Implement Interface with Generic Java

Question

I can't call string methods on element and argument. The UML diagram tells me that StartsWith class has a Generic TypeT>String. I read in an other post you need to implement it in this way <T extends String>. I would like to substitute Object for T in the method here public boolean predicate(Object element, Object argument) but the compiler throws at me thats not possible.

interface:

public interface Intaf<T> {

    public boolean pres(T element, T argument);
}

class:

public class StartsWith <T extends String> implements Intaf {

    @Override
    public boolean pres(Object element, Object argument) {

        String firstLetterElement = element.substring(0,1);

        String firstLetterArgument = argument.substring(0,1);

        return firstLetterElement.equals(firstLetterArgument);
    }
}

Joe C · Accepted Answer · 2018-07-15 14:00:23Z

1

You want to implement Intaf<T>. Just saying Intaf implies Intaf<Object>.

answered Jul 15, 2018 at 14:00

Joe C

15.8k8 gold badges42 silver badges52 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

flyingfox · Accepted Answer · 2018-07-15 14:01:28Z

0

Change to

public class StartsWith <T extends String> implements Intaf<T> {

    @Override
    public boolean pres(T element, T argument) {

        String firstLetterElement = element.substring(0,1);

        String firstLetterArgument = argument.substring(0,1);

        return firstLetterElement.equals(firstLetterArgument);
    }
}

answered Jul 15, 2018 at 14:01

flyingfox

13.5k4 gold badges30 silver badges43 bronze badges

1 Comment

Johannes Kuhn Over a year ago

String is final. So T can only have the type of String.

Thiyagu · Accepted Answer · 2018-07-15 14:01:08Z

0

You need to change as Intaf<T> and change the arguments as type T

@Override
public boolean pres(T element, T argument) {
 ....
}

answered Jul 15, 2018 at 14:01

Thiyagu

18k5 gold badges49 silver badges88 bronze badges

Collectives™ on Stack Overflow

Implement Interface with Generic Java

3 Answers 3

Comments

1 Comment

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

1 Comment

Comments

Your Answer

Sign up or log in

Post as a guest

Related