Question

I understand I can create an enum like this:

public enum MyEnum {
   ONE(1),
   TWO(2);
   private int value;
   private MyEnum(int value) {
      this.value = value);
   }
   public int getValue() {
      return value;
   }
}

But I have some questions:

1) It seems that the enum values are declared at the start. Is there a particular format for this. Could I declare them anywhere?

2) Is is possible to declare an enum with more than one constructor and is this something that people sometimes do?

Answer 1

public enum MyEnum {
   ONE(1),
   TWO(1, 2);
   private int value1, value2;

   private MyEnum(int value) {
      this.value1 = value;
      this.value2 = 0; // default
      // this.value2 = getFromSomewhereElse(); // get it at runtime
   }

   private MyEnum(int value1, int value2) {
      this.value1 = value1;
      this.value2 = value2;
   }

   public int getValue1() {
      return this.value1;
   }

   public int getValue2() {
      return this.value2;
   }
}

1. Yes, you must declare the enum values at the start. Always.
2. See code above. It is possible. If people do it depends on the application. If you have a lot of fields and most of them should be a default value, it is a good thing to use multiple constructors. Also, the values for the fields could be read at runtime (from a file or another static class).