我应该如何转换具有多个边界的 Java 泛型? [英] How should I cast for Java generic with multiple bounds?

问题描述

Is it possible to cast an object in Java to a combined generic type?

I have a method like:

public static <T extends Foo & Bar> void doSomething(T object) {
    //do stuff
}

Calling this method is no problem if I have a class that implements both interfaces (Foo & Bar).

The problem is when I need to call this method the object I need to pass to it is received as java.lang.Object and I need to cast it to make the compiler happy. But I can't figure out how to make this cast.

edit:

The problem lies in a function like this:

public void problemFunction (Object o) {
  if ( o instanceof Foo && o instanceof Bar) {
      doSomething((Problematic cast) o);
  }
}

}

解决方案

Java 8 introduces the possibility of casting with additional bounds. You can cast an Object as a class with multiple interfaces (or just as multiple interfaces).

So this:

doSomething((Problematic cast) o);

simply becomes to this:

doSomething((Foo & Bar) o);

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