反射构造方法，用构造方法实例化对象

亦凉 2023-03-01 13:49 94阅读 0赞

#### 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 + '}';
        }
    }

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