java - StringIndexOutOfBoundsException on replaceAll using lookahead and backslash? -

i'd escape quotes (single , double) , backslashes of string.

i'm trying single call of mystring.replaceall. regex match , replace (?=['\"\\\\]) (escaped java syntax), or more readable: (?=['!\]) (unescaped syntax). i'm doing lookahead, because want keep quotes , backslashes, , insert escape character before each of them.

if use + escape character, works charm (all strings below in escaped java syntax):

"abc'def\"ghi\\jkl".replaceall("(?=['\"\\\\])", "+") results in "abc+'def+\"ghi+\\jkl". yay!

however, if use backslash escape character, i'm getting stringindexoutofboundsexception instead: string index out of range: 1.

the call looks this: "abc'def\"ghi\\jkl".replaceall("(?=['\"\\\\])", "\\\\")

that's odd... inserted backslash interfere somehow backslash within lookahead regex? if so, how can avoid behavior?

here full testing code:

import static org.junit.assert.assertequals; import static org.junit.assert.assertfalse; import static org.junit.assert.asserttrue; import org.junit.test;  public class regextest {     @test public void test() {         assertequals("abc\\'def\\\"ghi\\\\jkl", "abc'def\"ghi\\jkl".replaceall("(?=['\"\\\\])", "\\\\"));     } } 

any appreciated!