Class与java反射机制

1.Class描述类信息
2.Demo:

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package cn.lee.demo;  import java.lang.reflect.Constructor;  import java.lang.reflect.Field;  import java.lang.reflect.InvocationTargetException;  import java.lang.reflect.Method;  import java.lang.reflect.Modifier;  import java.lang.reflect.TypeVariable;  public class Main {      /**      * 为了看清楚Java反射部分代码，所有异常我都最后抛出来给虚拟机处理！      * @param args      * @throws ClassNotFoundException      * @throws InstantiationException      * @throws IllegalAccessException      * @throws InvocationTargetException       * @throws IllegalArgumentException       * @throws NoSuchFieldException       * @throws SecurityException       * @throws NoSuchMethodException       */      public static void main(String[] args) throws ClassNotFoundException, InstantiationException, IllegalAccessException, IllegalArgumentException, InvocationTargetException, SecurityException, NoSuchFieldException, NoSuchMethodException {          // TODO Auto-generated method stub          //Demo1.  通过Java反射机制得到类的包名和类名          Demo1();          System.out.println("===============================================");          //Demo2.  验证所有的类都是Class类的实例对象          Demo2();          System.out.println("===============================================");          //Demo3.  通过Java反射机制，用Class 创建类对象[这也就是反射存在的意义所在]，无参构造          Demo3();          System.out.println("===============================================");          //Demo4:  通过Java反射机制得到一个类的构造函数，并实现构造带参实例对象          Demo4();          System.out.println("===============================================");          //Demo5:  通过Java反射机制操作成员变量, set 和 get          Demo5();          System.out.println("===============================================");          //Demo6: 通过Java反射机制得到类的一些属性： 继承的接口，父类，函数信息，成员信息，类型等          Demo6();          System.out.println("===============================================");          //Demo7: 通过Java反射机制调用类中方法          Demo7();          System.out.println("===============================================");          //Demo8: 通过Java反射机制获得类加载器          Demo8();          System.out.println("===============================================");      }      /**      * Demo1: 通过Java反射机制得到类的包名和类名      */      public static void Demo1()      {          Person person = new Person();          System.out.println("Demo1: 包名: " + person.getClass().getPackage().getName() + "，"                   + "完整类名: " + person.getClass().getName());      }      /**      * Demo2: 验证所有的类都是Class类的实例对象      * @throws ClassNotFoundException       */      public static void Demo2() throws ClassNotFoundException      {          //定义两个类型都未知的Class , 设置初值为null, 看看如何给它们赋值成Person类          Class<?> class1 = null;          Class<?> class2 = null;          //写法1, 可能抛出 ClassNotFoundException [多用这个写法]          class1 = Class.forName("cn.lee.demo.Person");          System.out.println("Demo2:(写法1) 包名: " + class1.getPackage().getName() + "，"                   + "完整类名: " + class1.getName());          //写法2          class2 = Person.class;          System.out.println("Demo2:(写法2) 包名: " + class2.getPackage().getName() + "，"                   + "完整类名: " + class2.getName());      }      /**      * Demo3: 通过Java反射机制，用Class 创建类对象[这也就是反射存在的意义所在]      * @throws ClassNotFoundException       * @throws IllegalAccessException       * @throws InstantiationException       */      public static void Demo3() throws ClassNotFoundException, InstantiationException, IllegalAccessException      {          Class<?> class1 = null;          class1 = Class.forName("cn.lee.demo.Person");          //由于这里不能带参数，所以你要实例化的这个类Person，一定要有无参构造函数哈～          Person person = (Person) class1.newInstance();          person.setAge(20);          person.setName("LeeFeng");          System.out.println("Demo3: " + person.getName() + " : " + person.getAge());      }      /**      * Demo4: 通过Java反射机制得到一个类的构造函数，并实现创建带参实例对象      * @throws ClassNotFoundException       * @throws InvocationTargetException       * @throws IllegalAccessException       * @throws InstantiationException       * @throws IllegalArgumentException       */      public static void Demo4() throws ClassNotFoundException, IllegalArgumentException, InstantiationException, IllegalAccessException, InvocationTargetException      {          Class<?> class1 = null;          Person person1 = null;          Person person2 = null;          class1 = Class.forName("cn.lee.demo.Person");          //得到一系列构造函数集合          Constructor<?>[] constructors = class1.getConstructors();          person1 = (Person) constructors[0].newInstance();          person1.setAge(30);          person1.setName("leeFeng");          person2 = (Person) constructors[1].newInstance(20,"leeFeng");          System.out.println("Demo4: " + person1.getName() + " : " + person1.getAge()                  + "  ,   " + person2.getName() + " : " + person2.getAge()                  );      }      /**      * Demo5: 通过Java反射机制操作成员变量, set 和 get      *       * @throws IllegalAccessException       * @throws IllegalArgumentException       * @throws NoSuchFieldException       * @throws SecurityException       * @throws InstantiationException       * @throws ClassNotFoundException       */      public static void Demo5() throws IllegalArgumentException, IllegalAccessException, SecurityException, NoSuchFieldException, InstantiationException, ClassNotFoundException      {          Class<?