{"id":1111,"date":"2023-03-12T13:28:51","date_gmt":"2023-03-12T05:28:51","guid":{"rendered":"https:\/\/www.appblog.cn\/?p=1111"},"modified":"2023-04-29T11:23:32","modified_gmt":"2023-04-29T03:23:32","slug":"design-pattern-singleton-pattern","status":"publish","type":"post","link":"https:\/\/www.appblog.cn\/index.php\/2023\/03\/12\/design-pattern-singleton-pattern\/","title":{"rendered":"\u8bbe\u8ba1\u6a21\u5f0f\uff082\uff09\u5355\u4f8b\u6a21\u5f0f"},"content":{"rendered":"

\u5355\u4f8b\u6a21\u5f0f\u7684\u4f5c\u7528\u662f\u786e\u4fdd\u67d0\u4e2a\u7c7b\u53ea\u6709\u4e00\u4e2a\u5b9e\u4f8b\uff0c\u907f\u514d\u4ea7\u751f\u591a\u4e2a\u5bf9\u8c61\u6d88\u8017\u8fc7\u591a\u7684\u8d44\u6e90\u3002\u6bd4\u5982\u5bf9\u6570\u636e\u5e93\u7684\u64cd\u4f5c\u65f6\uff0c\u5c31\u53ef\u4ee5\u4f7f\u7528\u5355\u4f8b\u6a21\u5f0f\u3002<\/p>\n

<\/p>\n

\u5355\u4f8b\u5b9e\u73b0<\/h2>\n

\u997f\u6c49\u6a21\u5f0f<\/h3>\n

\u8fd9\u79cd\u5199\u6cd5\u662f\u5728\u7c7b\u88c5\u8f7d\u65f6\u5c31\u5b9e\u4f8b\u5316instance\uff0c\u4ed6\u907f\u514d\u4e86\u591a\u7ebf\u7a0b\u7684\u540c\u6b65\u95ee\u9898\u3002\u4f46\u662f\u4e0d\u80fd\u4fdd\u8bc1\u6709\u522b\u7684\u65b9\u5f0f\u53bb\u88c5\u8f7d\uff0c\u6ca1\u6709\u8fbe\u5230\u61d2\u52a0\u8f7d\u3002<\/p>\n

