提交单例模式—饿汉模式实现代码

Singleton-Pattern/pom.xml

+<?xml version="1.0" encoding="UTF-8"?>
+
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+  <modelVersion>4.0.0</modelVersion>
+
+  <groupId>com.MrLiu.fly</groupId>
+  <artifactId>Singleton-Pattern</artifactId>
+  <version>1.0-SNAPSHOT</version>
+
+  <name>Singleton-Pattern</name>
+  <!-- FIXME change it to the project's website -->
+  <url>http://www.example.com</url>
+
+  <properties>
+    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+    <maven.compiler.source>1.7</maven.compiler.source>
+    <maven.compiler.target>1.7</maven.compiler.target>
+  </properties>
+
+  <dependencies>
+    <dependency>
+      <groupId>junit</groupId>
+      <artifactId>junit</artifactId>
+      <version>4.11</version>
+      <scope>test</scope>
+    </dependency>
+  </dependencies>
+
+  <build>
+    <pluginManagement><!-- lock down plugins versions to avoid using Maven defaults (may be moved to parent pom) -->
+      <plugins>
+        <!-- clean lifecycle, see https://maven.apache.org/ref/current/maven-core/lifecycles.html#clean_Lifecycle -->
+        <plugin>
+          <artifactId>maven-clean-plugin</artifactId>
+          <version>3.1.0</version>
+        </plugin>
+        <!-- default lifecycle, jar packaging: see https://maven.apache.org/ref/current/maven-core/default-bindings.html#Plugin_bindings_for_jar_packaging -->
+        <plugin>
+          <artifactId>maven-resources-plugin</artifactId>
+          <version>3.0.2</version>
+        </plugin>
+        <plugin>
+          <artifactId>maven-compiler-plugin</artifactId>
+          <version>3.8.0</version>
+        </plugin>
+        <plugin>
+          <artifactId>maven-surefire-plugin</artifactId>
+          <version>2.22.1</version>
+        </plugin>
+        <plugin>
+          <artifactId>maven-jar-plugin</artifactId>
+          <version>3.0.2</version>
+        </plugin>
+        <plugin>
+          <artifactId>maven-install-plugin</artifactId>
+          <version>2.5.2</version>
+        </plugin>
+        <plugin>
+          <artifactId>maven-deploy-plugin</artifactId>
+          <version>2.8.2</version>
+        </plugin>
+        <!-- site lifecycle, see https://maven.apache.org/ref/current/maven-core/lifecycles.html#site_Lifecycle -->
+        <plugin>
+          <artifactId>maven-site-plugin</artifactId>
+          <version>3.7.1</version>
+        </plugin>
+        <plugin>
+          <artifactId>maven-project-info-reports-plugin</artifactId>
+          <version>3.0.0</version>
+        </plugin>
+      </plugins>
+    </pluginManagement>
+  </build>
+</project>

Singleton-Pattern/src/main/java/com/MrLiu/fly/hungry/HungryBlockSingleton.java

+package com.MrLiu.fly.hungry;
+
+/**
+ * @author liu_l
+ * @email: liu_lei_programmer@163.com
+ * @time 2019/4/16 11:32
+ * @Description: 描述:单例—饿汉模式（在静态代码块中初始化）； 缺点：不管是否用到，都会在系统启动时实例化一个对象。
+ */
+public class HungryBlockSingleton {
+
+    private static final HungryBlockSingleton singleton;
+
+    static {
+        singleton = new HungryBlockSingleton();
+    }
+
+    private HungryBlockSingleton(){};
+
+    public static HungryBlockSingleton getInstance(){
+        return singleton;
+    }
+}

Singleton-Pattern/src/main/java/com/MrLiu/fly/hungry/HungrySingleton.java

+package com.MrLiu.fly.hungry;
+
+/**
+ * @author liu_l
+ * @email: liu_lei_programmer@163.com
+ * @time 2019/4/16 11:27
+ * @Description: 描述:单例—饿汉模式； 缺点：不管是否用到，都会在系统启动时实例化一个对象。
+ */
+public class HungrySingleton {
+    //静态字段会在类加载时进行实例化
+    private static final HungrySingleton hungrySingleton = new HungrySingleton();
+
+    //私有化构造方法
+    private HungrySingleton(){};
+
+    public static HungrySingleton getInstance(){
+        return hungrySingleton;
+    }
+}