Replace method doesn't work properly

Question

Hello I have a string and when I try to use replace method in for loop it doesn't work

String phrase="hello friend";
String[] wordds=phrase.split(" ");
String newPhrase="sup friendhello weirdo";
for (int g=0;g<2;g++)
{          
   finalPhrase+=newPhrase.replace(wordds[g],"");
}   
System.out.println(finalPhrase);

It prints out sup hello weirdo and I expect it to print sup weirdo.

What am I doing wrong?

Why do you append `+=` the replaced input? – Nov 03 '13 at 15:57 — , Nov 03 '13 at 15:57
Strings are immutable. – Sotirios Delimanolis Nov 03 '13 at 16:01 — Sotirios Delimanolis, Nov 03 '13 at 16:01

score 5 · Answer 1 · answered Nov 03 '13 at 15:59

Let's debug it together.

wordds = ["hello", "friend"].

newPhrase = "sup friendhello weirdo".

Then you're running on some g from 0 to 1 (Should be from 0 to wordds.length.

newPhrase.replace(wordds[g],""); will indeed replace as you want, but when you debug your program, you'll notice that you are using += instead of:

newPhrase=newPhrase.replace(wordds[g],"");

Tip for life: use the debugger, it's there to help you.

upog · Answer 2 · 2013-11-03T16:27:44.817

4

Try this:

String phrase = "hello friend";
String[] wordds = phrase.split(" ");
String newPhrase = "sup friendhello weirdo";
for (int g = 0; g < 2 ; g++) {          
  newPhrase = newPhrase.replace(wordds[g], "");
}   
System.out.println(newPhrase);

===================================================

updated

few things that you need to correct

you need to remove concat oprator (+), when you try to replace particular word in a sentence. Just assign it after replacing
for each time you enter the loop you are taking the initial declared string, instead you need to use the string which is getting updated each time

edited Nov 03 '13 at 16:27

answered Nov 03 '13 at 16:00

upog

4,965
8
42
81

It may seem trivial, but you should add an explanation. – Steve P. Nov 03 '13 at 16:07
@SteveP added the explanantion – upog Nov 03 '13 at 16:18

Unix von Bash · Answer 3 · 2013-11-03T16:00:17.130

1

what are you doing, is keep append the replaced Phrase to another one

newPhrase = newPhrase.replace(wordds[g],"");

edited Nov 03 '13 at 16:00

answered Nov 03 '13 at 15:58

Unix von Bash

735
5
20

2

You need to add some explanation - code only answers don't help the OP. – Boris the Spider Nov 03 '13 at 15:58

Marko Topolnik · Answer 4 · 2013-11-03T17:21:08.320

Apart from the suggestions of an immediate fix, you can also consider a regex-based solution, with no loops:

String phrase="hello friend";
String regex=phrase.replace(' ', '|');
String newPhrase="sup friendhello weirdo";
String finalPhrase=newPhrase.replaceAll(regex,"");
System.out.println(finalPhrase);

or, more succinctly:

System.out.println("sup friendhello weirdo"
                   .replaceAll("hello friend".replace(' ','|'), 
                               ""));

score 0 · Answer 5 · edited May 23 '17 at 12:14

This should do the trick:

String phrase="hello friend";
String[] wordds=phrase.split(" ");
String newPhrase="sup friendhello weirdo";
String finalPhrase=newPhrase;
for (int g=0;g<wordds.length;g++)
{          
   finalPhrase=finalPhrase.replace(wordds[g],"");
}   
System.out.println(finalPhrase);

First you assign finalPhrase to your newPhrase. Then you iterate over all split words (i've changed your magic constant 2 into number of split words wordds.length. Every word will be replaced in the finalPhrase string. The resulting string looks like sup weirdo (it has two spaces between words).

You can clean extra spaces using the answer from here:

System.out.println(finalPhrase.trim().replaceAll(" +", " "));

Replace method doesn't work properly

5 Answers5