Difference between String replace() and replaceAll()

What's the difference between java.lang.String 's replace() and replaceAll() methods, other than later uses regex? For simple substitutions like, replace . with / , is there any difference?

Solution 1:

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.

Solution 2:

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)

Solution 3:

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