public class Singleton {\n    private static Singleton instance = new Singleton();\n    private Singleton () {\n    }\n    public static Singleton getInstance() {\n    return instance;\n    }\n}<\/code><\/pre>\n
\u61d2\u6c49\u6a21\u5f0f\uff08\u7ebf\u7a0b\u4e0d\u5b89\u5168\uff09<\/h3>\n
\u8fbe\u5230\u4e86\u61d2\u52a0\u8f7d\uff0c\u4f46\u662f\u5728\u591a\u7ebf\u7a0b\u4e0d\u80fd\u6b63\u5e38\u5de5\u4f5c\u3002<\/p>\n
public class Singleton {\n    private static Singleton instance;\n    private Singleton () {\n    }\n    public static Singleton getInstance() {\n    if (instance == null) {\n        instance = new Singleton();\n    }\n    return instance;\n    }\n}<\/code><\/pre>\n
\u61d2\u6c49\u6a21\u5f0f\uff08\u7ebf\u7a0b\u5b89\u5168\uff09<\/h3>\n
\u8fd9\u79cd\u5199\u6cd5\u80fd\u591f\u5728\u591a\u7ebf\u7a0b\u4e2d\u5f88\u597d\u7684\u5de5\u4f5c\uff0c\u4f46\u662f\u6bcf\u6b21\u8c03\u7528getInstance\u65b9\u6cd5\u90fd\u4f1a\u8fdb\u884c\u540c\u6b65\uff0c\u53cd\u5e94\u7a0d\u6162\uff0c\u8fd8\u4f1a\u9020\u6210\u4e0d\u5fc5\u8981\u7684\u5f00\u9500\uff0c\u6240\u4ee5\u8005\u8fd9\u79cd\u4e0d\u5efa\u8bae\u4f7f\u7528\u3002<\/p>\n
public class Singleton {\n    private static Singleton instance;\n    private Singleton () {\n    }\n    \/\/\u65b9\u6cd5\u540c\u6b65\u5b9e\u73b0\n    public static synchronized Singleton getInstance() {\n        if (instance == null) {\n            instance = new Singleton();\n        }\n    }\n    \/\/\u4ee3\u7801\u5757\u540c\u6b65\u5b9e\u73b0\n    public static Singleton getInstance() {\n        synchronized(Singleton.class) {\n            if (instance == null) {\n                instance = new Singleton();\n            }\n        }\n    }\n    return instance;\n}<\/code><\/pre>\n
DCL\u5355\u4f8b\uff08\u53cc\u91cd\u68c0\u67e5\u9501\u5b9a\uff09<\/h3>\n
\u8fd9\u79cd\u5199\u6cd5\u5728getSingleton\u65b9\u6cd5\u4e2d\u5bf9singleton\u8fdb\u884c\u4e86\u4e24\u6b21\u5224\u7a7a\uff0c\u7b2c\u4e00\u6b21\u662f\u4e3a\u4e86\u4e0d\u5fc5\u8981\u7684\u540c\u6b65\uff0c\u7b2c\u4e8c\u6b21\u662f\u4e3a\u4e86\u5728null\u7684\u60c5\u51b5\u4e0b\u521b\u5efa\u5b9e\u4f8b\u3002\u6211\u4eec\u4f1a\u53d1\u73b0\u4e0a\u9762\u4ee3\u7801\u6709\u4e00\u4e2avolatile<\/code>\u5173\u952e\u5b57\uff0c\u56e0\u4e3a\u5728\u8fd9\u91cc\u4f1a\u6709DCL\u5931\u6548\u95ee\u9898\uff0c\u539f\u56e0\u662fJava\u7f16\u8bd1\u5668\u5141\u8bb8\u5904\u7406\u5668\u4e71\u5e8f\u6267\u884c\u3002\u90a3\u4e48\u4e3a\u4e86\u89e3\u51b3\u8fd9\u4e2a\u95ee\u9898\uff0c\u5728JDK1.5\u4e4b\u540e\uff0c\u5177\u4f53\u5316\u4e86volatile<\/code>\u5173\u952e\u5b57\uff0c\u53ea\u8981\u5b9a\u4e49\u65f6\u52a0\u4e0a\u4ed6\uff0c\u53ef\u4ee5\u4fdd\u8bc1\u6267\u884c\u7684\u987a\u5e8f\uff0c\u867d\u7136\u4f1a\u5f71\u54cd\u6027\u80fd\u3002\u8fd9\u79cd\u65b9\u5f0f\u7b2c\u4e00\u6b21\u52a0\u8f7d\u65f6\u4f1a\u7a0d\u6162\uff0c\u5728\u9ad8\u5e76\u53d1\u73af\u5883\u4f1a\u6709\u7f3a\u9677\uff0c\u4f46\u662f\u4e00\u822c\u80fd\u591f\u6ee1\u8db3\u9700\u6c42\u3002<\/p>\n
    \n
  • \u4e0d\u8db3\u4e4b\u5904\uff1asingleton = new Singleton()<\/code>\u4e0d\u662f\u539f\u5b50\u64cd\u4f5c\uff0cJVM\u7684\u5373\u65f6\u7f16\u8bd1\u5668\u4e2d\u5b58\u5728\u6307\u4ee4\u91cd\u6392\u5e8f\u7684\u4f18\u5316<\/li>\n
  • volatile\uff1a\u7981\u6b62JVM\u6307\u4ee4\u91cd\u6392\u5e8f\u4f18\u5316<\/li>\n<\/ul>\n
    public class Singleton {\n    private volatile static Singleton singleton;\n    private Singleton () {\n    }\n    public static Singleton getSingleton() {\n        if (singleton == null) {\n            synchronized (Singleton.class) {\n                if (singleton == null) {\n                    singleton = new Singleton();\n                }\n            }\n        }\n        return singleton;\n    }\n}<\/code><\/pre>\n
