Finding most specific overloaded method using MethodHandle

Question

Suppose I have three methods inside a given type (class/interface):

public void foo(Integer integer);
public void foo(Number number);
public void foo(Object          


        

Answer 1

Given the constraints that: a) the type of the parameter is only known at runtime, and b) there is only one parameter, a simple solution can be just walking up the class hierarchy and scanning the implemented interfaces like in the following example.

public class FindBestMethodMatch {

    public Method bestMatch(Object obj) throws SecurityException, NoSuchMethodException {
        Class superClss = obj.getClass();
        // First look for an exact match or a match in a superclass
        while(!superClss.getName().equals("java.lang.Object")) {
            try {
                return getClass().getMethod("foo", superClss);          
            } catch (NoSuchMethodException e) {
                superClss = superClss.getSuperclass();
            }
        }
        // Next look for a match in an implemented interface
        for (Class intrface : obj.getClass().getInterfaces()) {
            try {
                return getClass().getMethod("foo", intrface);
            } catch (NoSuchMethodException e) { }           
        }
        // Last pick the method receiving Object as parameter if exists
        try {
            return getClass().getMethod("foo", Object.class);
        } catch (NoSuchMethodException e) { }

        throw new NoSuchMethodException("Method not found");
    }

    // Candidate methods

    public void foo(Map map) { System.out.println("executed Map"); } 

    public void foo(Integer integer) { System.out.println("executed Integer"); } 

    public void foo(BigDecimal number) { System.out.println("executed BigDecimal"); }

    public void foo(Number number) { System.out.println("executed Number"); }

    public void foo(Object object) { System.out.println("executed Object"); }

    // Test if it works
    public static void main(String[] args) throws SecurityException, NoSuchMethodException, IllegalArgumentException, IllegalAccessException, InvocationTargetException {
        FindBestMethodMatch t = new FindBestMethodMatch();
        Object param = new Long(0);
        Method m = t.bestMatch(param);
        System.out.println("matched " + m.getParameterTypes()[0].getName());
        m.invoke(t, param);
        param = new HashMap();
        m = t.bestMatch(param);
        m.invoke(t, param);
        System.out.println("matched " + m.getParameterTypes()[0].getName());
    }

}