Java Enum toString() method

问题:

I have several Java enums using underscores to separate words. In each of my enums I have a toString method which is implemented as super.toString().replace("_", " ") so that I can display the String values on a GUI without the underscores. Is there some way I can have all my enums use this toString method without duplicating it across all of them? If this were a regular class the answer is simple, implement toString() then have all my classes that need that implementation extend that class, but enums can't extend anything, not even another enum.

public enum Example1 {     HELLO_WORLD, HELLO_EARTH, HELLO_GLOBE     @Override public String toString() {         return super.toString().replace("_", " ");     } } public enum Example2 {     ANSWER_1, ANSWER_2, ANSWER_3     @Override public String toString() {         return super.toString().replace("_", " ");     } } 

Does anyone have a solution that doesn't duplicate this toString() method across all enums?

回答1:

public static String toString(Enum<?> enumVal) {     return String.valueOf(enumVal).replace("_", " "); } 

Usage:

String asString = toString(HELLO_WORLD); 

or,

String asString = toString(ANSWER_1); 

Typesafe approach:

public abstract class MyEnum<E extends MyEnum<E>> {      protected MyEnum(String name) {         this.name = name;     }      private String name;      protected String name() {         return name;     };      @Override     public final String toString() {         return name().replace("_", " ");     } }  public final static class Example1 extends MyEnum<Example1> {     public static final Example1 HELLO_WORLD = new Example1("HELLO_WORLD");      protected Example1(String name) {         super(name);     } } 

Usage:

System.out.println(Example1.HELLO_WORLD); 

回答2:

In Java 8 we can pull in methods using interfaces so you can now actually add functionality to enums through a form of inheritance.

public interface HasName {     public String name(); }  public interface PoliteEnum extends HasName {     default String politeName() {         return name().replace("_", " ");     } }  public enum X implements PoliteEnum {     A_For_Ism, B_For_Mutton, C_Forth_Highlanders; }  public void test() {     for (X x : X.values()) {         System.out.println(x.politeName());     } } 

prints

A For Ism B For Mutton C Forth Highlanders 

I accept that it is not as neat as overriding toString because you cannot override an Object method in the default but it certainly leaves your enum tidy.

回答3:

Declare some helper method like

public static <E extends Enum<E>> String toString(Enum<E> value) {     return value.name().replace("_", ""); // use name() as suggested in comments } 

Whenever you want to print an enum, use it

String valueToPrint = YourHelperClass.toString(Example2.ANSWER_1); 

In Java 8, you could use an interface with a default implementation which all your enums implement (but don't override).

文章来源: Java Enum toString() method