Question

I have a complete Java based code base, where members are named:

String m_sFoo;
Array m_arrKeepThings;

Variable/object names includes both a m_ prefix to indicate a member, and an hungarian notation type indicator.

I’m looking for a way to perform a single time code replacment to (for example on the above to cases):

Array keepThings;
String foo;

Of course there are many other alternatives, but I hope that based on two examples, I’ll be able to perform the full change.
Performances is not an issue as it’s a single time fix.

To clarify, if I had to explain this in lines, it would be:

1. Match words starting with m_[a-zA-Z].
2. After m_, drop whatever is there before the first Capital letter.
3. Change the first capital letter to lower case.

Answer 1

Here is some Java code that works. It is not pure regex, but based on:

Usage:

String str = "String m_sFoo;\n"
        + "Array m_arrKeepThings;\n"
        + "List<? extends Reader> m_lstReaders; // A silly comment\n"
        + "String.format(\"Hello World!\"); /* No m_named vars here */";
// Read the file you want to handle instead

NameMatcher nm = new NameMatcher(str);
System.out.println(nm.performReplacements());

NameMatcher.java

package so_6806699;

import java.util.regex.Matcher;
import java.util.regex.Pattern;

/**
 *
 * @author martijn
 */
public class NameMatcher
{

    private String input;
    public static final String REGEX = "m_[a-z]+([A-Z0-9_\\$\\µ\\£]*)";
    public static final Pattern PATTERN = Pattern.compile(REGEX);

    public NameMatcher(String input)
    {
        this.input = input;
    }

    public String performReplacements()
    {
        Matcher m = PATTERN.matcher(input);
        StringBuilder sb = new StringBuilder();

        int oldEnd = 0;
        while (m.find())
        {
            int start = m.start();
            int end = m.end();

            String match = input.substring(start, end);
            String matchGroup1 = match.replaceAll(REGEX, "$1");
            if (!matchGroup1.isEmpty())
            {
                char[] match_array = matchGroup1.toCharArray();
                match_array[0] = Character.toLowerCase(match_array[0]);
                match = new String(match_array);
            }

            sb.append(input.substring(oldEnd, start));
            oldEnd = end;

            sb.append(match);
        }
        sb.append(input.substring(oldEnd));
        return sb.toString();
    }
}

Demo Output:

String foo;
Array keepThings;
List<? extends Reader> readers; // A silly comment
String.format("Hello World!"); /* No m_named vars here */

Edit 0:
Since dollar signs ($), micro (µ) and pound (£) are valid characters for Java name variables, I edited the regex.

Edit 1: It seems that there are a lot of non-latin characters that are valid (éùàçè, etc). Hopefully you don’t have to handle them.

Edit 2: I’m only a human being! So be aware of errors there might be in the code! Make a BACKUP first!

Edit 3: Code improved. A NPE was thrown when the code contains this: m_foo. These will be unhandled.