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NightmaresSeller
NightmaresSeller

Reputation: 77

How to check if object implements particular interface, but not the descendants of this interface, in Java

I have a tree structure, where some nodes must contain only objects implementing particular interface. But there is interfaces extending that interface, and objects, implementing them, should not be contained in nodes.
So i need to check if object implements strictly particular interface.

public interface IProcessCell {...}
public interface IMethodCell extends IProcessCell {...}

IProcessCell processInstance = new IProcessCell() {...}
IMethodCell methodInstance = new IMethodCell() {...}

/** Method implementing desired check */
public boolean check(IProcessCell instance) {...}

Method check must return true for processInstance, but false for methodInstance

Upvotes: 1

Views: 470

Answers (4)

Jeff
Jeff

Reputation: 3707

You can do a getClass().getInterfaces() on the node, then iterate through the returned classes and check how many are assignable from the particular interface you care about. So if you have:

interface A {
}

interface B extends A {
}

class NodeA implements A {
}

class NodeB implements B {
}

If you're looking for a node instance that just implements A you should be able to do:

new NodeA().getClass().getInterfaces();
new NodeB().getClass().getInterfaces();

and in each case check that 1) One of the interfaces is A, and 2) A.class.isAssignableFrom(interface) returns false for the other returned interfaces.

Upvotes: 0

Jerry Hoerig
Jerry Hoerig

Reputation: 146

Class implements the getInterfaces() method. It returns a Class[]. Using this you could iterate and do a comparison until found or not found. http://docs.oracle.com/javase/6/docs/api/java/lang/Class.html#getInterfaces()

Upvotes: 1

Fiisch
Fiisch

Reputation: 182

You can use http://docs.oracle.com/javase/6/docs/api/java/lang/Class.html#getInterfaces()

but to me the thing you are trying to do is like patching up badly written app. To me, the better way is creating a new interface (which only desired object will implement) and making the "tree structure" nodes require that particular interface.

Upvotes: 3

Denys Séguret
Denys Séguret

Reputation: 382514

You can get the list of implemented interfaces using getInterfaces.

Assuming you already casted your instance to the desired interface, you just have to test that yourInstance.getClass().getInterfaces().length==1

Upvotes: 2

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