I found this type of code in a repository during my project work. That repository works well fine... but when i am trying to understand the code through an independent test run... giving error!!!
public enum Fruits {
static {
APPLE= new Fruits( "APPLE", 0 );
BANANA = new Fruits( "BANANA", 1 );
// and so on.
}
}
I am not able to understand the meaning of calling a constructor of enum inside enum, that too without declaring a constructor.
My guess is that this is actually the product of decompiling real code. This isn't valid Java source code, but is effectively what the compiler will create for you with an enum of:
public enum Fruits {
APPLE, BANANA;
}
As usual @JonSkeets's intuition wins out. Compiling the code he provided:
public enum Fruits {
APPLE, BANANA;
}
Then decompiling with jad yields:
public final class Fruits extends Enum
{
public static Fruits[] values()
{
return (Fruits[])$VALUES.clone();
}
public static Fruits valueOf(String s)
{
return (Fruits)Enum.valueOf(Fruits, s);
}
private Fruits(String s, int i)
{
super(s, i);
}
public static final Fruits APPLE;
public static final Fruits BANANA;
private static final Fruits $VALUES[];
static
{
APPLE = new Fruits("APPLE", 0);
BANANA = new Fruits("BANANA", 1);
$VALUES = (new Fruits[] {
APPLE, BANANA
});
}
}
The complete example illustrates all of the work the compiler is doing for you when you declare an enum. Note that, as @MarkoTopolnik points out, you can't do this yourself, simply because the compiler will not allow it.
public enum Fruits {
APPLE("APPLE", 0 ), BANANA("BANANA", 1 );
String text;
int value;
private Fruits(String text, int value){
this.text = text;
this.value = value;
}
public String getText(){
return text;
}
public int getValue(){
return value;
}
}
This concept is useful when you wish to add more parameters.
