Is there an alternative to Class.isAssignableFrom that works with Type objects?

Question

In Java, Class has an isAssignableFrom method defined as follows:

public boolean isAssignableFrom(Class<?> cls)

Determines if the class or interface represented by this Class object is either the same as, or is a superclass or superinterface of, the class or interface represented by the specified Class parameter. It returns true if so; otherwise it returns false. If this Class object represents a primitive type, this method returns true if the specified Class parameter is exactly this Class object; otherwise it returns false.

Specifically, this method tests whether the type represented by the specified Class parameter can be converted to the type represented by this Class object via an identity conversion or via a widening reference conversion. See The Java Language Specification, sections 5.1.1 and 5.1.4 , for details.

Parameters:

cls - the Class object to be checked

Returns:

the boolean value indicating whether objects of the type cls can be assigned to objects of this class

Class implements the Type interface. Is there an equivalent isAssignableFrom method that works on Types instead of just Classes? For example, is there a method that determines if a variable of type List<String> (which would be represented via an instance of ParameterizedType) can be assigned to a variable of type List<? extends Object>?

Answer 1

Have a look at javaRuntype -- I've found it useful. It can produce representations of types from instances of java.lang.reflect.Type, and test assignability between them.

Answer 2

Guava's TypeToken utility provides that functionality. Your query could be answered like this:

// represents List<String>
ParameterizedType stringList = ...; 

// represents List<? extends Object>
TypeToken objectList = new TypeToken<List<? extends Object>>(){};

boolean isAssignable = objectList.isAssignableFrom( stringList );