Java Reflection: How to know if a Method is static?

Question

I want to discover at run-time ONLY the static Methods of a class, how can I do this? Or, how to differentiate between static and non-static methods.

Answer 1

Use Modifier.isStatic(method.getModifiers()).

/**
 * Returns the public static methods of a class or interface,
 *   including those declared in super classes and interfaces.
 */
public static List<Method> getStaticMethods(Class<?> clazz) {
    List<Method> methods = new ArrayList<Method>();
    for (Method method : clazz.getMethods()) {
        if (Modifier.isStatic(method.getModifiers())) {
            methods.add(method);
        }
    }
    return Collections.unmodifiableList(methods);
}

Note: This method is actually dangerous from a security standpoint. Class.getMethods "bypass[es] SecurityManager checks depending on the immediate caller's class loader" (see section 6 of the Java secure coding guidelines).

Disclaimer: Not tested or even compiler.

Note Modifier should be used with care. Flags represented as ints are not type safe. A common mistake is to test a modifier flag on a type of reflection object that it does not apply to. It may be the case that a flag in the same position is set to denote some other information.

Answer 2

To flesh out the previous (correct) answer, here is a full code snippet which does what you want (exceptions ignored):

public Method[] getStatics(Class<?> c) {
    Method[] all = c.getDeclaredMethods()
    List<Method> back = new ArrayList<Method>();

    for (Method m : all) {
        if (Modifiers.isStatic(m.getModifiers())) {
            back.add(m);
        }
    }

    return back.toArray(new Method[back.size()]);
}

Answer 3

You can get the static methods like this:

for (Method m : MyClass.class.getMethods()) {
   if (Modifier.isStatic(m.getModifiers()))
      System.out.println("Static Method: " + m.getName());
}