How to use class in java program

//class 
class student
{
String name;
int roll_no;
}
//main class
class ans
{
//main function
public static void main(String args[])
{
//object declaration
student s = new student();
s.name = "John";
s.roll_no = 18;
//print function
System.out.println("Name is" +s.name+ "and roll number is" +s.roll_no);
}
}

Output : Name is John and roll number is 18.

Use of For Loop in Java Programming

// main class 

class multiple{// void functionpublic static void main(String[] args){

// variable declaration

int a,b,c;

a=20;

// For loop

for(b=1; b<=10;b++)

{

// multiple operator

c=a*b;

//output printing function on screen

System.out.println("a*b="+c);

}

}

}

output : 20;

             40;

             60;

             80;

             100;

             120;

             140;

             160;

             180;

             200;

How to use of Operator in java

// main class
public class second
{
// main function
public static void main(String args[])
{
//variable declaration
int a,b,c,d,e,f;
a=30;
b=20;
// operator use 
c=a*b;
d=a+b;
e=a-b;
f=a/b;
// print function
System.out.println("a*b="+c);
System.out.println("a+b="+d);
System.out.println("a-b="+e);
System.out.println("a/b="+f);
}
}

output : a*b : 600;
             a+b : 50;
             a-b :  10;
             a/b :   1.5;

Swap two number using third variable.

// main class
public class swap
{
// void main function
public static void main(String[] args)
{
//variable declaration
int a,b,temp;
a=10;
b=20;
//by this method number would swap
temp=a;
a=b;
b=temp;
// print method
System.out.println("b="+b);
System.out.println("a="+a);
}
}

Type your Input in Java program

// main class 
class input
{
// main function
public static void main(String args[])
{
//print function
System.out.println("hello");
System.out.println(args[0]);
}
}

Output :- Hello 
               Type any name.

First hello world java program

//Declaration of class
class welcome
{
//main function
public static void main(String args[])
{

//print function

System.out.println("Hello World");
}
}

Output: Hello World.