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2 changes: 1 addition & 1 deletion PART_1_算法基础/README.md
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## PART I 算法基础
## PART_1_算法基础

[下载 XMIND 完整版](https://www.cxyhub.com/all/programming/12460/)

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2 changes: 1 addition & 1 deletion PART_2_力扣图解/README.md
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## PART II 算法图解题典
## PART_2_力扣图解

| Title | 分类 | 难度 |
|---|---|---|
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13 changes: 13 additions & 0 deletions PART_3_大厂面试/README.md
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## PART_3_大厂面试

考虑到现在网上面经实在太杂，很多都冠以 “BAT” 之名，重复率、错误率都非常高。所以我尽可能的挑选出了我认为比较好的 50 篇面经（基本不重复），并对内容做了分类。

建议大家把这个页面收藏起来，防止后面需要的时候找不到了。

希望大家可以点个 star 支持一下~

- [系统设计-长文（非常建议读，我自己也看了）](https://github.com/donnemartin/system-design-primer/blob/master/README-zh-Hans.md)
- [后端-社招(两年): 蚂蚁 头条 PingCAP](https://github.com/aylei/interview)
- [后端-京东-JAVA](https://www.cnblogs.com/wupeixuan/p/8908524.html#%E4%B8%80%E3%80%81java)
- [后端-百度-高并发抢红包设计](https://github.com/xbox1994/Java-Interview/blob/master/MD/%E7%B3%BB%E7%BB%9F%E8%AE%BE%E8%AE%A1-%E9%AB%98%E5%B9%B6%E5%8F%91%E6%8A%A2%E7%BA%A2%E5%8C%85.md)
- [NLP（机器学习）-百度](https://www.e-learn.cn/topic/95743)
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82 changes: 82 additions & 0 deletions hello-algorithm.iml
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185 changes: 185 additions & 0 deletions other/designpattern/中介者模式.md
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## 中介者（Mediator）

### 介绍

中介者模式（Mediator Pattern）是用来降低多个对象和类之间的通信复杂性。这种模式提供了一个中介类，该类通常处理不同类之间的通信，并支持松耦合，使代码易于维护。中介者模式属于行为型模式。

### Intent

集中相关对象之间复杂的沟通和控制方式。

### Class Diagram

- Mediator：中介者，定义一个接口用于与各同事（Colleague）对象通信。
- Colleague：同事，相关对象

<div align="center"> <img src="https://cs-notes-1256109796.cos.ap-guangzhou.myqcloud.com/30d6e95c-2e3c-4d32-bf4f-68128a70bc05.png"/> </div><br>

### Implementation

Alarm（闹钟）、CoffeePot（咖啡壶）、Calendar（日历）、Sprinkler（喷头）是一组相关的对象，在某个对象的事件产生时需要去操作其它对象，形成了下面这种依赖结构：

<div align="center"> <img src="https://cs-notes-1256109796.cos.ap-guangzhou.myqcloud.com/82cfda3b-b53b-4c89-9fdb-26dd2db0cd02.jpg"/> </div><br>

使用中介者模式可以将复杂的依赖结构变成星形结构：

<div align="center"> <img src="https://cs-notes-1256109796.cos.ap-guangzhou.myqcloud.com/5359cbf5-5a79-4874-9b17-f23c53c2cb80.jpg"/> </div><br>

```java
public abstract class Colleague {
public abstract void onEvent(Mediator mediator);
}
```

```java
public class Alarm extends Colleague {

@Override
public void onEvent(Mediator mediator) {
mediator.doEvent("alarm");
}

public void doAlarm() {
System.out.println("doAlarm()");
}
}
```

```java
public class CoffeePot extends Colleague {
@Override
public void onEvent(Mediator mediator) {
mediator.doEvent("coffeePot");
}

public void doCoffeePot() {
System.out.println("doCoffeePot()");
}
}
```

```java
public class Calender extends Colleague {
@Override
public void onEvent(Mediator mediator) {
mediator.doEvent("calender");
}

public void doCalender() {
System.out.println("doCalender()");
}
}
```

```java
public class Sprinkler extends Colleague {
@Override
public void onEvent(Mediator mediator) {
mediator.doEvent("sprinkler");
}

public void doSprinkler() {
System.out.println("doSprinkler()");
}
}
```

```java
public abstract class Mediator {
public abstract void doEvent(String eventType);
}
```

```java
public class ConcreteMediator extends Mediator {
private Alarm alarm;
private CoffeePot coffeePot;
private Calender calender;
private Sprinkler sprinkler;

public ConcreteMediator(Alarm alarm, CoffeePot coffeePot, Calender calender, Sprinkler sprinkler) {
this.alarm = alarm;
this.coffeePot = coffeePot;
this.calender = calender;
this.sprinkler = sprinkler;
}

@Override
public void doEvent(String eventType) {
switch (eventType) {
case "alarm":
doAlarmEvent();
break;
case "coffeePot":
doCoffeePotEvent();
break;
case "calender":
doCalenderEvent();
break;
default:
doSprinklerEvent();
}
}

public void doAlarmEvent() {
alarm.doAlarm();
coffeePot.doCoffeePot();
calender.doCalender();
sprinkler.doSprinkler();
}

public void doCoffeePotEvent() {
// ...
}

public void doCalenderEvent() {
// ...
}

public void doSprinklerEvent() {
// ...
}
}
```

```java
public class Client {
public static void main(String[] args) {
Alarm alarm = new Alarm();
CoffeePot coffeePot = new CoffeePot();
Calender calender = new Calender();
Sprinkler sprinkler = new Sprinkler();
Mediator mediator = new ConcreteMediator(alarm, coffeePot, calender, sprinkler);
// 闹钟事件到达，调用中介者就可以操作相关对象
alarm.onEvent(mediator);
}
}
```

```java
doAlarm()
doCoffeePot()
doCalender()
doSprinkler()
```

