JAVA学习--反射构造器操作

             1
            @Test

             2
            public
            void
             test1() throws Exception{

             3         String className = "com.atguigu.java.Person";
 4         Class clazz = Class.forName(className);
 5//创建对应的运行时类的对象。使用newInstance()，实际上就是调用了运行时类的空参的构造器。
 6//要想能够创建成功：①要求对应的运行时类要有空参的构造器。②构造器的权限修饰符的权限要足够。 7         Object obj = clazz.newInstance();
 8         Person p = (Person)obj;
 9         System.out.println(p);
10     }

             1
            @Test

             2
            public
            void
             test2() throws ClassNotFoundException{

             3         String className = "com.atguigu.java.Person";
 4         Class clazz = Class.forName(className);
 5 6         Constructor[] cons = clazz.getDeclaredConstructors();
 7for(Constructor c : cons){
 8             System.out.println(c);
 9        }
10     }

             1
            //
            调用指定的构造器,创建运行时类的对象
             2
                @Test

             3
            public
            void
             test3() throws Exception{

             4         String className = "com.atguigu.java.Person";
 5         Class clazz = Class.forName(className);
 6 7         Constructor cons = clazz.getDeclaredConstructor(String.class,int.class);
 8         cons.setAccessible(true);
 9         Person p = (Person)cons.newInstance("罗伟",20);
10         System.out.println(p);
11     }

             1
            class Person extends Creature<String> implements Comparable,MyInterface{
 2public String name;
 3privateint age;
 4int id;
 5//创建类时，尽量保留一个空参的构造器。 6public Person() {
 7        super();
 8//        System.out.println("今天天气很闷热"); 9    }
10public Person(String name) {
11        super();
12this.name = name;
13    }
14private Person(String name, int age) {
15        super();
16this.name = name;
17this.age = age;
18    }
19public String getName() {
20return name;
21    }
22publicvoid setName(String name) {
23this.name = name;
24    }
25publicint getAge() {
26return age;
27    }
28publicvoid setAge(int age) {
29this.age = age;
30    }
3132publicint getId() {
33return id;
34    }
35publicvoid setId(int id) {
36this.id = id;
37    }
38     @MyAnnotation(value = "abc123")
39publicvoid show(){
40         System.out.println("我是一个人！");
41    }
4243private Integer display(String nation,Integer i) throws Exception{
44         System.out.println("我的国籍是：" + nation);
45return i;
46    }
47    @Override
48public String toString() {
49return"Person [name=" + name + ", age=" + age + "]";
50    }
51    @Override
52publicint compareTo(Object o) {
53// TODO Auto-generated method stub54return0;
55    }
5657publicstaticvoid info(){
58         System.out.println("中国人！");
59    }
6061class Bird{
6263    }
6465 }

             1 import static java.lang.annotation.ElementType.CONSTRUCTOR;
 2 import static java.lang.annotation.ElementType.FIELD;
 3 import static java.lang.annotation.ElementType.LOCAL_VARIABLE;
 4 import static java.lang.annotation.ElementType.METHOD;
 5 import static java.lang.annotation.ElementType.PARAMETER;
 6 import static java.lang.annotation.ElementType.TYPE;
 7 8import java.lang.annotation.Retention;
 9import java.lang.annotation.RetentionPolicy;
10import java.lang.annotation.Target;
1112@Target({TYPE, FIELD, METHOD, PARAMETER, CONSTRUCTOR, LOCAL_VARIABLE})
13@Retention(RetentionPolicy.RUNTIME)
14public @interface MyAnnotation {
15    String value();
16 }

            1
            public
            class Creature<T>{
2publicdouble weight;
34publicvoid breath(){
5         System.out.println("呼吸！");
6    }
7 }