Remove repeated characters in a string

Question

I need to write a static method that takes a String as a parameter and returns a new String obtained by replacing every instance of repeated adjacent letters with a single instance of that letter without using regular expressions. For example if I enter "maaaakkee" as a String, it returns "make". I already tried the following code, but it doesn't seem to display the last character. Here's my code:

import java.util.Scanner;
public class undouble {
    public static void main(String [] args){
        Scanner console = new Scanner(System.in);
        System.out.println("enter String: ");
        String str = console.nextLine();
        System.out.println(removeSpaces(str));
    }
public static String removeSpaces(String str){
    String ourString="";
    int j = 0;
    for (int i=0; i<str.length()-1 ; i++){
        j = i+1;
        if(str.charAt(i)!=str.charAt(j)){
            ourString+=str.charAt(i);
        }

    }

    return ourString;
    }
}

Solution 1

The problem is with your condition. You say compare i and i+1 in each iteration and in last iteration you have both i and j pointing to same location so it will never print the last character. Try this unleass you want to use regex to achive this:

EDIT:

public  void removeSpaces(String str){
        String ourString="";
        for (int i=0; i<str.length()-1 ; i++){
            if(i==0){
                ourString = ""+str.charAt(i);
            }else{
                if(str.charAt(i-1) != str.charAt(i)){
                    ourString = ourString +str.charAt(i);
                }
            }           
        }
        System.out.println(ourString);
    }

Solution 2

You could use regular expressions for that.

For instance:

String input = "ddooooonnneeeeee";
System.out.println(input.replaceAll("(.)\\1{1,}", "$1"));

Output:

done

Pattern explanation:

• "(.)\\1{1,}" means any character (added to group 1) followed by itself at least once
• "$1" references contents of group 1

Solution 3

maybe:

for (int i=1; i<str.length() ; i++){
    j = i+1;
    if(str.charAt(i)!=str.charAt(j)){
        ourString+=str.charAt(i);
    }
}