Program that prints Java system properties; can be run interactively

SysPropsTool.java

import java.util.Properties;
import java.util.Scanner;
 
public class SysPropsTool {
  public static final String QUIT = "/Q";
  public static final String QUIT_ = "/QUIT";
  public static final String HELP = "/?";
  public static final String HELP_ = "/H";
  public static final String HELP__ = "/HELP";
  public static final String LIST = "/LS";
  public static final String LIST_ = "/LIST";
  public static final String LISTALL = "/ALL";
  public static final String PROPS = "props >>>";
  static Properties props = System.getProperties();

  public static void main (String[] args) {
    if (args.length > 0) {
      for (String arg : args) {
        String preStic = arg.trim().toUpperCase();
        if (!react(preStic, arg)) {
          System.exit(0);
        }
      }
    } else {
      usageInfo();
      Scanner sc = new Scanner(System.in);
      while (true) {
        System.out.print(PROPS);
        try {
          String line = sc.nextLine();
          if (line == null || line.length() < 1) {
            continue;
          }
          String preStic = line.trim().toUpperCase();
          boolean keepGoing = react(preStic, line);
          if (!keepGoing) {
            break;
          }

        } catch (Exception ex) {
          System.err.println(ex.toString());
          usageInfo();
        }
    }
   }  
  }
  
  static boolean react(String preStic, String line) {
        if (QUIT.equals(preStic) || QUIT_.equals(preStic)) {
          return false;
        }
         
        if (HELP.equals(preStic) || HELP_.equals(preStic) || HELP__.equals(preStic)) {
          usageInfo();
          return true;
        }
         
        boolean isList = LIST.equals(preStic) || LIST_.equals(preStic) || LISTALL.equals(preStic);
        if (isList) {
          showAll();
        }else {
          showIndivl(line);
        }
        return true;
  }
 
  static void showAll () {
    if (props != null) {
      props.list(System.out);
    }
  }
   
  static void showIndivl (String key) {
    String value = props.getProperty(key, "[NAN]");
    StringBuilder info = new StringBuilder(key);
    info.append("=").append(value);
     
    System.out.println(info);
  }
   
  public static String get (String key) {
    return props.getProperty(key);
  }
   
  public static Properties set (String key, String value) {
    props.setProperty(key, value);
    return props;
  }
   
  static void usageInfo () {
    System.out.println("[Usage]: \n\t [/q|/quit]:\t to quit \n\t [/ls|/list|/all]:\t to list all props \n\t {key}:\t get the key-value \n\t [/h|/?|/help]:\t for help");
  }
}

I didn't write the original version of this, but I have no idea where it came from. The original version only ran in interactive mode, and I added a feature where the user specifies a command or property name on the command line and the program reacts to it in the way it would have in interactive mode, then exits.