interface TestInterface extends Callable<Void>{
    void doSomething(Future<Object> future, String id);
}

class A{
 private Future<Object> future;
 private CustomInteraface a;

 public A(Future<Object> future, CustomInteraface a){
    //do init
 }
 //getters and setters
}

Class B implements TestInterface{

    private HashMap<String, A> map = new HashMap();
    private static B monitor = new B();


    public Void call(){
        HashMap.Entry<String, A> pair = (HashMap.Entry<String, A>) it.next();
        A a = (A) pair.getValue();
        Future<Object> future = a.getFuture();
        // Do something
    }

    public void doSomething(Future<Object> future, String id){
        if(map.contains(id)){
            //Do something
        }
        else{
            A a = new A(future, null);
            map.put();
        }
    }

}

interface TestInterface extends Callable<Void>{
    <T> void doSomething(Future<T> future, String id);
}

class A<T>{
 private Future<T> future;
 private CustomInteraface a;

 public A(Future<T> future, CustomInteraface a){
    //do init
 }
 //getters and setters
}

Class B implements TestInterface{

    private HashMap<String, A> map = new HashMap();
    private static B monitor = new B();


    public Void call(){
        HashMap.Entry<String, A> pair = (HashMap.Entry<String, A>) it.next();
        A a = (A) pair.getValue();
        //Code will definitely fail here as I'm trying to cast a future object of generic type to Object class
        Future<Object> future = a.getFuture();
        // Do something
    }

    public void doSomething(Future<T> future, String id){
        if(map.contains(id)){
            //Do something
        }
        else{
            A<T> a = new A<T>(future, null);
            map.put();
        }
    }

}