find all classes and interfaces a class extends or implements recursively

Question

I was wondering if there was an easy way of determining the complete list of Types that a Java class extends or implements recursively?

for instance:

cla         


        

Answer 1

The following implementation of the method does what the OP requires, it traverses the inheritance hierarchy for every class and interface:

public static Set> getAllExtendedOrImplementedTypesRecursively(Class clazz) {
    List> res = new ArrayList<>();

    do {
        res.add(clazz);

        // First, add all the interfaces implemented by this class
        Class[] interfaces = clazz.getInterfaces();
        if (interfaces.length > 0) {
            res.addAll(Arrays.asList(interfaces));

            for (Class interfaze : interfaces) {
                res.addAll(getAllExtendedOrImplementedTypesRecursively(interfaze));
            }
        }

        // Add the super class
        Class superClass = clazz.getSuperclass();

        // Interfaces does not have java,lang.Object as superclass, they have null, so break the cycle and return
        if (superClass == null) {
            break;
        }

        // Now inspect the superclass 
        clazz = superClass;
    } while (!"java.lang.Object".equals(clazz.getCanonicalName()));

    return new HashSet>(res);
}    

I tested with JFrame.class and I got the following:

Set> classes = getAllExtendedOrImplementedTypesRecursively(JFrame.class);
for (Class clazz : classes) {
    System.out.println(clazz.getName());
}

Output:

java.awt.Container
java.awt.Frame
javax.swing.JFrame
javax.swing.TransferHandler$HasGetTransferHandler
java.awt.Window
javax.accessibility.Accessible
javax.swing.RootPaneContainer
java.awt.Component
javax.swing.WindowConstants
java.io.Serializable
java.awt.MenuContainer
java.awt.image.ImageObserver

UPDATE: For the OP's test case it prints:

test.I5
test.Bar
test.I2
test.I1
test.Foo
test.I3
test.I4