Write a java program to find Repeating set of characters in a string.

Get a string and a positive integer n as input. The last n characters should repeat the number of times given as second input. Write code to repeat the set of characters from the given string.

The return type of the output is a string with repeated n characters.

Input and Output Format

• Input consists of a string and a positive integer n.
• Output is a string with repeated characters.

Refer sample output for formatting specifications

Sample Input 1:

codebun

3

Sample Output 1:

codebunbunbunbun

Sample Input 2:

java

2

Sample Output 2:

javavava

Find the repeating set of characters in a string in Java

Following are the steps to find the repeating set of characters in a string:

• Input string and integer value from the user.
• Pass both of them to the lengthiestString() method.
• Inside the method, create an empty string buffer to hold the updated string.
• First, append the input string to the string buffer.
• Use for loop and traverse over the string and get the substring from the string and repeat them for the given ‘n’ integer values.
• At last, append it to the string buffer.

package com.demo2;

import java.util.Scanner;

public class RepeatingString {
public static void main(String[] args) {
Scanner s = new Scanner(System.in);
System.out.println("enter the String:");
String s1 = s.nextLine();
int n = s.nextInt();
System.out.println("the lengthiest string is:" + lengthiestString(s1, n));
}

public static String lengthiestString(String s1, int n) {
StringBuffer sb = new StringBuffer();
sb.append(s1);
for (int i = 0; i < n; i++) {
sb.append(s1.substring(s1.length() - n, s1.length()));
}
return sb.toString();
}
}

Output

Frequency of Repeating Character using HashMap

Get a string and a character as input. Write code to find the frequency of repeating characters from the given string.

Input and Output Format

• Input consists of a string.
• Output is an integer.

Refer sample output for formatting specifications

Sample Input :

old is gold

o

Sample Output :

2

Following are the steps to count the number of repeating characters:

• Input string and character from the user.
• Pass the character to the repeatingChars() method.
• Inside the method, create an empty HashMap.
• Iterate over each character of the input string and perform the following operation:
  • If the character is not present yet in the HashMap, it means it is the first time the character appears in the String; then, set the count as one.
  • If the character were already in the String, then increase the count and add it to the map.
• At last, return the map value.

package com.demo2;

import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;

public class RepeatingString {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        String str = scanner.nextLine();
        Map<Character,Integer> m1 = repeatingChars(str);
        System.out.println("Enter character");
        char c = scanner.next().charAt(0);
        System.out.println(c+" is repeated "+m1.get(c)+" times");
    }

    private static Map<Character, Integer> repeatingChars(String str) {
        Map<Character,Integer> map = new HashMap<>();
        for(Character character: str.toCharArray()){
            if(map.get(character)!=null){
                int count = map.get(character)+1;
                map.put(character,count);
            }
            else {
                map.put(character,1);
            }
        }
        return map;
    }
}

Output

Thus, in this way, we find the repeating sets of characters in Java.