1) Write a Java program to find whether a number is an Armstrong number.
import java.util.Scanner;
public class ArmstrongNumber {
public static void main(String[] args){
int c=0,a,temp;
Scanner sc = new Scanner(System.in);
System.out.println("Enter a number");
int num = sc.nextInt();
temp = num;
while(num>0){
a=num%10;
num=num/10;
c=c+(a*a*a);
}
if(temp==c) {
System.out.println(temp + " is an Armstrong number");
} else System.out.println(temp + " is not an armstrong number");
}
}
OUTPUT: Enter a number 153 153 is an Armstrong number Process finished with exit code 0
2) Write a Java program to compare 2 strings.
import java.util.Scanner;
public class CompareTwoStrings {
public static void main(String[] args){
Scanner sc = new Scanner(System.in);
System.out.println("Enter first string");
String first = sc.next();
System.out.println("Enter second string");
String second = sc.next();
compare(first,second);
}
public static void compare(String s1, String s2){
if(s1.compareTo(s2)==0) {
System.out.println("Strings are equal");
} else {
System.out.println("Strings are not equal");
}
}
}
OUTPUT: Enter first string automation Enter second string java Strings are not equal Process finished with exit code 0
3) Write a Java program to find largest number in an array.
public class FindLargestNumberInArray {
static int array[] = {21,98,13,9,34};
public static void main(String[] args){
int maxNumber = findLargestNumber();
System.out.println("Maximum number in the array: "+ maxNumber);
}
private static int findLargestNumber(){
int max = array[0];
for(int i =0;i<array.length;i++){
if(array[i]>max)
max = array[i];
}
return max;
}
}
OUTPUT: Maximum number in the array: 98 Process finished with exit code 0
4) Write a Java program to find whether number is prime.
import java.util.Scanner;
public class FindNumberIsPrime {
public static void main(String[] args){
boolean flag = false;
System.out.println("Enter input number");
Scanner sc = new Scanner(System.in);
int num = sc.nextInt();
for(int i=2;i<=num/2;i++){
if(num%i==0){
flag = true;
break;
}
}
if(!flag){
System.out.println(num + " is a prime number");
} else{
System.out.println(num + " is not a prime number");
}
}
}
OUTPUT: Enter input number 23 23 is a prime number Process finished with exit code 0
5) Write a Java program to find whether number is even or odd.
import java.util.Scanner;
public class FindOddEvenNumbers {
public static void main(String[] args){
Scanner sc= new Scanner(System.in);
System.out.println("Enter a number: ");
int inputNumber = sc.nextInt();
findNumber(inputNumber);
}
public static void findNumber(int number){
if(number%2!=0){
System.out.println("Number is odd");
}
else {
System.out.println("Number is even");
}
}
}
OUTPUT: Enter a number: 29 Number is odd Process finished with exit code 0
6) Write a Java program to find whether number is Palindrome.
import java.util.Scanner;
public class PalindromeNumber {
public static void main(String[] args){
int r,sum=0,temp;
Scanner sc = new Scanner(System.in);
System.out.println("Enter a number");
int n = sc.nextInt();
temp=n;
while (n > 0) {
r = n%10;
sum = (sum*10) + r;
n=n/10;
}
if(temp==sum)
System.out.println("Number is palindrome");
else
System.out.println("Number is not palindrome");
}
}
OUTPUT: Enter a number 545 Number is palindrome Process finished with exit code 0
7) Write a Java program to reverse a number.
import java.util.Scanner;
public class ReverseNumber {
public static void main(String[] args){
Scanner sc = new Scanner(System.in);
System.out.println("Enter the number");
int num = sc.nextInt();
reverseNumber(num);
}
public static void reverseNumber(int number){
int reverse = 0;
while(number!=0){
int digit = number % 10;
reverse = reverse * 10 + digit;
number = number/10;
}
System.out.println("Reversed number " + reverse);
}
}
OUTPUT: Enter the number 654 Reversed number 456 Process finished with exit code 0
8) Write a Java program to reverse a string.
