Hello World example
/*
Java Hello World example.
*/
public class HelloWorldExample{
public static void main(String args[]){
/*
Use System.out.println() to print on console.
*/
System.out.println("Hello World !");
}
}
/*
OUTPUT of the above given Java Hello World Example would be :
Hello World !
*/
Java Class example
/*
Java Class example.
This Java class example describes how class is defined and being used
in Java language.
Syntax of defining java class is,
<modifier> class <class-name>{
// members and methods
}
*/
public class JavaClassExample{
/*
Syntax of defining memebers of the java class is,
<modifier> type <name>;
*/
private String name;
/*
Syntax of defining methods of the java class is,
<modifier> <return-type> methodName(<optional-parameter-list>) <exception-list>{
...
}
*/
public void setName(String n){
//set passed parameter as name
name = n;
}
public String getName(){
//return the set name
return name;
}
//main method will be called first when program is executed
public static void main(String args[]){
/*
Syntax of java object creation is,
<class-name> object-name = new <class-constructor>;
*/
JavaClassExample javaClassExample = new JavaClassExample();
//set name member of this object
javaClassExample.setName("Visitor");
// print the name
System.out.println("Hello " + javaClassExample.getName());
}
}
/*
OUTPUT of the above given Java Class Example would be :
Hello Visitor
*/
Calculate Circle Area using Java Example
/*
Calculate Circle Area using Java Example
This Calculate Circle Area using Java Example shows how to calculate
area of circle using it's radius.
*/
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
public class CalculateCircleAreaExample {
public static void main(String[] args) {
int radius = 0;
System.out.println("Please enter radius of a circle");
try
{
//get the radius from console
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
radius = Integer.parseInt(br.readLine());
}
//if invalid value was entered
catch(NumberFormatException ne)
{
System.out.println("Invalid radius value" + ne);
System.exit(0);
}
catch(IOException ioe)
{
System.out.println("IO Error :" + ioe);
System.exit(0);
}
/*
* Area of a circle is
* pi * r * r
* where r is a radius of a circle.
*/
//NOTE : use Math.PI constant to get value of pi
double area = Math.PI * radius * radius;
System.out.println("Area of a circle is " + area);
}
}
/*
Output of Calculate Circle Area using Java Example would be
Please enter radius of a circle
19
Area of a circle is 1134.1149479459152
Calculate Circle Perimeter using Java Example
/*
Calculate Circle Perimeter using Java Example
This Calculate Circle Perimeter using Java Example shows how to calculate
Perimeter of circle using it's radius.
*/
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
public class CalculateCirclePerimeterExample {
public static void main(String[] args) {
int radius = 0;
System.out.println("Please enter radius of a circle");
try
{
//get the radius from console
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
radius = Integer.parseInt(br.readLine());
}
//if invalid value was entered
catch(NumberFormatException ne)
{
System.out.println("Invalid radius value" + ne);
System.exit(0);
}
catch(IOException ioe)
{
System.out.println("IO Error :" + ioe);
System.exit(0);
}
/*
* Perimeter of a circle is
* 2 * pi * r
* where r is a radius of a circle.
*/
//NOTE : use Math.PI constant to get value of pi
double perimeter = 2 * Math.PI * radius;
System.out.println("Perimeter of a circle is " + perimeter);
}
}
/*
Output of Calculate Circle Perimeter using Java Example would be
Please enter radius of a circle
19
Perimeter of a circle is 119.38052083641213
*/
Calculate Rectangle Area using Java Example
/*
Calculate Rectangle Area using Java Example
This Calculate Rectangle Area using Java Example shows how to calculate
area of Rectangle using it's length and width.
