Why doesn't Class have a nice generic type in this case?

java

Solution

This problem is that Java's syntax doesn't allow getClass() to say it's returning a type which matches the class its defined in, and this is not a special case as far as the compiler is concerned. So you are forced to cast the result.

There are many cases where you would like to be able to specify `this` type, e.g. for chaining, so I would hope they include this feature one day.

You could write

Class<? extends this> getClass();

or

public this clone(); // must return a type of this class.

or

class ByteBuffer {
    this order(ByteOrder order);
}

class MappedByteBuffer extends ByteBuffer {
}

// currently this won't work as ByteBuffer defines order()
MappedByteBuffer mbb = fc.map(MapMode.READ_WRITE, 0, fc.size())
                         .order(ByteOrder.nativeOrder());

Problem

In this code, why can type not be declared as `Class<? extends B>`? ``` public class Foo<B> { public void doSomething(B argument) { Class<? extends Object> type = argument.getClass(); } } ```

Original source