/**
*
* The Method Class is used to describe the methods in the Class: Method getMethod (String name, Class ... ParameterTypes)
* This Class object is returned to indicate the specified public Method of the Class and its parent Class. Method [] getMethods ():
* This Class object is returned to indicate all public methods of the Class and its parent Class. Method getDeclaredMethod (String name,
* Class ... ParameterTypes) returns the Class object that represents the specified method of the Class. It has nothing to do with access permissions, but does not include inherited methods. Method []
* GetDeclaredMethods (): obtains all methods of the class, including public, protected, default (Package) Access, and private methods, but not inherited methods;
*
*
*
*/
Package cn.com. java. wwh. www;
Import java. lang. reflect. Array;
Import java. lang. reflect. Method;
Import java. util. ArrayList;
Import java. util. List;
/**
* @ Class: used to call the reflection method.
*
*
* @ Author
* @ Version 1.0
* @ Creation Time: 4:11:32
*
*/
Class Person {
Public void sayHello1 (){
System. out. println (hello !);
}
Public static String sayHello2 (){
Return a boat;
}
Private String sayHello3 (String name, int age ){
System. out. println (name + ----> + age );
Return name + age;
}
// Use generic processing
Public List sayHello4 (String name, int age ){
List list = new ArrayList ();
List. add (name );
List. add (age );
Return list;
}
Public String [] sayHello5 (String name, int age ){
Return new String [] {name, age + };
}
}
Public class ReflectDemo {
Public static void main (String [] args) throws Exception {
// Call the sayHello method in Person Using Reflection
/**
* 1. Get the bytecode of the Class where the method is located. -----> Class Object
* 2. Get the sayHello Method; -------> Method object
* 3. Execute the Method (sayHello );
*/
// Obtain the class bytecode
Class Claz = Person. class;
Method meth = claz. getMethod (sayHello2 );
/**
* Object invoke (Object obj, Object... args) calls this Method for a specified Object with a specified parameter.
* Underlying method of object representation.
*
* Parameter: obj-indicates the object to which the underlying method belongs. Here, sayHello is the underlying method, and obj should be an object of the class where sayHello is located; args
*-Actual parameters required for calling the underlying method: access the execution result of the underlying method;
*
*
* If the underlying method is static, you can ignore the specified obj parameter. This parameter can be null.
*/
Object obj = meth. invoke (claz. newInstance (); // both static and non-static
Object obj1 = meth. invoke (null); // static
System. out. println (obj1 );
Meth = claz. getDeclaredMethod (sayHello3, String. class, int. class );
System. out. println (meth );
// You can set it to accessible before calling
Meth. setAccessible (true );
// Input parameters
Object obj2 = meth. invoke (claz. newInstance (), Fujian Normal University, 22 );
System. out. println (obj2 );
// Use generic processing
Method meth2 = claz. getMethod (sayHello4, String. class, int. class );
Object obj3 = meth2.invoke (claz. newInstance (), fl, 30 );
System. out. println (obj3 );
List list = (List) obj3;
System. out. println (obj3 );
System. out. println (list. get (0 ));
// Method exercise 5
// This method must be public; otherwise, an exception occurs during the call.
Method meth5 = claz. getMethod (sayHello5, String. class, int. class );
Object obj5 = meth5.invoke (claz. newInstance (), no regrets, 22 );
String [] array = (String []) obj5;
System. out. println (meth5 );
System. out. println (array [0]);
/**
* Array: static Object get (Object array, int index) returns the index value of the specified Array Object.
*
* Static int getLength (Object array) returns the length of the specified array Object in the form of an int.
*
*
* Static void set (Object array, int index, Object value)
* Set the value of the index component in the specified array object to the specified new value.
*/
Array. set (array, 0, haha );
Array. set (array, 1, 18 );
// System. out. println (Array. get (array, 0 ));
// System. out. println (Array. get (array, 1 ));
// Obtain the length of the array
Int number = Array. getLength (array );
System. out. println (the length of the array is: + number );
For (int I = 0; I <number; I ++ ){
System. out. println (Array. get (array, I ));
}
// Method without Parameters
// If the shape parameter required by the underlying method is 0, the length of the provided args array can be 0 or null.
Method me = claz. getMethod (sayHello1 );
Me. invoke (claz. newInstance (); // correct
Me. invoke (claz. newInstance (), null); // correct
Me. invoke (claz. newInstance (), new Object [] {}); // correct
Method met = claz. getDeclaredMethod (sayHello3, String. class, int. class );
// Set accessible
Met. setAccessible (true );
Met. invoke (claz. newInstance (), flat boat & no regrets, 22 );
Met. invoke (claz. newInstance (), Yiyepianzhou, 22 );
Met. invoke (claz. newInstance (), new Object [] {ha, 20 });
}
}