*/
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
public class CalculateRectArea {
public static void main(String[] args) {
int width = 0;
int length = 0;
try
{
//read the length from console
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
System.out.println("Please enter length of a rectangle");
length = Integer.parseInt(br.readLine());
//read the width from console
System.out.println("Please enter width of a rectangle");
width = Integer.parseInt(br.readLine());
}
//if invalid value was entered
catch(NumberFormatException ne)
{
System.out.println("Invalid value" + ne);
System.exit(0);
}
catch(IOException ioe)
{
System.out.println("IO Error :" + ioe);
System.exit(0);
}
/*
* Area of a rectangle is
* length * width
*/
int area = length * width;
System.out.println("Area of a rectangle is " + area);
}
}
/*
Output of Calculate Rectangle Area using Java Example would be
Please enter length of a rectangle
10
Please enter width of a rectangle
15
Area of a rectangle is 150
*/
Calculate Rectangle Perimeter using Java Example
/*
Calculate Rectangle Perimeter using Java Example
This Calculate Rectangle Perimeter using Java Example shows how to calculate
perimeter of Rectangle using it's length and width.
*/
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
public class CalculateRectPerimeter {
public static void main(String[] args) {
int width = 0;
int length = 0;
try
{
//read the length from console
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
System.out.println("Please enter length of a rectangle");
length = Integer.parseInt(br.readLine());
//read the width from console
System.out.println("Please enter width of a rectangle");
width = Integer.parseInt(br.readLine());
}
//if invalid value was entered
catch(NumberFormatException ne)
{
System.out.println("Invalid value" + ne);
System.exit(0);
}
catch(IOException ioe)
{
System.out.println("IO Error :" + ioe);
System.exit(0);
}
/*
* Perimeter of a rectangle is
* 2 * (length + width)
*/
int perimeter = 2 * (length + width);
System.out.println("Perimeter of a rectangle is " + perimeter);
}
}
/*
Output of Calculate Rectangle Perimeter using Java Example would be
Please enter length of a rectangle
10
Please enter width of a rectangle
15
Perimeter of a rectangle is 50
*/
Even Odd Number Example
/*
Even Odd Number Example
This Java Even Odd Number Example shows how to check if the given
number is even or odd.
*/
public class FindEvenOrOddNumber {
public static void main(String[] args) {
//create an array of 10 numbers
int[] numbers = new int[]{1,2,3,4,5,6,7,8,9,10};
for(int i=0; i < numbers.length; i++){
/*
* use modulus operator to check if the number is even or odd.
* If we divide any number by 2 and reminder is 0 then the number is
* even, otherwise it is odd.
*/
if(numbers[i]%2 == 0)
System.out.println(numbers[i] + " is even number.");
else
System.out.println(numbers[i] + " is odd number.");
}
}
}
/*
Output of the program would be
1 is odd number.
2 is even number.
3 is odd number.
4 is even number.
5 is odd number.
6 is even number.
7 is odd number.
8 is even number.
9 is odd number.
10 is even number.
*/
Find Largest and Smallest Number in an Array Example
/*
Find Largest and Smallest Number in an Array Example
This Java Example shows how to find largest and smallest number in an
array.
*/
public class FindLargestSmallestNumber {
public static void main(String[] args) {
//array of 10 numbers
int numbers[] = new int[]{32,43,53,54,32,65,63,98,43,23};
//assign first element of an array to largest and smallest
int smallest = numbers[0];
int largetst = numbers[0];
for(int i=1; i< numbers.length; i++)
{
if(numbers[i] > largetst)
largetst = numbers[i];
else if (numbers[i] < smallest)
smallest = numbers[i];
}
System.out.println("Largest Number is : " + largetst);
System.out.println("Smallest Number is : " + smallest);
}
}
/*
Output of this program would be
Largest Number is : 98
Smallest Number is : 23
*/
Java Factorial Example
/*
Java Factorial Example
This Java Factorial Example shows how to calculate factorial of
a given number using Java.
*/
public class NumberFactorial {
public static void main(String[] args) {
int number = 5;
/*
* Factorial of any number is !n.
* For example, factorial of 4 is 4*3*2*1.
*/
int factorial = number;
for(int i =(number - 1); i > 1; i--)
{
factorial = factorial * i;
}
System.out.println("Factorial of a number is " + factorial);
}
}
/*
Output of the Factorial program would be
Factorial of a number is 120
*/
Java Factorial Using Recursion Example
Submitted By: Naresh
/*
Java Factorial Using Recursion Example
This Java example shows how to generate factorial of a given number
using recursive function.
