Delete duplicate characters from string

Question

I'm trying to delete duplicate characters from a string. For example if I enter the string abaqueru it should give me bqer with duplicate characters a and u deleted. However, instead the result is an unnecessary loop. Here is the code:

public class question {
/**
 * @param args the command line arguments
 */
public static void main(String[] args) {
 String s = "abaqueru";
 calculate(s);
 // TODO code application logic here
}
public static void calculate(String s){
 String result;
 for(int i = 0; i < s.length(); i++)
 {
 char c = s.charAt(i);
 char temp;
 temp=c;
 for(int j = 1; j < s.length(); j++)
 {
 char x = s.charAt(j);
 if(temp==x){
 s=s.replaceAll(""+temp,"");
 calculate(s);
 }
 }
 System.out.println(s);
 }
}

• Madhawa Priyashantha: don't change your question completely .ask new one if you have a another question
• Furkan: Sorry, i didnt know that.

Answer 1

String are immutable in java. After replaceall, you need to assign it back

s=s.replaceAll(""+temp,"");

If you didn't assign it back, the loop goes on forever.

That solves the stackoverflow error, I didn't concentrate on your actual logic :)

• Furkan: I corrected it thanks but i think i have algorithm problems also that taking me unnecessarry loops.

Answer 2

I will go with Suresh Atta's Answer which was leading to stack overflow error. I also checked your logic. Have made some necessary changes

public class Question {
 /**
 * @param args the command line arguments
 */
 public static void main(String[] args) {
 String s = "abaqueru";
 calculate(s);
 // TODO code application logic here
 }
 public static void calculate(String s){
 String result;
 for(int i = 0; i < s.length(); i++)
 {
 char c = s.charAt(i);
 char temp;
 temp=c;
 for(int j = i+1; j < s.length(); j++)
 {
 char x = s.charAt(j);
 if(temp==x){
 s=s.replaceAll(""+temp, "");
 break;
 // calculate(s);
 }
 }
 }
 System.out.println(s);
 }
}

However this can be further customized to achive performance in terms of space and time. Infact, more simpler logic can be used :)

Answer 3

Definitely go with Suresh Atta's answer! However, I figured I'd help glance over your code to help you find where some of your mistakes were.

I just glanced over your logic in the code though, and there is definitely some stuff worth glancing over. The most notable is that j is never used in the inner-for-loop. In fact, if you are using an IDE, it should warn you that j is never used.

UPDATE: Also, consider using String.valueOf(char c) instead of the s=s.replaceAll(""+temp,""); call you have in the if(temp==x) condition. That is, I assume that is so you could cast the character to a String? Then you can use String.append(), which you can read about on the link I sent you!

• Furkan: Yes, In there if i found any letter duplication in string, I change that duplicated letter with ""(space). and i use // ""+temp // for string parse
• daniel.caspers: If you don't use j in the inner for loop, all 3 character variables will be the same. Notice that you are grabbing the same character each time through the inner for loop, thus comparing it to a character it is guaranteed to be equal to. In other words, you are grabbing the character (at location i) j times.
• daniel.caspers: Also, any particular reason why you went with a recursive solution this way?
• Furkan: I replace i with j in second loop and I dont know how many different repeated letter in string so i decide to use recursion.