import java.util.regex.Matcher;
import java.util.regex.Pattern;
import java.util.*;
import java.lang.*;
import java.io.*;
 
class Ideone
{
	public static void main (String[] args) throws java.lang.Exception
	{
		String regex = "^([^_]+)_([^_]+)_";
		String string = "02_01_fEa3129E_my Pic.png";
		String subst = "$1/$2/";
 
		Pattern pattern = Pattern.compile(regex);
		Matcher matcher = pattern.matcher(string);
		String result = matcher.replaceFirst(subst);
 
		System.out.println(result);
	}
}

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