JAVA学习--反射构造器操作

@Test
    public void test1() throws Exception{
        String className = "com.atguigu.java.Person";
        Class clazz = Class.forName(className);
        //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。
        //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。
        Object obj = clazz.newInstance();
        Person p = (Person)obj;
        System.out.println(p);
    }

@Test
    public void test2() throws ClassNotFoundException{
        String className = "com.atguigu.java.Person";
        Class clazz = Class.forName(className);
        
        Constructor[] cons = clazz.getDeclaredConstructors();
        for(Constructor c : cons){
            System.out.println(c);
        }
    }

//调用指定的构造器,创建运行时类的对象
    @Test
    public void test3() throws Exception{
        String className = "com.atguigu.java.Person";
        Class clazz = Class.forName(className);
        
        Constructor cons = clazz.getDeclaredConstructor(String.class,int.class);
        cons.setAccessible(true);
        Person p = (Person)cons.newInstance("罗伟",20);
        System.out.println(p);
    }

 class Person extends Creature<String> implements Comparable,MyInterface{
    public String name;
    private int age;
    int id;
    //创建类时，尽量保留一个空参的构造器。
    public Person() {
        super();
//        System.out.println("今天天气很闷热");
    }
    public Person(String name) {
        super();
        this.name = name;
    }
    private Person(String name, int age) {
        super();
        this.name = name;
        this.age = age;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }
    
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    @MyAnnotation(value = "abc123")
    public void show(){
        System.out.println("我是一个人！");
    }
    
    private Integer display(String nation,Integer i) throws Exception{
        System.out.println("我的国籍是：" + nation);
        return i;
    }
    @Override
    public String toString() {
        return "Person [name=" + name + ", age=" + age + "]";
    }
    @Override
    public int compareTo(Object o) {
        // TODO Auto-generated method stub
        return 0;
    }
    
    public static void info(){
        System.out.println("中国人！");
    }
    
    class Bird{
        
    }
    
}

import static java.lang.annotation.ElementType.CONSTRUCTOR;
import static java.lang.annotation.ElementType.FIELD;
import static java.lang.annotation.ElementType.LOCAL_VARIABLE;
import static java.lang.annotation.ElementType.METHOD;
import static java.lang.annotation.ElementType.PARAMETER;
import static java.lang.annotation.ElementType.TYPE;

import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

@Target({TYPE, FIELD, METHOD, PARAMETER, CONSTRUCTOR, LOCAL_VARIABLE})
@Retention(RetentionPolicy.RUNTIME)
public @interface MyAnnotation {
    String value();
}

public class Creature<T>{
    public double weight;
    
    public void breath(){
        System.out.println("呼吸！");
    }
}

 import java.io.Serializable; 2 3 public interface MyInterface extends Serializable{ 4 5 }