Java basics - Enum

An enum type is a special data type that enables for a variable to be a set of predefined constants.
An enum is static by default. There is an Enum class too, read about the differences here.

The simplest use case

public enum Status {
 TODO, DOING, DONE
}

Properties and more

The enum values can have properties assigned. The type may contain other methods that calculate using the values. It may also contain a main method.
Note: If the values have properties, these conditions must be fulfilled:

• Semicolon after the last value declaration
• A field for each property
• Required arguments constructor

public enum Status {
 TODO(0, "A"), 
 DOING(1, "B"), 
 DONE(2, "C");
 
 private final int code;
 private final String variant;
 
 private Status(int code, String variant) {
  this.code = code;
  this.variant = variant;
 }

 public int getCode() {
  return code;
 }

 public String getVariant() {
  return variant;
 }
}

EnumMap

It is recommended to use EnumMap if the key is enum. The syntax to create one is:

Map<Status, Integer> map = new EnumMap<Status, Integer>(Status.class);

Then it can be used like any map with put and get.