CODEWITHSUNDEEP
javagenerics
Yuval Levy
Yuval Levy

Reputation: 2516

Implementing generic interface in not generic class

I want to implements a generic interface in a class. Consider implementing this generic interface:

public interface Lookup<T>{
  public T find(String name);
}

and this is the not generic class that implement Lookup:

public class IntegerLookup implements Lookup<Integer>{
  private Integer[] values;
  private String[] names;

  public IntegerLookup(String[] names, Integer[] values) {......}
  //now I want to write the implemented method - find

and my question is: how do I need to write this implemented method? I need to override it? yes?

public Object find(String name){...}

will be good? or:

public Integer find(String name){...}

Upvotes: 5

Views: 1344

Answers (2)

Sotirios Delimanolis
Sotirios Delimanolis

Reputation: 280172

The syntax here

public class IntegerLookup implements Lookup<Integer>{
//                                           ^

binds the type argument provided, ie. Integer, to the type variable declared by Lookup, ie. T.

So,

public Integer find(String name){...}

This is the same as doing

Lookup<Integer> lookup = ...;
lookup.find("something"); // has a return type of Integer

Upvotes: 3

Judge Mental
Judge Mental

Reputation: 5239

From your comments it sounds like you really want to use Object as the return type. I can't imagine why you would want to do that, but if so, you actually need to implement Lookup< Object >, not Lookup< Integer >.

But don't do that. Use Integer as the return type, since that type is standing in for T in your implementation.

Upvotes: 0

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