Remove comments from a source code in java

Anand :

I want to remove all type of comments statements from a java source code file. Example:

    String str1 = "SUM 10"      /*This is a Comments */ ;   
    String str2 = "SUM 10";     //This is a Comments"  
    String str3 = "http://google.com";   /*This is a Comments*/
    String str4 = "('file:///xghsghsh.html/')";  //Comments
    String str5 = "{\"temperature\": {\"type\"}}";  //comments

Expected Output:

    String str1 = "SUM 10"; 
    String str2 = "SUM 10";  
    String str3 = "http://google.com";
    String str4 = "('file:///xghsghsh.html/')";
    String str5 = "{\"temperature\": {\"type\"}}";

I am using the below regular expression to achieve :

    System.out.println(str1.replaceAll("[^:]//.*|/\\\\*((?!=*/)(?s:.))+\\\\*/", ""));

This gives me wrong result for str4 and str5. Please help me to resolve this issue.

Using Andreas solutions:

        final String regex = "//.*|/\\*(?s:.*?)\\*/|(\"(?:(?<!\\\\)(?:\\\\\\\\)*\\\\\"|[^\\r\\n\"])*\")";
        final String string = "    String str1 = \"SUM 10\"      /*This is a Comments */ ;   \n"
             + "    String str2 = \"SUM 10\";     //This is a Comments\"  \n"
             + "    String str3 = \"http://google.com\";   /*This is a Comments*/\n"
             + "    String str4 = \"('file:///xghsghsh.html/')\";  //Comments\n"
             + "    String str5 = \"{\"temperature\": {\"type\"}}";  //comments";
        final String subst = "$1";

        // The substituted value will be contained in the result variable
        final String result = string.replaceAll(regex,subst);

        System.out.println("Substitution result: " + result);

Its working except str5.

Andreas :

To make it work, you need to "skip" string literals. You can do that by matching string literals, capturing them so they can be retained.

The following regex will do that, using $1 as the substitution string:

//.*|/\*(?s:.*?)\*/|("(?:(?<!\\)(?:\\\\)*\\"|[^\r\n"])*")

See regex101 for demo.

Java code is then:

str1.replaceAll("//.*|/\\*(?s:.*?)\\*/|(\"(?:(?<!\\\\)(?:\\\\\\\\)*\\\\\"|[^\r\n\"])*\")", "$1")

Explanation

//.*                      Match // and rest of line
|                        or
/\*(?s:.*?)\*/            Match /* and */, with any characters in-between, incl. linebreaks
|                        or
("                        Start capture group and match "
  (?:                      Start repeating group:
     (?<!\\)(?:\\\\)*\\"     Match escaped " optionally prefixed by escaped \'s
     |                      or
     [^\r\n"]                Match any character except " and linebreak
  )*                       End of repeating group
")                        Match terminating ", and end of capture group

$1                        Keep captured string literal