Unsafe

首先unsafe 是不可以被实例化的，是内部的api 不允许外部直接调用

可能在以后的版本会被删除

如何创建一个unsafe类

通过反射进行创建一个类

try {
    Constructor constructor = Unsafe.class.getDeclaredConstructor();
    constructor.setAccessible(true);
    Unsafe unsafe = (Unsafe) constructor.newInstance();
    myUnsafe.unsafe = unsafe;
}  catch (NoSuchMethodException e) {
    e.printStackTrace();
} catch (InvocationTargetException | InstantiationException | IllegalAccessException e) {
    throw new RuntimeException(e);
}

无视构造函数构造类

使用unsafe.allocateInstance

假设一下的类不能被创建了

package fun.au9u5t;

import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectOutputStream;
import java.io.Serializable;

public class User  implements Serializable
{
    public String name;
    private int age;

    public User(String name, int age) {
        this.name = name;
        this.age = age;
    }
    public User(int age){
        this.age = age;
    }

    public void Say(){
        System.out.println(this.name+": My name is " + name + " and I am " + age + " years old.");
    }

    private void Say(String message ){
        System.out.println(this.name+": "+message);
    }

    public void setName(String name){
        this.name = name;
    }

    public String ToString(){
        return this.name+": My name is " + name + " and I am " + age + " years old.";
    }

//    public static void main(String[] args) {
//        User user = new User("august",99);
//        // 序列化成文件
//        String fileName= "user.ser";
//        try (ObjectOutputStream oos=  new ObjectOutputStream(new FileOutputStream(fileName))){
//            oos.writeObject(user);
//        }catch (IOException e){
//            e.printStackTrace();
//        }
//    }
}

尝试直接创建对象

User user=(User) unsafe.allocateInstance(User.class);