java param access other param

[David Spades]

package com.whatever;

public enum MyEnum {
	
	INSTANCE1(A.class);
	
	private Class<?> fieldType;
	
	MyEnum(MyEnumClass<?> fieldType){
		this.fieldType = fieldType;
	}

}

and other method that takes this enum as param

public void myMethod(MyEnum myEnum, ??? xxx){}

in this method, I'd like to do type checking based on myEnum passed as the first param. the second param must be of same type as myEnum.fieldType.
How do I get this to work?
thanks

[Darryl Burke]

David Spades wrote:

	private Class<?> fieldType;
	
	MyEnum(MyEnumClass<?> fieldType){
		this.fieldType = fieldType;
	}

Does that even compile?

[Paul Clapham]

David Spades wrote:in this method, I'd like to do type checking based on myEnum passed as the first param. the second param must be of same type as myEnum.fieldType.
How do I get this to work?

If you want the compiler to check the type of the second parameter, then the type of myEnum.fieldType must be known at compile time. Your posted code is a bit off (as per what Darryl said) and your example with only one enum member isn't sufficient, I don't think, but I doubt you're going to get it to work. But if you'd like to work on your example a bit, perhaps something can be done.

[David Spades]

public enum MyEnum {
     
    INSTANCE1(A.class), INSTANCE2(B.class), INSTANCE3(C.class);
     
    private Class<?> fieldType;
     
    MyEnum(Class<?> fieldType){
        this.fieldType = fieldType;
    }
 
}

sorry, typo in the code, it should've been like this.

[Darryl Burke]

You can receive your second parameter as Object obj and test obj.getClass() == myEnum.getFieldType(). Or if it needn't be the exact same class, you can leverage Class#isAssignableFrom(...) or isInstance(...).

[David Spades]

yes, I already know about that, but that would be runtime check, no compile time check. I forgot to mention that I want to achieve compile-time checking.

so something like

public void myMethod(MyEnum myEnum, Class<? extends myEnum.fieldType> type){}

thanks

[Rob Spoor]

Not possible, because the type is only known at runtime. During compile time the compiler isn't smart enough to see whether an A, B or C is required.