Multiple type Implementations using same interface variable

Question

Suppose I have an interface:

interface MyInterface <T>;

then suppose I have multiple implementations

public class Imp1 implements MyInterface<Object>
public class Imp2 implements MyInterface<Object2>

Can I reuse same interface variable without specifying a type?

so say,

MyInterface var1 = new Imp1();
var1 = new Imp2();

oppose to having to do this:

MyInterface var1<?> = new Imp1();

Or must I always do that/live with that warning?

Here is what I need.

I am using selenium for test automation.

I have an interface that is a table. Which represents a html table for getting rows. Next I have type methods that return the equivalent pojo object. For example a cars table will return a cars object. One table could be used on many pages, and each different page could return a different pojo object.

What is the purpose of reusing this variable? To confuse code reviewer? — Alex Salauyou
– Alex Salauyou, Commented May 7, 2015 at 20:35
Ok, I see, but if you don't know particular type in compilation time (if POJO is car or tractor or smth else), you cannot avoid the need to remember class of POJO and use it as argument in methods that process it (e.g. in switch statement where you'll cast it to particular class). — Alex Salauyou
– Alex Salauyou, Commented May 7, 2015 at 20:44

Luiggi Mendoza · Accepted Answer · 2015-05-07 20:31:53Z

1

For your case, you can declare the variables like this:

MyInterface<Object> var1 = new Imp1();
MyInterface<Object2> var2 = new Imp2();

And there's no need to deal wth the warning at all.

If you want/need to use it without providing the generic type, this is, using the interface with raw type, then you have to live with the warning.

Anyway, you can supress the warning by using @SupressWarnings like this.

@SupressWarnings("rawtypes")
void foo() {
    MyInterface var1 = new Imp1();
}

answered May 7, 2015 at 20:31

Luiggi Mendoza

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