Cu466x - Online Java Compiler & Debugging Tool

/* package whatever; // don't place package name! */

import java.util.*;
import java.lang.*;
import java.io.*;

/* Name of the class has to be "Main" only if the class is public. */
import java.util.Scanner;

class UserMainCode {
    public String collapseRepeatedCharacters(String input1) {
        StringBuilder sb = new StringBuilder();
        int n = input1.length();
        int i = 0;

        while (i < n) {
            char current = input1.charAt(i);
            int j = i;
            while (j < n && input1.charAt(j) == current) {
                j++;
            }
            if (j - i >= 2) {
                sb.append('#');
            } else {
                sb.append(current);
            }
            i = j;
        }

        String intermediate = sb.toString();
        StringBuilder result = new StringBuilder();
        i = 0;
        while (i < intermediate.length()) {
            char current = intermediate.charAt(i);
            if (current == '#') {
                result.append('#');
                while (i < intermediate.length() && intermediate.charAt(i) == '#') {
                    i++;
                }
            } else {
                result.append(current);
                i++;
            }
        }

        return result.toString();
    }
}

class Ideone {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String input1 = sc.nextLine();

        UserMainCode obj = new UserMainCode();
        String result = obj.collapseRepeatedCharacters(input1);

        System.out.println(result);
    }
}