*/
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
public class JavaFactorialUsingRecursion {
public static void main(String args[]) throws NumberFormatException, IOException{
System.out.println("Enter the number: ");
//get input from the user
BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
int a = Integer.parseInt(br.readLine());
//call the recursive function to generate factorial
int result= fact(a);
System.out.println("Factorial of the number is: " + result);
}
static int fact(int b)
{
if(b <= 1)
//if the number is 1 then return 1
return 1;
else
//else call the same function with the value - 1
return b * fact(b-1);
}
}
/*
Output of this Java example would be
Enter the number:
5
Factorial of the number is: 120
*/
Java Interface example
/*
Java Interface example.
This Java Interface example describes how interface is defined and
being used in Java language.
Syntax of defining java interface is,
<modifier> interface <interface-name>{
//members and methods()
}
*/
//declare an interface
interface IntExample{
/*
Syntax to declare method in java interface is,
<modifier> <return-type> methodName(<optional-parameters>);
IMPORTANT : Methods declared in the interface are implicitly public and abstract.
*/
public void sayHello();
}
}
/*
Classes are extended while interfaces are implemented.
To implement an interface use implements keyword.
IMPORTANT : A class can extend only one other class, while it
can implement n number of interfaces.
*/
public class JavaInterfaceExample implements IntExample{
/*
We have to define the method declared in implemented interface,
or else we have to declare the implementing class as abstract class.
*/
public void sayHello(){
System.out.println("Hello Visitor !");
}
public static void main(String args[]){
//create object of the class
JavaInterfaceExample javaInterfaceExample = new JavaInterfaceExample();
//invoke sayHello(), declared in IntExample interface.
javaInterfaceExample.sayHello();
}
}
/*
OUTPUT of the above given Java Interface example would be :
Hello Visitor !
*/
Reverse Number using Java
/*
Reverse Number using Java
This Java Reverse Number Example shows how to reverse a given number.
*/
public class ReverseNumber {
public static void main(String[] args) {
//original number
int number = 1234;
int reversedNumber = 0;
int temp = 0;
while(number > 0){
//use modulus operator to strip off the last digit
temp = number%10;
//create the reversed number
reversedNumber = reversedNumber * 10 + temp;
number = number/10;
}
//output the reversed number
System.out.println("Reversed Number is: " + reversedNumber);
}
}
/*
Output of this Number Reverse program would be
Reversed Number is: 4321
*/
Swap Numbers Java Example
/*
Swap Numbers Java Example
This Swap Numbers Java Example shows how to
swap value of two numbers using java.
*/
public class SwapElementsExample {
public static void main(String[] args) {
int num1 = 10;
int num2 = 20;
System.out.println("Before Swapping");
System.out.println("Value of num1 is :" + num1);
System.out.println("Value of num2 is :" +num2);
//swap the value
swap(num1, num2);
}
private static void swap(int num1, int num2) {
int temp = num1;
num1 = num2;
num2 = temp;
System.out.println("After Swapping");
System.out.println("Value of num1 is :" + num1);
System.out.println("Value of num2 is :" +num2);
}
}
/*
Output of Swap Numbers example would be
Before Swapping
Value of num1 is :10
Value of num2 is :20
After Swapping
Value of num1 is :20
Value of num2 is :10
*/
Swap Numbers Without Using Third Variable Java Example
/*
Swap Numbers Without Using Third Variable Java Example
This Swap Numbers Java Example shows how to
swap value of two numbers without using third variable using java.
*/
public class SwapElementsWithoutThirdVariableExample {
public static void main(String[] args) {
int num1 = 10;
int num2 = 20;
System.out.println("Before Swapping");
System.out.println("Value of num1 is :" + num1);
System.out.println("Value of num2 is :" +num2);
//add both the numbers and assign it to first
num1 = num1 + num2;
num2 = num1 - num2;
num1 = num1 - num2;
System.out.println("Before Swapping");
System.out.println("Value of num1 is :" + num1);
System.out.println("Value of num2 is :" +num2);
}
}
/*
Output of Swap Numbers Without Using Third Variable example would be
Before Swapping
Value of num1 is :10
Value of num2 is :20
Before Swapping
Value of num1 is :20
Value of num2 is :10
*/
