String Programs in Java

• 1. Count Unique Characters in String in Java.
• import java.util.ArrayList;
• import java.util.List;
• import java.util.Scanner;
• public class Main {
• public static void main(String[] args) {
• Scanner sc = new Scanner(System.in);
• String s1 = sc.nextLine();
• getvalues(s1);
• }
• public static void getvalues(String s1) {
• String s2 = s1.toLowerCase();
• StringBuffer sb = new StringBuffer(s2);
• int l = sb.length();
• int count = 0;
• for (int i = 0; i < l; i++) {
• count = 0;
• for (int j = i + 1; j < l; j++) {
• if (sb.charAt(i) == sb.charAt(j)) {
• sb.deleteCharAt(j);
• count++;
• j--;
• l--;
• }
• }
• if (count > 0) {
• sb.deleteCharAt(i);
• i--;
• l--;
• }
• }
• if (sb.length() == 0) {
• System.out.println(-1);
• } else
• System.out.println(sb.length());
• }
• }

2. Java program to reverse a string

import java.util.*;

class ReverseString
{
  public static void main(String args[])
  {
    String original, reverse = "";
    Scanner in = new Scanner(System.in);

    System.out.println("Enter a string to reverse");
    original = in.nextLine();

    int length = original.length();

    for (int i = length - 1 ; i >= 0 ; i--)
      reverse = reverse + original.charAt(i);

    System.out.println("Reverse of the string: " + reverse);
  }
}

Reverse a string in Java using StringBuffer class

class InvertString
{
  public static void main(String args[])
  {
     StringBuffer a = new StringBuffer("Java programming is fun");
     System.out.println(a.reverse());
  }
}

3. Java program asks the user to provide a string input, and checks it for the Palindrome String.

import java.util.Scanner; class ChkPalindrome { public static void main(String args[]) { String str, rev = ""; Scanner sc = new Scanner(System.in); System.out.println("Enter a string:"); str = sc.nextLine(); int length = str.length(); for ( int i = length - 1; i >= 0; i-- ) rev = rev + str.charAt(i); if (str.equals(rev)) System.out.println(str+" is a palindrome"); else System.out.println(str+" is not a palindrome"); } }

4. Java program to remove a particular character from a string.

class GFG 

{

static void removeChar(String s, char c)

{

    int j, count = 0, n = s.length();

    char []t = s.toCharArray();

    for (int i = j = 0; i < n; i++)

    {

        if (t[i] != c)

        t[j++] = t[i];

        else

            count++;

    }

      

    while(count > 0)

    {

        t[j++] = '\0';

        count--;

    }

      

    System.out.println(t);

}

  

// Driver Code

public static void main(String[] args) 

{

    String s = "geeksforgeeks";

    removeChar(s, 'g');

}

}




5. Write a code to prove that strings are immutable in java?

1. public class ProveStringImmutable {  
2.     public static void referenceCheck(Object x, Object y) {  
3.         if (x == y) {  
4.             System.out.println("Both pointing to the same reference");  
5.    
6.         } else {  
7.             System.out.println("Both are pointing to different reference");  
8.         }  
9.     }  
10.     public static void main(String[] args) {  
11.         String st1 = "Java";  
12.         String st2 = "Java";  
13.         System.out.println("Before Modification in st1");  
14.         referenceCheck(st1, st2);  
15.         st1 += "ava";  
16.         System.out.println("After Modification");  
17.         referenceCheck(st1, st2);  
18.     }  
19. }  

6.Write a Java program to count the number of words in a string?

1. public class WordCount {  
2.       static int wordcount(String string)  
3.         {  
4.           int count=0;  
5.       
6.             char ch[]= new char[string.length()];     
7.             for(int i=0;i<string.length();i++)  
8.             {  
9.                 ch[i]= string.charAt(i);  
10.                 if( ((i>0)&&(ch[i]!=' ')&&(ch[i-1]==' ')) || ((ch[0]!=' ')&&(i==0)) )  
11.                     count++;  
12.             }  
13.             return count;  
14.         }  
15.       public static void main(String[] args) {  
16.           String string ="    India Is My Country";  
17.          System.out.println(wordcount(string) + " words.");   
18.     }  
19. }  

7. Write a Java program to check whether two strings are anagram or not?

1. import java.util.Arrays;  
2.    
3. public class AnagramString {  
4.     static void isAnagram(String str1, String str2) {  
5.         String s1 = str1.replaceAll("\\s", "");  
6.         String s2 = str2.replaceAll("\\s", "");  
7.         boolean status = true;  
8.         if (s1.length() != s2.length()) {  
9.             status = false;  
10.         } else {  
11.             char[] ArrayS1 = s1.toLowerCase().toCharArray();  
12.             char[] ArrayS2 = s2.toLowerCase().toCharArray();  
13.             Arrays.sort(ArrayS1);  
14.             Arrays.sort(ArrayS2);  
15.             status = Arrays.equals(ArrayS1, ArrayS2);  
16.         }  
17.         if (status) {  
18.             System.out.println(s1 + " and " + s2 + " are anagrams");  
19.         } else {  
20.             System.out.println(s1 + " and " + s2 + " are not anagrams");  
21.         }  
22.     }  
23.    
24.     public static void main(String[] args) {  
25.         isAnagram("Keep", "Peek");  
26.         isAnagram("Mother In Law", "Hitler Woman");  
27.     }  
28. }