反射获取Person类方法、字段及调用方法演示

package _5_33;

 

import java.lang.reflect.*;

 

public class ClassDemo {

public static void main(String[] args) {

try {

Class<?> cls = Class.forName("code0508.Person");

Constructor<?> ct = cls.getConstructor(int.class);

Object obj = ct.newInstance(20); // Create an instance of Person using the constructor

 

// Get all methods of the class

Method[] methods = cls.getDeclaredMethods();

for (Method m : methods) {

System.out.print(Modifier.toString(m.getModifiers()) + " " + m.getReturnType().getName() + " " + m.getName() + "(");

Class<?>[] params = m.getParameterTypes();

for (Class<?> p : params) {

System.out.print(p.getName() + " ");

}

System.out.println(")");

}

 

// Call a specific method

Method meth = cls.getMethod("addAge", int.class);

Object retObject = meth.invoke(obj, 5); // Invoke addAge with parameter 5

System.out.println("After addAge(): " + retObject);

 

// Get all fields of the class

Field[] fields = cls.getDeclaredFields();

for (Field f : fields) {

System.out.print(Modifier.toString(f.getModifiers()) + " " + f.getType().getName() + " " + f.getName() + "; ");

}

System.out.println();

 

} catch (Exception e) {

e.printStackTrace();

}

}

}

 

class Person {

private String name;

private int age;

 

public Person() {

this.name = "default";

this.age = 0;

}

 

public Person(String name) {

this.name = name;

this.age = 0;

}

 

public Person(int age) {

this.name = "null";

this.age = age;

}

 

public String getName() {

return name;

}

 

public int getAge() {

return age;

}

 

public String toString() {

return "[" + this.name + " " + this.age + "]";

}

 

public int addAge(int a) {

return age + a;

}

}

 

class GetConstructor {

public static void main(String[] args) {

Class<?> demo = null;

try {

demo = Class.forName("code0508.Person");

} catch (Exception e) {

e.printStackTrace();

}

 

// Get all constructors

Constructor<?>[] cons = demo.getConstructors();

try {

Constructor<?> cons0 = demo.getConstructor();

Constructor<?> cons1 = demo.getConstructor(String.class);

Constructor<?> cons2 = demo.getConstructor(int.class);

Constructor<?> cons3 = demo.getConstructor(String.class, int.class);

 

Person per1 = (Person) cons0.newInstance();

Person per2 = (Person) cons1.newInstance("ZhangShan");

Person per3 = (Person) cons2.newInstance(20);

Person per4 = (Person) cons3.newInstance("Lisi", 20);

 

System.out.println(per1); // [default 0]

System.out.println(per2); // [ZhangShan 0]

System.out.println(per3); // [null 20]

System.out.println(per4); // [Lisi 20]

 

} catch (Exception e) {

e.printStackTrace();

}

}

}