### JDK

- All scheduleXXX() methods of [java.util.Timer](http://docs.oracle.com/javase/8/docs/api/java/util/Timer.html)
- [java.util.concurrent.Executor#execute()](http://docs.oracle.com/javase/8/docs/api/java/util/concurrent/Executor.html#execute-java.lang.Runnable-)
- submit() and invokeXXX() methods of [java.util.concurrent.ExecutorService](http://docs.oracle.com/javase/8/docs/api/java/util/concurrent/ExecutorService.html)
- scheduleXXX() methods of [java.util.concurrent.ScheduledExecutorService](http://docs.oracle.com/javase/8/docs/api/java/util/concurrent/ScheduledExecutorService.html)
- [java.lang.reflect.Method#invoke()](http://docs.oracle.com/javase/8/docs/api/java/lang/reflect/Method.html#invoke-java.lang.Object-java.lang.Object...-)

你可以通过下方扫码回复【进群】，加入我们的高端计算机学习群！以及下载超过 100 张高清思维导图！

<div align="center">
<a href="https://www.geekxh.com/code.png" style="box-shadow: rgb(210, 210, 210) 0em 0em 0.5em 0px; font-size: 17px;"><img src="https://www.geekxh.com/code.png" width="250px"></a>
</div>







102 changes: 102 additions & 0 deletions other/designpattern/享元模式.md
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## 享元（Flyweight）

### 介绍

享元模式（Flyweight Pattern）主要用于减少创建对象的数量，以减少内存占用和提高性能。这种类型的设计模式属于结构型模式，它提供了减少对象数量从而改善应用所需的对象结构的方式。

享元模式尝试重用现有的同类对象，如果未找到匹配的对象，则创建新对象。我们将通过创建 5 个对象来画出 20 个分布于不同位置的圆来演示这种模式。由于只有 5 种可用的颜色，所以 color 属性被用来检查现有的 Circle 对象。

### Intent

利用共享的方式来支持大量细粒度的对象，这些对象一部分内部状态是相同的。

### Class Diagram

- Flyweight：享元对象
- IntrinsicState：内部状态，享元对象共享内部状态
- ExtrinsicState：外部状态，每个享元对象的外部状态不同

<div align="center"> <img src="https://cs-notes-1256109796.cos.ap-guangzhou.myqcloud.com/5f5c22d5-9c0e-49e1-b5b0-6cc7032724d4.png"/> </div><br>

### Implementation

```java
public interface Flyweight {
void doOperation(String extrinsicState);
}
```

```java
public class ConcreteFlyweight implements Flyweight {

private String intrinsicState;

public ConcreteFlyweight(String intrinsicState) {
this.intrinsicState = intrinsicState;
}

@Override
public void doOperation(String extrinsicState) {
System.out.println("Object address: " + System.identityHashCode(this));
System.out.println("IntrinsicState: " + intrinsicState);
System.out.println("ExtrinsicState: " + extrinsicState);
}
}
```

```java
public class FlyweightFactory {

private HashMap<String, Flyweight> flyweights = new HashMap<>();

Flyweight getFlyweight(String intrinsicState) {
if (!flyweights.containsKey(intrinsicState)) {
Flyweight flyweight = new ConcreteFlyweight(intrinsicState);
flyweights.put(intrinsicState, flyweight);
}
return flyweights.get(intrinsicState);
}
}
```

```java
public class Client {

public static void main(String[] args) {
FlyweightFactory factory = new FlyweightFactory();
Flyweight flyweight1 = factory.getFlyweight("aa");
Flyweight flyweight2 = factory.getFlyweight("aa");
flyweight1.doOperation("x");
flyweight2.doOperation("y");
}
}
```

```html
Object address: 1163157884
IntrinsicState: aa
ExtrinsicState: x
Object address: 1163157884
IntrinsicState: aa
ExtrinsicState: y
```

### JDK

Java 利用缓存来加速大量小对象的访问时间。

- java.lang.Integer#valueOf(int)
- java.lang.Boolean#valueOf(boolean)
- java.lang.Byte#valueOf(byte)
- java.lang.Character#valueOf(char)

你可以通过下方扫码回复【进群】，加入我们的高端计算机学习群！以及下载超过 100 张高清思维导图！

<div align="center">
<a href="https://www.geekxh.com/code.png" style="box-shadow: rgb(210, 210, 210) 0em 0em 0.5em 0px; font-size: 17px;"><img src="https://www.geekxh.com/code.png" width="250px"></a>
</div>





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