class Test {
 void display() {
  System.out.print("\"Hello World!\"");
 }
 public static void main(String[] a) 
 {
  Test t = new Test();
  t.display();
 }
}

"Hello World!"

import java.util.Scanner;
class Employee {
 int empID,deptID,salary;
 String empName,bloodGroup;
 void setEmployeeDetail() {
  Scanner s=new Scanner(System.in);
  System.out.print("Enter empId: ");
  empID=Integer.parseInt(s.nextLine());
  System.out.print("Enter Name: ");
  empName = s.nextLine();
  System.out.print("Enter Dept. Id: ");
  deptID=Integer.parseInt(s.nextLine());
  System.out.print("Enter Blood Group: ");
  bloodGroup= s.nextLine();
  System.out.print("Enter Salary: ");
  salary=Integer.parseInt(s.nextLine());
 }
 void printEmployeeDetails() {
  System.out.println("EMP. ID - "+empID+
          "\nEMP NAME - "+empName+
           "\nDEPT ID - "+deptID+
          "\nBLOOD GROUP - "+bloodGroup+
          "\nSALARY - "+salary);
 }
 public static void main(String[] a)
 {
  Employee e = new Employee();
  e.setEmployeeDetail();
  e.printEmployeeDetails();
 }
}

Enter empId: 12
Enter Name: Alok
Enter Dept. Id: 5
Enter Blood Group: A
Enter Salary: 30000
EMP. ID - 12
EMP NAME - Alok
DEPT ID - 5
BLOOD GROUP - A
SALARY - 30000

class Temp {
 float convert(int c) {
  float f = (float)9.0/5*c;
  return f+32;
 }
 public static void main(String[] a)
 {
  Temp t = new Temp();
  System.out.println("Celc.\tFahren.");
  for(int i=1; i<=10; i++) {
   float x = t.convert(i);
   System.out.println(i+"\t"+x);
  }
 }
} 

Celc.   Fahren.
1       33.8
2       35.6
3       37.4
4       39.2
5       41.0
6       42.8
7       44.6
8       46.4
9       48.199997
10      50.0

import java.util.Scanner;
class Area {
 final double PI = 3.14;
 void areaOfCircle(int r) {
  double ar = PI*r*r;
  System.out.println("Circle Area= "+ar);
 }
 void areaOfCylinder(int r, int h) {
  double ar = 2*PI*r*h;
  System.out.print("Cylinder Area= "+ar);
 }
 public static void main(String[] a)
 {
  Area ar = new Area();
  Scanner s=new Scanner(System.in);
  System.out.print("Enter Circle Radius: ");
  int r = s.nextInt();
  System.out.print("Enter Cylinder Radius: ");
  int r2 = s.nextInt();
  System.out.print("Enter Cylinder Height: ");
  int h = s.nextInt();
  ar.areaOfCircle(r);
  ar.areaOfCylinder(r2,h);
 }
}  

Enter Circle Radius: 7
Enter Cylinder Radius: 7
Enter Cylinder Height: 10
Circle Area= 153.86
Cylinder Area= 439.6

import java.util.Scanner;
class Test {
 public int factorial(int x) {
  int f = 1;
  for(int i = 1; i<=x; i++) {
   f = f*i;
  }
  return f;
 }
}
class Demo {
 public static void main(String[] a)
 {
  Test t = new Test();
  Scanner s=new Scanner(System.in);
  System.out.print("Enter a Num: ");
  int x = s.nextInt();
  int fact = t.factorial(x);
  System.out.print("Result = "+fact);
 }
}

Enter a Num: 6
Result = 720

import java.util.Scanner;
class Test {
 public static float fact(int x) {
  int f = 1;
  for(int i = 1; i<=x; i++) {
   f = f*i;
  }
  return f;
 }
 public static void main(String[] a)
 {
  Scanner s=new Scanner(System.in);
  System.out.print("Enter N: ");
  int n = s.nextInt();
  System.out.print("Enter R: ");
  int r = s.nextInt();
  float res=fact(n)/(fact(n-r)*fact(r));
  System.out.print("Result = "+res);
 }
}

Enter N: 5
Enter R: 3
Result = 10.0 

class Rectangle { 
 int l, b;
 Rectangle() {
  l = 5;
  b = 3;
 }
 Rectangle(int l, int b) {
  
  this.l = l;
  this.b = b;
 }
 void area() {
  System.out.println("Area- "+(l*b));
 }
}
class Main {
 public static void main(String[] a)
 {
  Rectangle r =new Rectangle();
  r.area();
  Rectangle r2 = new Rectangle(20,10);
  r2.area();
 }
}

Area- 15
Area- 200

import java.util.Scanner;
class Test {
 int x;
 Test(int num){
  x = num ;
 }
 int getReverse() {
  int temp, rev =0;
  while(x != 0) {
   temp = x%10;
   rev = rev *10+temp;
   x = x/10;
  }
  return rev;
 }
 public static void main(String[] a)
 {
  Scanner s=new Scanner(System.in);
  System.out.print("Enter Num: ");
  int x = s.nextInt();
  Test t = new Test(x);
  int res = t.getReverse();
  System.out.print("Reverse = "+res);
 }
}

Enter Num: 15465
Reverse = 56451

class Demo {
 int a;
 Demo(int a) {
  this.a = a;
 }
}
class Test {
 int x = 20;
 void square(Demo d) {
 d.a = d.a*d.a;
 }
}
class Main{
 public static void main(String[] a)
 {
  Demo d = new Demo(10);
  Test t = new Test();
  System.out.println("Before Call- "+d.a);
  t.square(d);
  System.out.print("After Call- "+d.a);
 }
}

Before Call- 10
After Call- 100 

class Test {
 int a = 5;
 static int b = 5;
 void display() {
  a++;
  b++;
  System.out.println("A = "+a);
  System.out.println("B = "+b);
 }
 public static void main(String[] a)
 {
  Test t = new Test();
  t.display();
  Test t2 = new Test();
  t2.display();
  Test t3 = new Test();
  t3.display();
 }
}

A = 6
B = 6
A = 6
B = 7
A = 6
B = 8

class Counter {
 static int count = 0;
 void counter(){
  count++;
 }
 void display() {
  System.out.println("Total time- "+count);
 }
 public static void main(String[] a)
 {
  Counter c = new Counter();
  c.counter();
  c.counter();
  Counter c2 = new Counter();
  c2.counter();
  c2.counter();
  c2.display();
 }
}

Total time-4