Accessible object literals in Java

Global.java

public class Global {
  public static Undefined undefined = Undefined.getInstance();
}

ObjectLiteral.java

import java.lang.reflect.*;

public class ObjectLiteral {
  public Object apply(String key) {
    Class cls = this.getClass();
    try {
      Field fld = cls.getField(key);
      return fld.get(this);
    } catch (Exception e) {
      return Global.undefined;
    }
  }

  @Override
  public String toString() {
    Class cls = this.getClass();
    StringBuilder sb = new StringBuilder();
    sb.append('{');

    Field[] flds = cls.getDeclaredFields();
    int length = flds.length;

    int i = 0;
    for (Field fld : flds) {
      String key = fld.getName();
      Object value = this.apply(key);

      sb.append(key + ": ");
      sb.append(value);
      
      if (++i < length)
        sb.append(", ");
      else
        sb.append('}');
    }

    return sb.toString();
  }
}

ObjLiteralsTest.java

public class ObjLiteralsTest {
  public static void main(String[] args) {
    ObjectLiteral user = new ObjectLiteral() {
      public int    id   = 1;
      public String name = "pvorb";
    };

    // will print "{id: 1, name: pvorb}"
    System.out.println(user);
  }
}

Undefined.java

public class Undefined {
  private static Undefined instance = null;

  private Undefined() {
  }

  public static Undefined getInstance() {
    if (instance == null)
      instance = new Undefined();
    return instance;
  }
}