java.lang.reflect.Method

Again, can only obtain instances of this class through Class::getMethod().

• public Object invoke(Object obj, Object[] args) - invokes the underlying method represented by this Method object on the specified object with the specified parameters. Returns the value returned by the method (wrapped appropriately if a primitive type, null if type void).

  If there is a bad argument to invoke(), a NullPointer/ IllegalArgument/ IllegalAccessException is thrown. If the underlying method, however, throws some exception, then that exception is caught by invoke() and wrapped in an InvocationTargetException which is then thrown by invoke. Thus, to handle exceptions thrown by the underlying method, the caller must catch the InvocationTargetException and then use getTargetException() and instanceof to determine what exception it was.

• Other interesting methods: getReturnType(),getParameterTypes(), getName(), getDeclaringClass(), getExceptionTypes(),

Implementation: the class contains private variables:

    private Class               clazz;          // declaring class
    private int                 slot;           // ???
    private String              name;           // name of method
    private Class               returnType;     // ...
    private Class[]             parameterTypes;
    private Class[]             exceptionTypes;
    private int                 modifiers;

The invoke() method is native. It sets up the stack, frame, etc. and executes the method code.