Java – binding generic parameters to class Uncheck when

I have some code. It uses the class name provided externally. It needs to construct an instance that implements an interface. Let's call it foo

As part of this process, I want to have the following functions:

private static Class<? extends Foo> fooFromClassName(String name) throws ClassNotFoundException {
    return (Class<? extends Foo>) Class.forName(name);
}

This clearly leads to an unchecked warning because it is indeed unsafe - the caller may have requested "Java. Lang. long" for everyone we know I finally like this method to ensure that if it does not throw, the returned class represents a foo implementation

My best solution is:

private static Class<? extends Foo> fooFromClassName(String name) throws ClassNotFoundException {
    Class<?> impl = Class.forName(name);
    if (Foo.class.isAssignableFrom(impl)) {
        @SuppressWarnings("unchecked")
        Class<? extends Foo> foo = (Class<? extends Foo>) impl;
        return foo;
    } else {
        // Throw something - ClassCastException perhaps.
    }
}

Is there a better way? Is there a way to suppress warnings indefinitely?

Solution

Class. asSubclass：

private static Class<? extends Foo> fooFromClassName(String name) throws ... {
    return Class.forName(name).asSubclass(Foo.class);
}

If the requested class is not a subclass of foo (or foo itself), you will get ClassCastException In other words, it's exactly the same as your solution