String replaceAll() in java [duplicate]

Question

Can you explain the output

String str = "Total Amount is AMOUNT";
String amount = "$10.00";
str = str.replaceAll("AMOUNT", amount);
System.out.println(str);

What is the output? It throws exception

Exception in thread "main" java.lang.IndexOutOfBoundsException: No group 1

By removing $ its working.Why?

Answer 1

String.replaceAll() accepts a regex.

And $ in regex are used for replacing the captured groups. Like $1 represent's the content of first captured group... and so on.

In your case, since you don't use regex at all just use String.replace("AMOUNT", amount)

Answer 2

$is a special char in regex. You can escape it by using \\

      String amount = "\\$10.00";