单例模式之饿汉模式

饿汗模式就是不管你需不需要我就就是先创建出来，给你提供一个方法，你需要的时候自己获取就可以了
构造器必须私有化，确保只有这一个实例
饿汗模式：

public class SimpleHungry {
    private static final SimpleHungry instance = new SimpleHungry();
    private SimpleHungry(){

    }
    public static SimpleHungry getInstance(){
        return instance;
    }
}

测试类：

public class Test {
    public static void main(String[] args) {
        SimpleHungry simpleHungry = SimpleHungry.getInstance();
        System.out.println(simpleHungry);
    }
}

执行结果：

E:\Java\jdk\bin\java.exe "-javaagent:E:\IntelliJ IDEA 2018.2.4\lib\idea_rt.jar=62915:E:\IntelliJ IDEA 2018.2.4\bin" -Dfile.encoding=UTF-8 -classpath E:\Java\jdk\jre\lib\charsets.jar;E:\Java\jdk\jre\lib\deploy.jar;E:\Java\jdk\jre\lib\ext\access-bridge-64.jar;E:\Java\jdk\jre\lib\ext\cldrdata.jar;E:\Java\jdk\jre\lib\ext\dnsns.jar;E:\Java\jdk\jre\lib\ext\jaccess.jar;E:\Java\jdk\jre\lib\ext\jfxrt.jar;E:\Java\jdk\jre\lib\ext\localedata.jar;E:\Java\jdk\jre\lib\ext\nashorn.jar;E:\Java\jdk\jre\lib\ext\sunec.jar;E:\Java\jdk\jre\lib\ext\sunjce_provider.jar;E:\Java\jdk\jre\lib\ext\sunmscapi.jar;E:\Java\jdk\jre\lib\ext\sunpkcs11.jar;E:\Java\jdk\jre\lib\ext\zipfs.jar;E:\Java\jdk\jre\lib\javaws.jar;E:\Java\jdk\jre\lib\jce.jar;E:\Java\jdk\jre\lib\jfr.jar;E:\Java\jdk\jre\lib\jfxswt.jar;E:\Java\jdk\jre\lib\jsse.jar;E:\Java\jdk\jre\lib\management-agent.jar;E:\Java\jdk\jre\lib\plugin.jar;E:\Java\jdk\jre\lib\resources.jar;E:\Java\jdk\jre\lib\rt.jar;F:\IdeaProjects\simple\out\production\simple hungry.Test
hungry.SimpleHungry@1b6d3586