> class1 = null;          class1 = Class.forName("cn.lee.demo.Person");          Object obj = class1.newInstance();          Field personNameField = class1.getDeclaredField("name");          personNameField.setAccessible(true);          personNameField.set(obj, "胖虎先森");          System.out.println("Demo5: 修改属性之后得到属性变量的值：" + personNameField.get(obj));      }      /**      * Demo6: 通过Java反射机制得到类的一些属性： 继承的接口，父类，函数信息，成员信息，类型等      * @throws ClassNotFoundException       */      public static void Demo6() throws ClassNotFoundException      {          Class<?> class1 = null;          class1 = Class.forName("cn.lee.demo.SuperMan");          //取得父类名称          Class<?>  superClass = class1.getSuperclass();          System.out.println("Demo6:  SuperMan类的父类名: " + superClass.getName());          System.out.println("===============================================");          Field[] fields = class1.getDeclaredFields();          for (int i = 0; i < fields.length; i++) {              System.out.println("类中的成员: " + fields[i]);          }          System.out.println("===============================================");          //取得类方法          Method[] methods = class1.getDeclaredMethods();          for (int i = 0; i < methods.length; i++) {              System.out.println("Demo6,取得SuperMan类的方法：");              System.out.println("函数名：" + methods[i].getName());              System.out.println("函数返回类型：" + methods[i].getReturnType());              System.out.println("函数访问修饰符：" + Modifier.toString(methods[i].getModifiers()));              System.out.println("函数代码写法： " + methods[i]);          }          System.out.println("===============================================");          //取得类实现的接口,因为接口类也属于Class,所以得到接口中的方法也是一样的方法得到哈          Class<?> interfaces[] = class1.getInterfaces();          for (int i = 0; i < interfaces.length; i++) {              System.out.println("实现的接口类名: " + interfaces[i].getName() );          }      }      /**      * Demo7: 通过Java反射机制调用类方法      * @throws ClassNotFoundException       * @throws NoSuchMethodException       * @throws SecurityException       * @throws InvocationTargetException       * @throws IllegalAccessException       * @throws IllegalArgumentException       * @throws InstantiationException       */      public static void Demo7() throws ClassNotFoundException, SecurityException, NoSuchMethodException, IllegalArgumentException, IllegalAccessException, InvocationTargetException, InstantiationException      {          Class<?> class1 = null;          class1 = Class.forName("cn.lee.demo.SuperMan");          System.out.println("Demo7: \n调用无参方法fly()：");          Method method = class1.getMethod("fly");          method.invoke(class1.newInstance());          System.out.println("调用有参方法walk(int m)：");          method = class1.getMethod("walk",int.class);          method.invoke(class1.newInstance(),100);      }      /**      * Demo8: 通过Java反射机制得到类加载器信息      *       * 在java中有三种类类加载器。[这段资料网上截取]         1）Bootstrap ClassLoader 此加载器采用c++编写，一般开发中很少见。         2）Extension ClassLoader 用来进行扩展类的加载，一般对应的是jre\lib\ext目录中的类         3）AppClassLoader 加载classpath指定的类，是最常用的加载器。同时也是java中默认的加载器。      *       * @throws ClassNotFoundException       */      public static void Demo8() throws ClassNotFoundException      {          Class<?> class1 = null;          class1 = Class.forName("cn.lee.demo.SuperMan");          String nameString = class1.getClassLoader().getClass().getName();          System.out.println("Demo8: 类加载器类名: " + nameString);      }  }  /**  *   * @author xiaoyaomeng  *  */  class  Person{      private int age;      private String name;      public Person(){      }      public Person(int age, String name){          this.age = age;          this.name = name;      }      public int getAge() {          return age;      }      public void setAge(int age) {          this.age = age;      }      public String getName() {          return name;      }      public void setName(String name) {          this.name = name;      }  }  class SuperMan extends Person implements ActionInterface  {      private boolean BlueBriefs;      public void fly()      {          System.out.println("超人会飞耶～～");      }      public boolean isBlueBriefs() {          return BlueBriefs;      }      public void setBlueBriefs(boolean blueBriefs) {          BlueBriefs = blueBriefs;      }      @Override      public void walk(int m) {          // TODO Auto-generated method stub          System.out.println("超人会走耶～～走了" + m + "米就走不动了！");      }  }  interface ActionInterface{      public void walk(int m);  }