提交单例模式代码

Author: sgr

.gitignore

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+# Created by .ignore support plugin (hsz.mobi)
+.idea
+*.iml

pom.xml

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+<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>os.dt.design.patterns</groupId>
+ <artifactId>java-design-patterns</artifactId>
+ <packaging>pom</packaging>
+ <version>1.0-SNAPSHOT</version>
+
+ <modules>
+ <module>singleton</module>
+ </modules>
+
+ <dependencies>
+ <dependency>
+ <groupId>junit</groupId>
+ <artifactId>junit</artifactId>
+ <version>4.12</version>
+ </dependency>
+ </dependencies>
+
+
+</project>

singleton/pom.xml

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+<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">
+
+ <parent>
+ <artifactId>java-design-patterns</artifactId>
+ <groupId>os.dt.design.patterns</groupId>
+ <version>1.0-SNAPSHOT</version>
+ </parent>
+
+ <modelVersion>4.0.0</modelVersion>
+ <artifactId>singleton</artifactId>
+
+
+</project>

singleton/src/main/java/os/dt/design/patterns/singleton/HungryPresident.java

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+package os.dt.design.patterns.singleton;
+
+/**
+ * 饿汉式写法
+ * Created by songgr on 2019/10/17.
+ */
+public class HungryPresident {
+
+ private static final HungryPresident INSTANCE = new HungryPresident();
+
+ // 私有化构造方法
+ private HungryPresident(){
+
+ }
+
+ public static HungryPresident getInstance() {
+ System.out.println("getInstance");
+ return INSTANCE;
+ }
+}

singleton/src/test/java/os/dt/design/patterns/singleton/UnitTest.java

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+package os.dt.design.patterns.singleton;
+
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.TimeUnit;
+import java.util.function.Function;
+import java.util.function.Supplier;
+
+/**
+ * 测试
+ * Created by songgr on 2019/10/17.
+ */
+
+public class UnitTest {
+
+ private List<Object> objs = null;
+
+ class CreateObj implements Runnable {
+ private Object obj = null;
+
+ private Supplier function;
+ public CreateObj(Supplier function) {
+ this.function = function;
+ }
+
+ public void run() {
+ System.out.println(Thread.currentThread().getName() + ": I get a obj.");
+ Object obj = function.get();
+ objs.add(obj);
+ }
+ }
+
+ @Before
+ public void init() {
+ objs = new ArrayList<Object>(4);
+ }
+
+
+ @Test
+ public void hungryPresident() throws InterruptedException {
+ ExecutorService fixedThreadPool = Executors.newFixedThreadPool(4);
+
+ /*Supplier function = () -> HungryPresident.getInstance();
+ System.out.println(function.getClass());
+ function.get();*/
+
+ fixedThreadPool.submit(new CreateObj(() -> HungryPresident.getInstance()));
+ fixedThreadPool.submit(new CreateObj(() -> HungryPresident.getInstance()));
+ fixedThreadPool.submit(new CreateObj(() -> HungryPresident.getInstance()));
+ fixedThreadPool.submit(new CreateObj(() -> HungryPresident.getInstance()));
+
+ fixedThreadPool.awaitTermination(4, TimeUnit.SECONDS);
+
+ }
+
+ @After
+ public void check() {
+ assert objs.size() > 1;
+ objs.stream().reduce((a,b) -> a == b);
+ objs.stream().forEach(a -> System.out.println(a.getClass()));
+ }
+
+
+}