How to replace all occurrences of a string in Java

Question

I have this string:

"Test abc test test abc test test test abc test test abc"

Doing

str = str.replace('abc', '');

seems to only remove the first occurrence of abc in the string above. How can I replace all occurrences of it?

Answer 1

Just follow this oneliner regex adding the case-sensitivity, so if you do "ABC", it would act the same as that for "abc".

str = str.replace(/abc/gi, "");

Answer 2

Here's a string prototype function based on the accepted answer:

String.prototype.replaceAll = function (find, replace) {
    var str = this;
    return str.replace(new RegExp(find, 'g'), replace);
};

EDIT

If your find will contain special characters then you need to escape them:

String.prototype.replaceAll = function (find, replace) {
    var str = this;
    return str.replace(new RegExp(find.replace(/[-\/\\^$*+?.()|[\]{}]/g, '\\$&'), 'g'), replace);
};

Fiddle: http://jsfiddle.net/cdbzL/

Answer 3

function replaceAll(str, find, replace) {
  var i = str.indexOf(find);
  if (i > -1){
    str = str.replace(find, replace); 
    i = i + replace.length;
    var st2 = str.substring(i);
    if(st2.indexOf(find) > -1){
      str = str.substring(0,i) + replaceAll(st2, find, replace);
    }       
  }
  return str;
}

Answer 4

If you are trying to ensure that the string you are looking for won't exist even after the replacement, you need to use a loop.

For example:

var str = 'test aabcbc';
str = str.replace(/abc/g, '');

When complete, you will still have 'test abc'!

The simplest loop to solve this would be:

var str = 'test aabcbc';
while (str != str.replace(/abc/g, '')){
   str.replace(/abc/g, '');
}

But that runs the replacement twice for each cycle. Perhaps (at risk of being voted down) that can be combined for a slightly more efficient but less readable form:

var str = 'test aabcbc';
while (str != (str = str.replace(/abc/g, ''))){}
// alert(str); alerts 'test '!

This can be particularly useful when looking for duplicate strings.
For example, if we have 'a,,,b' and we wish to remove all duplicate commas.
[In that case, one could do .replace(/,+/g,','), but at some point the regex gets complex and slow enough to loop instead.]

Answer 5

str = str.replace(/abc/g, '');

In response to comment:

var find = 'abc';
var re = new RegExp(find, 'g');

str = str.replace(re, '');

In response to Click Upvote's comment, you could simplify it even more:

function replaceAll(str, find, replace) {
    return str.replace(new RegExp(find, 'g'), replace);
}

Note: Regular expressions contain special (meta) characters, and as such it is dangerous to blindly pass an argument in the find function above without pre-processing it to escape those characters. This is covered in the Mozilla Developer Network's JavaScript Guide on Regular Expressions, where they present the following utility function:

function escapeRegExp(str) {
    return str.replace(/([.*+?^=!:${}()|\[\]\/\\])/g, "\\$1");
}

So in order to make the replaceAll() function above safer, it could be modified to the following if you also include escapeRegExp:

function replaceAll(str, find, replace) {
    return str.replace(new RegExp(escapeRegExp(find), 'g'), replace);
}

Answer 6

I like this method (it looks a little cleaner):

text = text.replace(new RegExp("cat","g"), "dog");