Difference between String replace() and replaceAll()

Q: What's the difference between the java.lang.String methods replace() and replaceAll(), other than that the latter uses regex.

A: Just the regex. They both replace all :)

http://docs.oracle.com/javase/8/docs/api/java/lang/String.html

PS:

There's also a replaceFirst() (which takes a regex)


Both replace() and replaceAll() replace all occurrences in the String.

Examples

I always find examples helpful to understand the differences.

replace()

Use replace() if you just want to replace some char with another char or some String with another String (actually CharSequence).

Example 1

Replace all occurrences of the character x with o. 

String myString = "__x___x___x_x____xx_";

char oldChar = 'x';
char newChar = 'o';

String newString = myString.replace(oldChar, newChar);
// __o___o___o_o____oo_

Example 2

Replace all occurrences of the string fish with sheep. 

String myString = "one fish, two fish, three fish";

String target = "fish";
String replacement = "sheep";

String newString = myString.replace(target, replacement);
// one sheep, two sheep, three sheep

replaceAll()

Use replaceAll() if you want to use a regular expression pattern.

Example 3

Replace any number with an x.

String myString = "__1_6____3__6_345____0";

String regex = "\\d";
String replacement = "x";

String newString = myString.replaceAll(regex, replacement); 
// __x_x____x__x_xxx____x

Example 4

Remove all whitespace.

String myString = "   Horse         Cow\n\n   \r Camel \t\t Sheep \n Goat        ";

String regex = "\\s";
String replacement = "";

String newString = myString.replaceAll(regex, replacement); 
// HorseCowCamelSheepGoat

See also

Documentation

  • replace(char oldChar, char newChar)
  • replace(CharSequence target, CharSequence replacement)
  • replaceAll(String regex, String replacement)
  • replaceFirst(String regex, String replacement)

Regular Expressions

  • Tutorial
  • List of patterns

In java.lang.String, the replace method either takes a pair of char's or a pair of CharSequence's (of which String is a subclass, so it'll happily take a pair of String's). The replace method will replace all occurrences of a char or CharSequence. On the other hand, the first String arguments of replaceFirst and replaceAll are regular expressions (regex). Using the wrong function can lead to subtle bugs.

Tags:

Java

String

Replace

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