Java总结篇系列：Java 反射

            
                  1
                package
                 com.corn;

                  2
                  3
                import
                 java.lang.reflect.Constructor;

                  4
                import
                 java.lang.reflect.Field;

                  5
                import
                 java.lang.reflect.InvocationTargetException;

                  6
                import
                 java.lang.reflect.Method;

                  7
                  8
                public
                class
                 TestReflect {

                  9
                 10
                public
                static
                void
                 main(String[] args) {

                 11
                 12
                //
                 获取“类类型对象”  方法1
                 13         Class<?> c0 = User.class;
 14 15// 获取“类类型对象”  方法2 16         User user1 = new User();
 17         Class<?> c1 = user1.getClass();
 18 19         User user2 = new User();
 20         Class<?> c2 = user2.getClass();
 21 22         System.out.println("user class instance 0:" + c0); //user class instance 0:class com.corn.User 23         System.out.println("user class instance 1:" + c1); //user class instance 1:class com.corn.User 24         System.out.println("user class instance 2:" + c2); //user class instance 2:class com.corn.User
 25 26//c0 == c1 :true, c1 == c2 :true 27         System.out.println("c0 == c1 :" + (c0 == c1) + ", c1 == c2 :" + (c1 == c2));
 28 29try {
 30// 获取“类类型对象”  方法3 31             Class<?> c3 = Class.forName("com.corn.User");
 32             System.out.println("user class c3:" + c3); //user class c3:class com.corn.User 33 34try {
 35                 User user3 = (User) c3.newInstance();
 36 37//Constructor public com.corn.User(int,java.lang.String,int)
 38//Constructor public com.corn.User(int,java.lang.String)
 39//Constructor public com.corn.User() 40                 Constructor<?>[] cons = c3.getConstructors();
 41for (int i = 0; i < cons.length; i++) {
 42// 一次返回类定义中所有public修饰符修饰的“构造器对象”,其与类定义中的构造器顺序不一定相同 43                     System.out.println("Constructor " + cons[i]);
 44                }
 45 46try {
 47                     User user4 = (User) cons[1].newInstance(51, "corn");
 48//user instance 4:user instance uid:51 name:corn 49                     System.out.println("user instance 4:" + user4);
 50 51// 返回特定参数类型的“构造器对象”所新建的实例 52                    User user40;
 53                     user40 = (User) c3.getConstructor(int.class, String.class).newInstance(520, "corn0");
 54//user instance 40:user instance uid:520 name:corn0 55                     System.out.println("user instance 40:" + user40);
 56 57// 返回该类“类类型对象”的所有的父类“类类型对象” 58                     Class<?> father = c3.getSuperclass();
 59//father class instance class com.corn.Person 60                     System.out.println("father class instance " + father);
 61 62//返回类对象所有的接口对象（其实也是类类型对象）数组 63                     Class<?>[] interfaceArray = c3.getInterfaces();
 64//interface class instance 0 interface com.corn.Workable
 65//interface class instance 1 interface com.corn.Thinkable 66for (int i = 0; i < interfaceArray.length; i++) {
 67// 与implements中接口顺序相同 68                         System.out.println("interface class instance " + i + " " + interfaceArray[i]);
 69                    }
 70 71                 } catch (IllegalArgumentException e) {
 72                    e.printStackTrace();
 73                 } catch (InvocationTargetException e) {
 74                    e.printStackTrace();
 75                }
 76 77             } catch (InstantiationException e) {
 78                e.printStackTrace();
 79             } catch (IllegalAccessException e) {
 80                e.printStackTrace();
 81            }
 82         } catch (ClassNotFoundException e) {
 83            e.printStackTrace();
 84         } catch (Exception e) {
 85            e.printStackTrace();
 86        }
 87 88// 返回“类类型对象”所具有的全部属性实例/对象 89         Field[] fieldArray = c0.getDeclaredFields();
 90//filed 0 private int com.corn.User.uid
 91//filed 1 private java.lang.String com.corn.User.name
 92//filed 2 private int com.corn.User.age 93for (int i = 0; i < fieldArray.length; i++) {
 94             System.out.println("filed " + i + " " + fieldArray[i]);
 95        }
 96 97         User u = new User(12, "yumidi", 99);
 98 99try {
100// 直接获取private/私有属性的值101             Field nameField = c0.getDeclaredField("name");
102//取消Java对访问修饰符的检查   103             nameField.setAccessible(true);
104             String nameValue = (String) nameField.get(u);
105//name:yumidi106             System.out.println("name:" + nameValue);
107108// 直接改变private/私有属性的值109             nameField.set(u, "corn");
110//new name:corn111             System.out.println("new name:" + u.getName());
112113         } catch (NoSuchFieldException e) {
114            e.printStackTrace();
115         } catch (SecurityException e) {
116            e.printStackTrace();
117         } catch (Exception e) {
118            e.printStackTrace();
119        }
120121//访问私有方法122try {
123             Method method = c0.getDeclaredMethod("getResult");
124//取消Java对访问修饰符的检查125             method.setAccessible(true);
126int result = (int) method.invoke(u);
127//result:1000128             System.out.println("result:" + result);
129130         } catch (NoSuchMethodException e) {
131            e.printStackTrace();
132         } catch (SecurityException e) {
133            e.printStackTrace();
134         } catch (Exception e) {
135            e.printStackTrace();
136        }
137138    }
139}
140141class User extends Person implements Workable, Thinkable {
142143privateint uid;
144private String name;
145privateint age;
146147public User() {
148149    }
150151private User(int uid) {
152this.uid = uid;
153    }
154155protected User(String name) {
156this.name = name;
157    }
158159public User(int uid, String name) {
160this.uid = uid;
161this.name = name;
162    }
163164public User(int uid, String name, int age) {
165this.uid = uid;
166this.name = name;
167this.age = age;
168    }
169170publicint getUid() {
171return uid;
172    }
173174publicvoid setUid(int uid) {
175this.uid = uid;
176    }
177178public String getName() {
179return name;
180    }
181182publicvoid setName(String name) {
183this.name = name;
184    }
185186publicint getAge() {
187return age;
188    }
189190publicvoid setAge(int age) {
191this.age = age;
192    }
193194privateint getResult() {
195return 1000;
196    }
197198    @Override
199public String toString() {
200return "user instance uid:" + this.uid + " name:" + this.name;
201    }
202203}
204205class Person {
206207}
208209interface Workable {
210211}
212213interface Thinkable {
214215 }