno = 1001;
		name = "Ram";
		sal = 9090.0f;
	}
	Emp(int empno , String name , float sal)
	{
		this.empno = empno;
		this.name = name;
		this.sal = sal;
	}
	public void print()
	{
		System.out.println("Empno "+empno +" Name "+ name +" Sal "+sal);
	}
	public static void main(String agrs[])
	{
		Emp e = new Emp();
		e.print();
		Emp e1 = new Emp(1002,"Shyam", 8883.3f);
		e1.print();
	}
}

This is Instance Variable
Empno 1001 Name Ram Sal 9090.0
Empno 1002 Name Shyam Sal 8883.3

public class Demo
{
	int num;
	Demo()
	{
		num++;
	}
	public static void main(String[] args)
	{
		Demo d1 = new Demo();
		System.out.println("No. of instances  for d1  : "+ d1.num);
		Demo d2 = new Demo();
		System.out.println("No. of instances  for d1  : "+ d1.num);
		System.out.println("No. of instances  for d2  : "+ d2.num);
		Demo d3 = new Demo();
		System.out.println("No. of instances  for d1  : "+ d1.num);
		System.out.println("No. of instances  for d2  : "+ d2.num);
		System.out.println("No. of instances  for d3  : "+ d3.num);
	}
}

No. of instances  for d1  : 1
No. of instances  for d1  : 1
No. of instances  for d2  : 1
No. of instances  for d1  : 1
No. of instances  for d2  : 1
No. of instances  for d3  : 1

class Demo 
{
	int length = 10;
	int breadth = 10;
	int height = 10;
	public static int num = 0; // static variable
	public static int NoOfCubes()  //static method
	{
		return num;
	}
	public Demo() 
	{
		num++;
	}
	public static void main(String args[]) 
	{
		System.out.println("Number of Cube objects = " + Demo.num);
		System.out.println("Number of Cube objects = "+ Demo.NoOfCubes());
	}	
}

Number of Cube objects = 0
Number of Cube objects = 0

class Check
{
	void display(String name,int id)//Instance Method
	{
		System.out.println("Name"+" "+name);
		System.out.println("Id"+" "+id);
	}
	public static void main(String args[])
	{
		Check cc=new Demo();
		cc.display("Techknow",101);
	}
}

Name Techknow
Id 101

class Demo
{
	static int id;
	void display()
	{
		System.out.println("id="+id);
		id++;
	}
	void display1()
	{
		System.out.println("id="+id);
		id++;
	}
	void display2()
	{
		System.out.println("id="+id);
		id++;
	}
	public static void main(String args[])
	{
		Demo d1=new Demo();
		d1.display();
		d1.display1();
		d1.display2();
	}
}

id=0
id=1
id=2

package com.encapsule;
public class Demo 
{
	private String name;
	private String idNum;
	private int age;
	
	public int getAge()
	{
		return age;
	}
	
	public String getName()
	{
		return name;
	}
	
	public String getIdNum()
	{
		return idNum;
	}
	
	public void setAge( int newAge)
	{
		age = newAge;
	}
	
	public void setName(String newName)
	{
		name = newName;
	}
	
	public void setIdNum( String newId)
	{
		idNum = newId;
	}
}

Name : Shivank
Age : 23

package inherit;
class  Person
{
	String name;
	int age;
	public void input(String name, int age)
	{
		this.name=name;
		this.age=age;
	}
	public void show()
	{
		System.out.println("Calling from Person");
		System.out.println("NAME : "+name);
		System.out.println("AGE : "+age);
	}
}
class Student extends Person
{
	String standard;
	float m1,m2,m3,total,percentage;
	int stdno;
	public void input(String standard,float m1,float m2,float m3,int
	stdno)
	{
		this.standard=standard;
		this.m1=m1;
		this.m2=m2;
		this.m3=m3;
		this.stdno=stdno;
	}
	public void show()
	{
		System.out.println("Calling from Student");
		System.out.println("standard : "+standard);
		System.out.println("marks in physics :"+m1);
		System.out.println("marks in chemistry :"+m2);
		System.out.println("marks in  maths :"+m3);
		System.out.println("Student number :"+stdno);
		System.out.println("total marks :"+total);
		System.out.println("percentage marks :"+percentage);
	}
	public void marks()
	{
		total=m1+m2+m3;
		percentage=total*100/300.0f;
	}
}
class Employee extends Student
{
	int empno;
	float salary;
	float hra,gs;
	public void input(int empno,float salary)
	{
	    this.empno=empno;
	    this.salary=salary;
	}
	public void show()
	{
		System.out.println("Calling from Employee");
		System.out.println("EMPLOYEE NUMBER : "+empno);
		System.out.println("salary : "+salary);
		System.out.println("HRA : "+hra);
		System.out.println("GS : "+gs);
	}
	public void calculate()
	{
		hra=  0.3f*salary;
		gs=salary+hra;
	}
}

package inherit;
class Inheritance
{
   public static void main(String args[])
   {
       Person p=new Person();
       p.input("abhishek",22);
       p.show();
       p=new Student();
       Student s= new Student();
       s.input("btech",90,92,93,06);
       s.marks();
       p.show();
       s.show();
       p=new Employee();
       Employee e= new Employee();
       e.input(5751, 80000);
       e.calculate();
       e.show();
       s.show();
       p.show();
   }
}

Calling from Person
NAME : abhishek
AGE : 22
Calling from Student
standard : null
marks in physics :0.0
marks in chemistry :0.0
marks in  maths :0.0
Student number :0
total marks :0.0
percentage marks :0.0
Calling from Student
standard : btech
marks in physics :90.0
marks in chemistry :92.0
marks in  maths :93.0
Student number :6
total marks :275.0
percentage marks :91.666664
Calling from Employee
EMPLOYEE NUMBER : 5751
salary : 80000.0
HRA : 24000.0
GS : 104000.0
Calling from Student
standard : btech
marks in physics :90.0
marks in chemistry :92.0
marks in  maths :93.0
Student number :6
total marks :275.0
percentage marks :91.666664
Calling from Employee
EMPLOYEE NUMBER : 0
salary : 0.0
HRA : 0.0
GS : 0.0

public  class Test
{
	public void add(int i, int j)
    {
		System.out.println(i + j);
	}
	public void add(String p,String r)
	{
		System.out.println(p  + r);
	}
	public void add( char a, char b)
	{
		System.out.println(a + b);
	}
	public static void main(String [] args)
	{
		Test ol = new Test();
		ol.add(15,20);
		ol.add("Tech", "know");
		ol.add('g','h');
	}
}

35
Techknow
207

class Animal
{
	public void move()
	{
		System.out.println("Animals can move");
	}	
}

class Dog extends Animal
{
	public void move()
	{
		System.out.println("Dogs can walk and run");
	}
}

public class Test
{
	public static void main(String args[])
	{
		Animal a = new Animal(); // Animal reference and object
		Animal b = new Dog(); // Animal reference but Dog object
		a.move();// runs the method in Animal class
		b.move();//Runs the method in Dog class
	}
}

Animals can move
Dogs can walk and run