How to use Java reflection when the enum type is a Class?

Question

I was using an enum in which the constant was a Class. I needed to invoke a method on the constant but could not introduce a compile time dependency and the enum was not always available at runtime (part of optional install). Therefore, I wanted to use reflection.

This is easy, but I hadn't used reflection with enums before.

The enum looked something like this:

public enum PropertyEnum {    SYSTEM_PROPERTY_ONE("property.one.name", "property.one.value"),    SYSTEM_PROPERTY_TWO("property.two.name", "property.two.value");    private String name;      private String defaultValue;    PropertyEnum(String name) {     this.name = name;   }    PropertyEnum(String name, String value) {     this.name = name;     this.defaultValue = value;   }     public String getName() {     return name;   }    public String getValue() {     return System.getProperty(name);   }    public String getDefaultValue() {     return defaultValue;   }    } 

What is an example of invoking a method of the constant using reflection?

Answer 1

import java.lang.reflect.Method;  class EnumReflection {    public static void main(String[] args)     throws Exception   {     Class<?> clz = Class.forName("test.PropertyEnum");     /* Use method added in Java 1.5. */     Object[] consts = clz.getEnumConstants();     /* Enum constants are in order of declaration. */     Class<?> sub = consts[0].getClass();     Method mth = sub.getDeclaredMethod("getDefaultValue");     String val = (String) mth.invoke(consts[0]);     /* Prove it worked. */     System.out.println("getDefaultValue " +        val.equals(PropertyEnum.SYSTEM_PROPERTY_ONE.getDefaultValue()));   }  }