java regex to match variable

Question

I have the name of a java variable in a string. I want to replace it with the letter x. How can I do this java, and make sure that other words in the string are not replaced ?

For example, say my variable is res, and my string is "res = res + pres + resd + _res. I want the string to become x = x + pres + resd + _res.

assylias · Accepted Answer · 2013-05-30 11:19:29Z

1

You can use a word boundary to only capture whole words:

String s = "res = res + pres + resd + _res";
String var = "res";
System.out.println(s.replaceAll("\\b" + var + "\\b", "x"));

outputs x = x + pres + resd + _res

answered May 30, 2013 at 11:19

assylias

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4 Comments

Car981 Over a year ago

I really want any correct way to create a variable (as allowed by the language itself) to be taken into account. I added _res in my original post to reflect this example. "res=res+pres" should also work, even though there are no spaces

assylias Over a year ago

@Car981 The code I propose will work with _res or res=res+pres too.

Car981 Over a year ago

Okay, will it also work with dollar signs, numbers, and basically anything that is given here: docs.oracle.com/javase/tutorial/java/nutsandbolts/… ?

assylias Over a year ago

@Car981 Yes it should - note that the list of valid characters provided in that link is far from exhaustive.

Andrzej Doyle · Accepted Answer · 2013-05-30 11:21:52Z

0

You can use the \b metacharacter to match a word boundary. (Bear in mind you'll need to use doule backslashes to escape this in Java.)

So you can do something like the following:

final String searchVar = "res";
final String replacement = "x";
final String in = "res = res + pres + resd + _res";

final String result = in.replaceAll("\\b" + searchVar + "\\b", replacement);
System.out.println(result);
// prints "x = x + pres + resd + _res"

answered May 30, 2013 at 11:21

Andrzej Doyle

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