How Java's quoted regex (\Q...\E) works.

JavaQuotedRegex.java

/*

abcxyzABCDEGPWXXYZ0(12_{@|.)+$}\/^$*!-
======A==========Z===================-
"A-Z": /[^\QA-Z\E]/

abcxyzABCDEGPWXXYZ0(12_{@|.)+$}\/^$*!-
==========================.===========
".": /[^\Q.\E]/

abcxyzABCDEGPWXXYZ0(12_{@|.)+$}\/^$*!-
==========================.========*==
".*": /[^\Q.*\E]/

abcxyzABCDEGPWXXYZ0(12_{@|.)+$}\/^$*!-
======================_===============
"_": /[^\Q_\E]/

abcxyzABCDEGPWXXYZ0(12_{@|.)+$}\/^$*!-
======ABCDEGPWXXYZ====_===============
"_": /[^A-Z\Q_\E]/

abcxyzABCDEGPWXXYZ0(12_{@|.)+$}\/^$*!-
===================(==================
"(": /[^\Q(\E]/

abcxyzABCDEGPWXXYZ0(12_{@|.)+$}\/^$*!-
======================={==============
"{": /[^\Q{\E]/

abcxyzABCDEGPWXXYZ0(12_{@|.)+$}\/^$*!-
=========================|============
"|": /[^\Q|\E]/

abcxyzABCDEGPWXXYZ0(12_{@|.)+$}\/^$*!-
==============================}=======
"}": /[^\Q}\E]/

abcxyzABCDEGPWXXYZ0(12_{@|.)+$}\/^$*!-
===========================)==========
")": /[^\Q)\E]/

abcxyzABCDEGPWXXYZ0(12_{@|.)+$}\/^$*!-
========================@=============
"@": /[^\Q@\E]/

abcxyzABCDEGPWXXYZ0(12_{@|.)+$}\/^$*!-
==============XX=====2={======}=======
"X{2}": /[^\QX{2}\E]/

abcxyzABCDEGPWXXYZ0(12_{@|.)+$}\/^$*!-
===================================*==
"*": /[^\Q*\E]/

abcxyzABCDEGPWXXYZ0(12_{@|.)+$}\/^$*!-
============================+=========
"+": /[^\Q+\E]/

abcxyzABCDEGPWXXYZ0(12_{@|.)+$}\/^$*!-
===============================\======
"\": /[^\Q\\E]/

abcxyzABCDEGPWXXYZ0(12_{@|.)+$}\/^$*!-
===============================\======
"\\": /[^\Q\\\E]/

abcxyzABCDEGPWXXYZ0(12_{@|.)+$}\/^$*!-
================================/=====
"/": /[^\Q/\E]/

abcxyzABCDEGPWXXYZ0(12_{@|.)+$}\/^$*!-
=================================^====
"^": /[^\Q^\E]/

abcxyzABCDEGPWXXYZ0(12_{@|.)+$}\/^$*!-
=============================$====$===
"$": /[^\Q$\E]/

abcxyzABCDEGPWXXYZ0(12_{@|.)+$}\/^$*!-
=b=============================\======
"\b": /[^\Q\b\E]/

abcxyzABCDEGPWXXYZ0(12_{@|.)+$}\/^$*!-
=======B=======================\======
"\B": /[^\Q\B\E]/

abcxyzABCDEGPWXXYZ0(12_{@|.)+$}\/^$*!-
======A========================\======
"\A": /[^\Q\A\E]/

abcxyzABCDEGPWXXYZ0(12_{@|.)+$}\/^$*!-
===========G===================\======
"\G": /[^\Q\G\E]/

abcxyzABCDEGPWXXYZ0(12_{@|.)+$}\/^$*!-
=====z=========================\======
"\z": /[^\Q\z\E]/

abcxyzABCDEGPWXXYZ0(12_{@|.)+$}\/^$*!-
java.util.regex.PatternSyntaxException: Illegal/unsupported escape sequence near index 3
[^\Q\E\E]
   ^
"\E": /[^\Q\E\E]/

abcxyzABCDEGPWXXYZ0(12_{@|.)+$}\/^$*!-
======A========================\======
"\A": /[^\Q\A\E]/

abcxyzABCDEGPWXXYZ0(12_{@|.)+$}\/^$*!-
========C======================\======
"\C": /[^\Q\C\E]/

abcxyzABCDEGPWXXYZ0(12_{@|.)+$}\/^$*!-
==============XX===============\======
"\X": /[^\Q\X\E]/

abcxyzABCDEGPWXXYZ0(12_{@|.)+$}\/^$*!-
================Y==============\======
"\Y": /[^\Q\Y\E]/

abcxyzABCDEGPWXXYZ0(12_{@|.)+$}\/^$*!-
=================Z=============\======
"\Z": /[^\Q\Z\E]/

abcxyzABCDEGPWXXYZ0(12_{@|.)+$}\/^$*!-
=============W=================\======
"\W": /[^\Q\W\E]/

abcxyzABCDEGPWXXYZ0(12_{@|.)+$}\/^$*!-
============P==================\======
"\P": /[^\Q\P\E]/

abcxyzABCDEGPWXXYZ0(12_{@|.)+$}\/^$*!-
=========D=====================\======
"\D": /[^\Q\D\E]/

 */

public class JavaQuotedRegex {
    private static final String base = "abcxyzABCDEGPWXXYZ0(12_{@|.)+$}\\/^$*!-";

    public static void printReplace(String characters, String pattern) {
        String regex = "[^" + pattern + "\\Q" +characters+ "\\E]";
        System.out.println(base);
        try {
            System.out.println(base.replaceAll(regex, "="));
        } catch (java.util.regex.PatternSyntaxException ex) {
            System.out.println(ex);
        }
        System.out.printf("\"%s\": /%s/\n", characters, regex);
        System.out.println("");
    }

    public static void printReplace(String characters) {
        printReplace(characters, "");
    }

    public static void main(String[] args) {
        System.out.println("");
        printReplace("A-Z");
        printReplace(".");
        printReplace(".*");
        printReplace("_");
        printReplace("_", "A-Z");
        printReplace("(");
        printReplace("{");
        printReplace("|");
        printReplace("}");
        printReplace(")");
        printReplace("@");
        printReplace("X{2}");
        printReplace("*");
        printReplace("+");
        printReplace("\\");
        printReplace("\\\\");
        printReplace("/");
        printReplace("^");
        printReplace("$");
        printReplace("\\b");
        printReplace("\\B");
        printReplace("\\A");
        printReplace("\\G");
        printReplace("\\z");
        printReplace("\\E");
        printReplace("\\A");
        printReplace("\\C");
        printReplace("\\X");
        printReplace("\\Y");
        printReplace("\\Z");
        printReplace("\\W");
        printReplace("\\P");
        printReplace("\\D");
    }
}