Enum Constant Implicit Methods

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∟Enum Constant Implicit Methods

This section describes 2 static methods implicitly added by the Java compiler to all enum types declared by the 'enum' statement.

When you define an enum type with an "enum" declaration statement, the Java compiler implicitly adds two static method in the resulting class.

1. "public static E valueOf(String name)" - Returning the enum constant of this enum type with the specified name. This method is equivalent to the "public static E valueOf(Class<E> enumType, String name)" static method defined in the base class java.lang.Enum<E>.

2. "public static E[] values() " - Returning an array of this enum type containing all enum constants declared in this enum type.

Note that those implicit methods are not mentioned in JDK API documentation. You have to read the Java language specification to find them.

Here is a sample program that shows you how to invoke methods listed above:

/* EnumImplicitMethods.java
 * Copyright (c) HerongYang.com. All Rights Reserved.
 */
import java.lang.Enum;
class EnumImplicitMethods {
   enum Rank { GOLD, SILVER, BRONZE; }
   public static void main(String[] arg) {
      java.io.PrintStream out = System.out;
      out.println("Enum type implicit static methods:");
      out.println("   Rank.valueOf() = "+Rank.valueOf("GOLD"));
      out.println("   Rank.values() =");
      for (Rank r : Rank.values()) out.println("      "+r);
   }
}

If you compile and run EnumImplicitMethods.java, you should get:

herong> java EnumImplicitMethods.java

Enum type implicit static methods:
   Rank.valueOf() = GOLD
   Rank.values() =
      GOLD
      SILVER
      BRONZE