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 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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package java.lang.reflect;

/**
 * {@code InvocationHandler} is the interface implemented by
 * the <i>invocation handler</i> of a proxy instance.
 *
 * <p>Each proxy instance has an associated invocation handler.
 * When a method is invoked on a proxy instance, the method
 * invocation is encoded and dispatched to the {@code invoke}
 * method of its invocation handler.
 *
 * @author Peter Jones
 * @see Proxy
 * @since 1.3
 */
public interface InvocationHandler {

 /**
 * Processes a method invocation on a proxy instance and returns
 * the result. This method will be invoked on an invocation handler
 * when a method is invoked on a proxy instance that it is
 * associated with.
 *
 * @param proxy the proxy instance that the method was invoked on
 *
 * @param method the {@code Method} instance corresponding to
 * the interface method invoked on the proxy instance. The declaring
 * class of the {@code Method} object will be the interface that
 * the method was declared in, which may be a superinterface of the
 * proxy interface that the proxy class inherits the method through.
 *
 * @param args an array of objects containing the values of the
 * arguments passed in the method invocation on the proxy instance,
 * or {@code null} if interface method takes no arguments.
 * Arguments of primitive types are wrapped in instances of the
 * appropriate primitive wrapper class, such as
 * {@code java.lang.Integer} or {@code java.lang.Boolean}.
 *
 * @return the value to return from the method invocation on the
 * proxy instance. If the declared return type of the interface
 * method is a primitive type, then the value returned by
 * this method must be an instance of the corresponding primitive
 * wrapper class; otherwise, it must be a type assignable to the
 * declared return type. If the value returned by this method is
 * {@code null} and the interface method's return type is
 * primitive, then a {@code NullPointerException} will be
 * thrown by the method invocation on the proxy instance. If the
 * value returned by this method is otherwise not compatible with
 * the interface method's declared return type as described above,
 * a {@code ClassCastException} will be thrown by the method
 * invocation on the proxy instance.
 *
 * @throws Throwable the exception to throw from the method
 * invocation on the proxy instance. The exception's type must be
 * assignable either to any of the exception types declared in the
 * {@code throws} clause of the interface method or to the
 * unchecked exception types {@code java.lang.RuntimeException}
 * or {@code java.lang.Error}. If a checked exception is
 * thrown by this method that is not assignable to any of the
 * exception types declared in the {@code throws} clause of
 * the interface method, then an
 * {@link UndeclaredThrowableException} containing the
 * exception that was thrown by this method will be thrown by the
 * method invocation on the proxy instance.
 *
 * @see UndeclaredThrowableException
 */
 public Object invoke(Object proxy, Method method, Object[] args) throws Throwable;
}