Description Ayushman Jain 2011-07-04 02:23:26 EDT

BETA_JAVA7

With Java7, some new constructs have been introduced where the type of the expression is not obvious to a reader. These are: Diamond and UnionType.

It will be good to have a feature which allows me to hover on one of these constructs and inspect the inferred type. This will help not just the reader of the code to inspect what type is being used, but also the writer to make sure that he is not accidentally using different semantics than what he intends.

For example (taken from bug 349336)

public class X<T> {
    T field1;
    public X(T param){
        field1 = param;
    }
    public static void main(String[] args) {
        X.testFunction(new X<Object>("hello").getField()); //prints 2
        X.testFunction(new X<>("hello").getField()); // prints 1
    }
    public static void testFunction(String param){
        System.out.println(1);
    }
    public static void testFunction(Object param){
        System.out.println(2);
    }
    public T getField(){
        return field1;
    }
}

the X.testFunction(new X..) method call will behave differently with and without type arguments being specified. A hover on the new X<>("hello") declaration will immediately alert the writer that the inferred type is X<String> and not X<Object>.