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