import java.util.Scanner;
public class ReverseString {
public static void main(String[] args){
Scanner sc = new Scanner(System.in);
System.out.println("Enter input string");
String s1 = sc.next();
String s2 = reverseString(s1);
System.out.println("Reversed String is: "+s2);
}
public static String reverseString(String s){
String rev="";
char[] arr = s.toCharArray();
for(int i=arr.length-1;i>=0;i--)
rev = rev + arr[i];
return rev;
}
}
OUTPUT: Enter input string automation Reversed String is: noitamotua Process finished with exit code 0
9) Write a Java program to swap numbers without a variable.
public class SwapNumberWithoutVariable {
public static void main(String[] args) {
int x = 10;
int y = 5;
System.out.println("Before swapping: " + "x is " + x + " and " + "y is " + y);
x = x + y;
y = x - y;
x = x - y;
System.out.println("After swapping: " + " x is " + x + " and " + "y is "+ y);
}
}
OUTPUT: Before swapping: x is 10 and y is 5 After swapping: x is 5 and y is 10 Process finished with exit code 0
10) Write a Java program to reverse a sentence word by word.
public class ReverseSentenceWordByWord {
public static void main(String[] args){
String sentence = "Java Interview Questions";
String reversedSentence = reverseSentence(sentence);
System.out.println(reversedSentence);
}
public static String reverseSentence(String sentence){
String reverse = "";
String[] words = sentence.split("\\s");
for(int i=words.length-1;i>=0;i--){
reverse = reverse + words[i] + " ";
}
return reverse;
}
}
OUTPUT: Original sentence is: Java Interview Questions Reversed sentence is: Questions Interview Java Process finished with exit code 0
11) Write a Java program to find duplicate numbers in an Array.
import java.util.HashSet;
public class FindDuplicateElementsInArray {
public static void main(String[] args){
Integer[] inputArray = {2,3,4,5,1,2,3};
HashSet<Integer> set = new HashSet<>();
for(int number: inputArray){
if(!set.add(number))
{
System.out.println("Duplicate element in the array is "+ number);
}
}
}
}
OUTPUT: Duplicate element in the array is 2 Duplicate element in the array is 3 Process finished with exit code 0
12) Write a Java program to find frequency of characters in String.
import java.util.HashMap;
import java.util.Map;
public class FindFrequencyOfCharactersInString {
public static void main(String[] args){
Map<Character,Integer> map = new HashMap<>();
map = findFrequency("Java J2EE Java JSP J2EE");
for(Map.Entry<Character,Integer> entry: map.entrySet()){
System.out.println("Frequency of character " + entry.getKey() + " is "+ entry.getValue());
}
}
public static Map<Character,Integer> findFrequency(String input){
char[] arr = input.toLowerCase().replaceAll("\\s+","").toCharArray();
Map<Character,Integer> frequency = new HashMap<>();
for(char c: arr){
if(frequency.containsKey(c)){
frequency.put(c,frequency.get(c) + 1);
}
else{
frequency.put(c,1);
}
}
return frequency;
}
}
OUTPUT: Frequency of character p is 1 Frequency of character a is 4 Frequency of character 2 is 2 Frequency of character s is 1 Frequency of character e is 4 Frequency of character v is 2 Frequency of character j is 5 Process finished with exit code 0
13) Write a Java program to perform binary search of an element.
// Java implementation of recursive Binary Search
class BinarySearch {
int binarySearch(int arr[], int l, int r, int x)
{
if (r >= l) {
int mid = l + (r - l) / 2;
// If the element is present at the middle itself
if (arr[mid] == x)
return mid;
// If element is smaller than mid, then it can only be present in left subarray
if (arr[mid] > x)
return binarySearch(arr, l, mid - 1, x);
// Else the element can only be present in right subarray
return binarySearch(arr, mid + 1, r, x);
}
// If element is not present in array
return -1;
}
public static void main(String args[])
{
BinarySearch bs = new BinarySearch();
int arr[] = { 2, 3, 4, 10, 40 };
int n = arr.length;
int x = 10;
int result = bs.binarySearch(arr, 0, n - 1, x);
if (result == -1)
System.out.println("Element not present");
else
System.out.println("Element found at index " + result);
}
}
OUTPUT: Element found at index 3 Process finished with exit code 0
14) Write a Java program to perform linear search of an element.
