反射构造方法，用构造方法实例化对象

反射构造方法，用构造方法实例化对象：

测试代码：

package reflect;

import java.lang.reflect.Constructor;

public class Test15 {
    public static void main(String[] args) throws Exception {

        // 不使用反射机制创建对象
        Student15 s1 = new Student15();
        Student15 s2 = new Student15(1001, "张三", "2020-7-27", true);
        System.out.println(s1);  // Student15{no=0, name='null', birth='null', sex=false}
        System.out.println(s2);  // Student15{no=1001, name='张三', birth='2020-7-27', sex=true}

        // 使用反射机制创建对象
        // 反射获取一个类
        Class theClass = Class.forName("reflect.Student15");

        // 获取无参数构造方法
        Constructor c1 = theClass.getDeclaredConstructor();

        // 获取有参数构造方法
        Constructor c2 = theClass.getDeclaredConstructor(int.class, String.class, String.class, boolean.class);

        // 无参数构造方法实例化对象
        Object obj1 = theClass.newInstance();
        Object obj2 = c1.newInstance();
        System.out.println(obj1);  // Student15{no=0, name='null', birth='null', sex=false}
        System.out.println(obj2);  // Student15{no=0, name='null', birth='null', sex=false}

        // 有参数构造方法实例化对象
        Object obj3 = c2.newInstance(1002, "李四", "2020-7-27", false);
        System.out.println(obj3);  // Student15{no=1002, name='李四', birth='2020-7-27', sex=false}
    }
}

class Student15 {
    int no;
    String name;
    String birth;
    boolean sex;

    public Student15() {

    }

    public Student15(int no, String name, String birth, boolean sex) {
        this.no = no;
        this.name = name;
        this.birth = birth;
        this.sex = sex;
    }

    @Override
    public String toString() {
        return "Student15{" + "no=" + no + ", name='" + name + '\'' +
                ", birth='" + birth + '\'' + ", sex=" + sex + '}';
    }
}