设计模式课程 设计模式精讲 8-2 单例设计模式-懒汉式及多线程Deb

package com.geely.design.pattern.creational.singleton;

public class Test {

    public static void main(String [] args){
        //这样写异常，因为构造方法私有
//        LazySingleton lazySingleton = new LazySingleton();
       LazySingleton lazySingleton = LazySingleton.getInstance();
       System.out.println(lazySingleton);
    }
}

package com.geely.design.pattern.creational.singleton;

public class LazySingleton {
    /*
    属性私有，其他外部类，无法调用该属性，安全
     */
    private static LazySingleton lazySingleton = null;

    /**
     * 构造方法私有，其他类无法实例化该类
     */
    private LazySingleton(){
    }

    /**
     * 这里写静态方法：因为外部类无法实例化创建出该类，
     * 只能通过该类的静态方法获取到该类。
     * @return
     */
    public static LazySingleton getInstance(){
        if(lazySingleton == null){
            lazySingleton = new LazySingleton();
        }
        return lazySingleton;
    }
}

"C:Program FilesJavajdk1.7.0_79binjava.exe" "-javaagent:D:javadevolopKitideaanZhIntelliJ IDEA Community Edition 2018.1.4libidea_rt.jar=3988:D:javadevolopKitideaanZhIntelliJ IDEA Community Edition 2018.1.4bin" -Dfile.encoding=UTF-8 -classpath "C:Program FilesJavajdk1.7.0_79jrelibcharsets.jar;C:Program FilesJavajdk1.7.0_79jrelibdeploy.jar;C:Program FilesJavajdk1.7.0_79jrelibextaccess-bridge-64.jar;C:Program FilesJavajdk1.7.0_79jrelibextdnsns.jar;C:Program FilesJavajdk1.7.0_79jrelibextjaccess.jar;C:Program FilesJavajdk1.7.0_79jrelibextlocaledata.jar;C:Program FilesJavajdk1.7.0_79jrelibextsunec.jar;C:Program FilesJavajdk1.7.0_79jrelibextsunjce_provider.jar;C:Program FilesJavajdk1.7.0_79jrelibextsunmscapi.jar;C:Program FilesJavajdk1.7.0_79jrelibextzipfs.jar;C:Program FilesJavajdk1.7.0_79jrelibjavaws.jar;C:Program FilesJavajdk1.7.0_79jrelibjce.jar;C:Program FilesJavajdk1.7.0_79jrelibjfr.jar;C:Program FilesJavajdk1.7.0_79jrelibjfxrt.jar;C:Program FilesJavajdk1.7.0_79jrelibjsse.jar;C:Program FilesJavajdk1.7.0_79jrelibmanagement-agent.jar;C:Program FilesJavajdk1.7.0_79jrelibplugin.jar;C:Program FilesJavajdk1.7.0_79jrelibresources.jar;C:Program FilesJavajdk1.7.0_79jrelibrt.jar;F:xiangmu3XinIdeadesign_patterntargetclasses" com.geely.design.pattern.creational.singleton.Test
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Process finished with exit code 0