public class LinearSearch {
static int search(int arr[], int n, int x){
for(int i = 0;i<n;i++){
if(arr[i] == x)
return i;
}
return -1;
}
public static void main(String[] args){
int[] arr = {5,1,9,4,3,8};
int n = arr.length;
int x = 4;
int index = search(arr,n,x);
if(index == -1){
System.out.println("Element is not present in the array");
}
else
System.out.println("Element found at position " + index);
}
}
OUTPUT: Element found at position 3 Process finished with exit code 0
15) Write a Java program to sort numbers using Bubble sort.
class BubbleSort
{
void bubbleSort(int arr[]) {
int n = arr.length;
for (int i = 0; i < n-1; i++)
for (int j = 0; j < n-i-1; j++)
if (arr[j] > arr[j+1])
{
int temp = arr[j];
arr[j] = arr[j+1];
arr[j+1] = temp;
}
}
void printArray(int arr[]) {
int n = arr.length;
for (int i=0; i<n; ++i)
System.out.print(arr[i] + " ");
System.out.println();
}
public static void main(String args[]) {
BubbleSort bs = new BubbleSort();
int arr[] = {64, 34, 25, 12, 22, 11, 90};
bs.bubbleSort(arr);
System.out.println("Sorted array");
bs.printArray(arr);
}
}
OUTPUT: Sorted array 11 12 22 25 34 64 90 Process finished with exit code 0
16) Write a Java program to print Floyd triangle.
import java.util.Scanner;
public class FloydTriangle {
public static void main(String[] args){
Scanner sc = new Scanner(System.in);
System.out.println("Enter the number of rows");
int rows = sc.nextInt();
printFloydTriangle(rows);
}
public static void printFloydTriangle(int n){
int number = 1;
for(int i=0;i<n;i++){
for(int j=0;j<=i;j++){
System.out.print(number +" ");
number++;
}
System.out.println();
}
}
}
OUTPUT: Enter the number of rows 5 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Process finished with exit code 0
17) Write a Java program to generate a random number.
import java.util.Random;
public class GenerateRandomNumber {
public static void main(String[] args){
Random rand = new Random();
int r1 = rand.nextInt(1000);
System.out.println("Random numbers: "+ r1);
}
}
OUTPUT: Random numbers: 876 Process finished with exit code 0
18) Write a Java program to open a Notepad application.
import java.io.IOException;
public class OpenNotepad {
public static void main(String[] args){
Runtime rs = Runtime.getRuntime();
try{
rs.exec("notepad");
}
catch (IOException e){
System.out.println(e);
}
}
}
19) Write a Java program to get date and time in specific format.
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.time.LocalDate;
import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;
import java.util.Calendar;
import java.util.Date;
public class GetDateAndTime {
private static final DateFormat sdf = new SimpleDateFormat("yyyy/MM/dd HH:mm:ss");
private static final DateTimeFormatter dtf = DateTimeFormatter.ofPattern("yyyy/MM/dd HH:mm:ss");
public static void main(String[] args) {
Date date = new Date();
System.out.println(sdf.format(date));
Calendar cal = Calendar.getInstance();
System.out.println(sdf.format(cal.getTime()));
LocalDateTime now = LocalDateTime.now();
System.out.println(dtf.format(now));
LocalDate localDate = LocalDate.now();
System.out.println(DateTimeFormatter.ofPattern("yyy/MM/dd").format(localDate));
}
}
OUTPUT: 2020/03/14 20:37:13 2020/03/14 20:37:13 2020/03/14 20:37:13 2020/03/14 Process finished with exit code 0
20) Write a Java program to find your IP address.
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.InetAddress;
import java.net.URL;
public class FindIPAddress {
public static void main(String[] args) throws Exception{
// Returns the instance of InetAddress containing local host name and address
InetAddress localhost = InetAddress.getLocalHost();
System.out.println("System IP Address : " + (localhost.getHostAddress()).trim());
// Find public IP address
String systemipaddress = "";
try
{
URL url_name = new URL("https://bot.whatismyipaddress.com");
BufferedReader sc = new BufferedReader(new InputStreamReader(url_name.openStream()));
// reads system IPAddress
systemipaddress = sc.readLine().trim();
}
catch (Exception e)
{
systemipaddress = "Cannot Execute Properly";
}
System.out.println("Public IP Address: " + systemipaddress +"\n");
}
}
OUTPUT: System IP Address : 192.168.0.0 Public IP Address: 11.99.77.111 Process finished with exit code 0
