CODEWITHSUNDEEP
javagenericscallable
IUnknown
IUnknown

Reputation: 9819

A generic callable

I am trying to implement a generic callable to delegate the modification of different types of accounts. The code looks like this:

import java.util.concurrent.Callable;
class Task<T extends BaseAccount> extends Callable<T extends BaseAccount> {

  private final T t;

  public Task(T t) {
    this.t = t;
  }

  @Override
  public T call() throws Exception {
    t.increment();
    return t;
  }

}

The BaseAccount is just an abstract class as follows:

abstract class BaseAccount {
  abstract public void increment();
}

But obviously I am not getting there as I see a lot of generics-related compilation errors. Would appreciate help through this.

Upvotes: 0

Views: 7494

Answers (1)

rgettman
rgettman

Reputation: 178293

First, in a class, you don't extend an interface, you implement it. Second, you don't need to repeat that T extends BaseAccount in the Callable part. Just do this:

class task<T extends BaseAccount> implements Callable<T>

EDIT

The <T extends BaseAccount> in the task class declaration is where you have declared your generic type parameter T, so a bounds restriction is appropriate here. But implements Callable<T> is just a reference to the type parameter T, just like everywhere else in the class where you use T -- the instance variable declaration, the constructor and the method.

Additionally, it's conventional for java class names to start with a capital letter, e.g. Task, but that's not important for resolving the compiler errors.

Upvotes: 6

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