RegexTestHarness.java

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

public class RegexTestHarness {

    public static void main(String[] args){
        Console console = System.console();
        if (console == null) {
            System.err.println("No console.");
            System.exit(1);
        }
        while (true) {
            Pattern pattern = null;
            try{
                
                pattern = Pattern.compile(console.readLine("%nEnter your regex: "));


                Matcher matcher = 
                pattern.matcher(console.readLine("Enter input string to search: "));

                boolean found = false;
                while (matcher.find()) {
                    console.format("I found the text" +
                        " \"%s\" starting at " +
                        "index %d and ending at index %d.%n",
                        matcher.group(),
                        matcher.start(),
                        matcher.end());
                    found = true;
                }
                if(!found){
                    console.format("No match found.%n");
                }
            }catch (Exception ex){
                if(pattern == null){
                    console.format("Null" + pattern.toString());
                }else{
                    console.format(pattern.toString());
                }
            }
        }
    }
}