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Posted on In Valine:
Symbols count in article: 716 Reading time ≈ 1 mins. 
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mv /etc/apt/sources.list /etc/apt/sources.list.bak
    echo "deb http://mirrors.163.com/debian/ jessie main non-free contrib" >> /etc/apt/sources.list
    echo "deb http://mirrors.163.com/debian/ jessie-proposed-updates main non-free contrib" >>/etc/apt/sources.list
    echo "deb-src http://mirrors.163.com/debian/ jessie main non-free contrib" >>/etc/apt/sources.list
    echo "deb-src http://mirrors.163.com/debian/ jessie-proposed-updates main non-free contrib" >>/etc/apt/sources.list
    #更新安装源
    apt-get update 
    apt-get install vim

Posted on Valine:
Symbols count in article: 968 Reading time ≈ 1 mins.

内存不够，需要改配置并重启服务器

vim /etc/sysctl.conf

//在最后一行上加上

vm.max_map_count=262144

postgresql问题

fixing permissions on existing directory /var/lib/postgresql/data … ok
creating subdirectories … ok
selecting default max_connections … 100
selecting default shared_buffers … 128MB
selecting dynamic shared memory implementation … posix
creating configuration files … ok
LOG: could not link file “pg_xlog/xlogtemp.22” to “pg_xlog/000000010000000000000001”: Operation not permitted
FATAL: could not open file “pg_xlog/000000010000000000000001”: No such file or directory
child process exited with exit code 1
initdb: removing contents of data directory “/var/lib/postgresql/data”
creating template1 database in /var/lib/postgresql/data/base/1 … The files belonging to this database system will be owned by user “postgres”.
This user must also own the server process.

报错not permitted

需要在docker新建一个持久化volume

创建Volume虚拟磁盘：docker volume create –name <名称>

删除Volume虚拟磁盘：docker volume rm <名称>

  1. docker volume create *–name postgresql
  2. docker run –name mongodb -v postgresql:/data/db -p 27017:27017 -d postgresql

Posted on Valine:
Symbols count in article: 68 Reading time ≈ 1 mins.

java对于切”.”这个值要转义”\.“

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String[] split = midS.split("\\.");

Posted on In Valine:
Symbols count in article: 407 Reading time ≈ 1 mins.

简单工厂模式

image-20200606200444205

image-20200606200524558

优点

只需要传入一个正确的参数，就可以获取你所需要的对象，而无需知道其创建细节

缺点

工厂类职责相对过重，增加新的产品，需要修改工厂类的判断逻辑，违背开闭原则。、

UML

image-20200606201214011

工厂模式

工厂方法-定义和类型

定义：定义一个创建对象的接口，但让实现这个接口的类来决定实例化哪个类，工厂方法让类的实例化推迟到子类中实现。

类型：创建型。

适用场景

1.创建对象需要大量重复的代码

2.客户端（应用层）不依赖于产品类实例如何被创建，实现等细节

3.一个类通过其子类来指定创建哪个对象。

优点

1.用户只需要关心所需产品对应的工厂，无需关心创建细节。

2.加入新产品符合开闭原则，提高可扩展性。

缺点

1.类的个数容易过多，增加复杂度

2.增加了类的抽象性和理解难度

UML

image-20200606202621838

抽象工厂

image-20200606202715149

image-20200606202740380

image-20200606202758596

image-20200606202814677

工厂方法和抽象工厂

工厂方法是一个产品等级，抽象工厂是一个产品族。

比如美的空调，格力空调，松下空调是一个产品等级。

美的空调，美的洗衣机，美的冰箱，美的电饭煲则是一个产品族。

image-20200606203004204

Posted on In , Valine:
Symbols count in article: 1.8k Reading time ≈ 2 mins.

浅克隆

对于浅克隆，对象是克隆了，但是里面的类确实用的同一个，示例如下：

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/**
 * @author xixing
 * @version 1.0
 * @date 2020/6/2 19:08
 */
public class Pig implements Cloneable {


    private String name;
    private Date birthday;

    public Pig(String name, Date birthday) {
        this.name = name;
        this.birthday = birthday;
    }

    public String getName() {
        return name;
    }

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

    public Date getBirthday() {
        return birthday;
    }

    public void setBirthday(Date birthday) {
        this.birthday = birthday;
    }

    @Override
    public String toString() {
        return "Pig{" +
                "name='" + name + '\'' +
                ", birthday=" + birthday +
                '}'+super.toString();
    }

    @Override
    protected Object clone() throws CloneNotSupportedException {
        return super.clone();
    }
}
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/**
 * @author xixing
 * @version 1.0
 * @date 2020/6/2 19:12
 */
public class Test {
    public static void main(String[] args) throws CloneNotSupportedException {
        Date birthday=new Date(0);
        Pig pig1=new Pig("佩奇",birthday);
        Pig pig2= (Pig) pig1.clone();
        System.out.println(pig1);
        System.out.println(pig2);
        pig1.getBirthday().setTime(4839480394034L);
        System.out.println(pig1);
        System.out.println(pig2);

    }
}

输出

image-20200602192237120

深克隆

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@Override
protected Object clone() throws CloneNotSupportedException {
    Pig pig= (Pig) super.clone();
    //深克隆
    pig.birthday= (Date) pig.birthday.clone();
    return pig;
}

image-20200602192654029

对克隆的反射攻击破坏单例模式

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HungrySingleton hungrySingleton=HungrySingleton.getInstance();
Method method = hungrySingleton.getClass().getDeclaredMethod("clone");
method.setAccessible(true);
HungrySingleton hungrySingleton1 = (HungrySingleton) method.invoke(hungrySingleton);
System.out.println(hungrySingleton);
System.out.println(hungrySingleton1);

解决方案

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@Override
protected Object clone() throws CloneNotSupportedException {
    return getInstance();
}

或者不实现Cloneable