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

From the question How do you find all subclasses of a given class in Java?, this answer might be helpful:

Using the class PojoClassImpl.java you can get the super class by calling method getSuperClass(). I think that is sufficient for you to write a recursive method.

Answer 2

In Java8

import java.util.Arrays;
import java.util.Optional;
import java.util.Set;
import java.util.function.Predicate;
import java.util.stream.Collectors;
import java.util.stream.Stream;

public class ClassUtil {
    public static Set<Class<?>> getAllExtendedOrImplementedTypesRecursively(final Class<?> clazz) {
        return walk(clazz)
                .filter(Predicate.isEqual(java.lang.Object.class).negate())
                .collect(Collectors.toSet());
    }

    public static Stream<Class<?>> walk(final Class<?> c) {
        return Stream.concat(Stream.of(c),
                Stream.concat(
                        Optional.ofNullable(c.getSuperclass()).map(Stream::of).orElseGet(Stream::empty),
                        Arrays.stream(c.getInterfaces())
                ).flatMap(ClassUtil::walk));
    }
}

Test Code:

import java.util.Set;

class Test {
    public static void main(String[] args) {
        final Set<Class<?>> set = ClassUtil.getAllExtendedOrImplementedTypesRecursively(Foo.class);
        set.stream().map(Class::getName).forEach(System.out::println);
    }

    class Foo extends Bar implements I1, I2 {}
    class Bar implements I3 {}
    interface I1 extends I4, I5 {}
    interface I2 {}
    interface I3 {}
    interface I4 {}
    interface I5 {}
}

Output:

Test$Foo
Test$Bar
Test$I2
Test$I5
Test$I1
Test$I3
Test$I4