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

The previous answers are way too complicated. Just use the replace function like this:

str.replace(/your_regex_pattern/g, replacement_string);

Example:

var str = "Test abc test test abc test test test abc test test abc";

var res = str.replace(/[abc]+/g, "");

console.log(res);

Answer 2

while (str.indexOf('abc') !== -1)
{
    str = str.replace('abc', '');
}

Answer 3

This is the fastest version that doesn't use regular expressions.

Revised jsperf

replaceAll = function(string, omit, place, prevstring) {
  if (prevstring && string === prevstring)
    return string;
  prevstring = string.replace(omit, place);
  return replaceAll(prevstring, omit, place, string)
}

It is almost twice as fast as the split and join method.

As pointed out in a comment here, this will not work if your omit variable contains place, as in: replaceAll("string", "s", "ss"), because it will always be able to replace another occurrence of the word.

There is another jsperf with variants on my recursive replace that go even faster (http://jsperf.com/replace-all-vs-split-join/12)!

• Update July 27th 2017: It looks like RegExp now has the fastest performance in the recently released Chrome 59.

Answer 4

For the sake of completeness, I got to thinking about which method I should use to do this. There are basically two ways to do this as suggested by the other answers on this page.

Note: In general, extending the built-in prototypes in JavaScript is generally not recommended. I am providing as extensions on the String prototype simply for purposes of illustration, showing different implementations of a hypothetical standard method on the String built-in prototype.

---

Regular Expression Based Implementation

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

Split and Join (Functional) Implementation

String.prototype.replaceAll = function(search, replacement) {
    var target = this;
    return target.split(search).join(replacement);
};

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Not knowing too much about how regular expressions work behind the scenes in terms of efficiency, I tended to lean toward the split and join implementation in the past without thinking about performance. When I did wonder which was more efficient, and by what margin, I used it as an excuse to find out.

On my Chrome Windows 8 machine, the regular expression based implementation is the fastest, with the split and join implementation being 53% slower. Meaning the regular expressions are twice as fast for the lorem ipsum input I used.

Check out this benchmark running these two implementations against each other.

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As noted in the comment below by @ThomasLeduc and others, there could be an issue with the regular expression-based implementation if search contains certain characters which are reserved as special characters in regular expressions. The implementation assumes that the caller will escape the string beforehand or will only pass strings that are without the characters in the table in Regular Expressions (MDN).

MDN also provides an implementation to escape our strings. It would be nice if this was also standardized as RegExp.escape(str), but alas, it does not exist:

function escapeRegExp(str) {
  return str.replace(/[.*+?^${}()|[\]\\]/g, "\\$&"); // $& means the whole matched string
}

We could call escapeRegExp within our String.prototype.replaceAll implementation, however, I'm not sure how much this will affect the performance (potentially even for strings for which the escape is not needed, like all alphanumeric strings).

Answer 5

If the string contain similar pattern like abccc, you can use this:

str.replace(/abc(\s|$)/g, "")

Answer 6

If what you want to find is already in a string, and you don't have a regex escaper handy, you can use join/split:

    function replaceMulti(haystack, needle, replacement)
    {
        return haystack.split(needle).join(replacement);
    }

    someString = 'the cat looks like a cat';
    console.log(replaceMulti(someString, 'cat', 'dog'));