how to replace $ character?

recently I use the java.util.regex to replace a piece of string in one text? but the string contains the character of $, whatever i do,it is wrong! can you help me?

the code：

Pattern p = Pattern.compile("a\$b");

Matcher m = p.matcher(aaa$b );

bufferstring = m.replaceAll("ok");

I want to replace the "a$b" of "ok" in the String "aaa$b". how to do it ?

thanks

[423 byte] By [linugb118] at [2007-9-30 13:47:43]