    \u9759\u6001\u5185\u90e8\u7c7b\u5355\u4f8b\u6a21\u5f0f<\/h3>\n
    \u8fd9\u79cd\u662f\u63a8\u8350\u4f7f\u7528\u7684\u5355\u4f8b\u6a21\u5f0f\u5b9e\u73b0\u65b9\u5f0f\u3002\u5f53\u7b2c\u4e00\u6b21\u52a0\u8f7dSingleton\u7c7b\u65f6\u5e76\u4e0d\u4f1a\u521d\u59cb\u5316INSTANCE\uff0c\u53ea\u6709\u5728\u7b2c\u4e00\u6b21\u8c03\u7528getInstance\u65b9\u6cd5\u65f6\u624d\u4f1a\u5bfc\u81f4INSTANCE\u88ab\u521d\u59cb\u5316\u3002\u8fd9\u79cd\u65b9\u5f0f\u4e0d\u4ec5\u80fd\u591f\u4fdd\u8bc1\u7ebf\u7a0b\u5b89\u5168\uff0c\u4e5f\u80fd\u4fdd\u8bc1\u5355\u4f8b\u5bf9\u8c61\u7684\u552f\u4e00\u6027\uff0c\u540c\u65f6\u4e5f\u5ef6\u957f\u4e86\u5355\u4f8b\u7684\u5b9e\u4f8b\u5316\u3002<\/p>\n
    public class Singleton {\n    private Singleton () {\n    }\n    public static final Singleton getInstance() {\n        return SingletonHolder.INSTANCE;\n    }\n    \/**\n     * \u9759\u6001\u5185\u90e8\u7c7b\n     *\/\n    private static class SingletonHolder {\n        private static final Singleton INSTANCE = new Singleton();\n    }\n}<\/code><\/pre>\n
    \u679a\u4e3e\u5355\u4f8b<\/h3>\n
    \u8fd9\u79cd\u65b9\u5f0f\u662fEffective Java\u4f5c\u8005Josh Bloch \u63d0\u5021\u7684\u65b9\u5f0f\uff0c\u5b83\u4e0d\u4ec5\u80fd\u907f\u514d\u591a\u7ebf\u7a0b\u540c\u6b65\u95ee\u9898\uff0c\u800c\u4e14\u8fd8\u80fd\u9632\u6b62\u53cd\u5e8f\u5217\u5316\u91cd\u65b0\u521b\u5efa\u65b0\u7684\u5bf9\u8c61\u3002<\/p>\n
    public enum Singleton {\n    INSTANCE;\n    public void whateverMethod() {\n    }\n}<\/code><\/pre>\n
    \u4f7f\u7528\u5bb9\u5668\u5b9e\u73b0\u5355\u4f8b\u6a21\u5f0f<\/h3>\n
    \u5c06\u591a\u79cd\u5355\u4f8b\u7c7b\u578b\u6ce8\u5165\u5230\u4e00\u4e2a\u7edf\u4e00\u7684\u7ba1\u7406\u7c7b\u4e2d\uff0c\u5728\u4f7f\u7528\u65f6\u6839\u636ekey\u83b7\u53d6\u5bf9\u8c61\u5bf9\u5e94\u7c7b\u578b\u7684\u5bf9\u8c61\u3002\u8fd9\u79cd\u65b9\u5f0f\u4f7f\u5f97\u6211\u4eec\u53ef\u4ee5\u7ba1\u7406\u591a\u79cd\u7c7b\u578b\u7684\u5355\u4f8b\uff0c\u5e76\u4e14\u5728\u4f7f\u7528\u65f6\u53ef\u4ee5\u901a\u8fc7\u7edf\u4e00\u7684\u63a5\u53e3\u8fdb\u884c\u83b7\u53d6\u64cd\u4f5c\uff0c\u964d\u4f4e\u4e86\u7528\u6237\u7684\u4f7f\u7528\u6210\u672c\uff0c\u4e5f\u5bf9\u7528\u6237\u9690\u85cf\u4e86\u5177\u4f53\u5b9e\u73b0\uff0c\u964d\u4f4e\u4e86\u8026\u5408\u5ea6\u3002<\/p>\n
    public class SingletonManager {\n\u3000\u3000private static Map<String, Object> objMap = new HashMap<String, Object>();\n\n\u3000\u3000private SingletonManager() { }\n\u3000\u3000public static void registerService(String key, Objectinstance) {\n\u3000\u3000\u3000\u3000if (!objMap.containsKey(key) ) {\n\u3000\u3000\u3000\u3000\u3000\u3000objMap.put(key, instance) ;\n\u3000\u3000\u3000\u3000}\n\u3000\u3000}\n\n\u3000\u3000public static ObjectgetService(String key) {\n\u3000\u3000\u3000\u3000return objMap.get(key) ;\n\u3000\u3000}\n}<\/code><\/pre>\n
    Android\u6e90\u7801\u4e2d\u7684\u5355\u4f8b\u6a21\u5f0f<\/h2>\n
    \u5728Android\u7cfb\u7edf\u4e2d\uff0c\u6211\u4eec\u7ecf\u5e38\u4f1a\u901a\u8fc7Context\u83b7\u53d6\u7cfb\u7edf\u7ea7\u522b\u7684\u670d\u52a1\uff0c\u5982WindowsManagerService<\/code>\u3001ActivityManagerService<\/code>\u7b49\uff0c\u66f4\u5e38\u7528\u7684\u662f\u4e00\u4e2aLayoutInflater<\/code>\u7684\u7c7b\uff0c\u8fd9\u4e9b\u670d\u52a1\u4f1a\u5728\u5408\u9002\u7684\u65f6\u5019\u4ee5\u5355\u4f8b\u7684\u5f62\u5f0f\u6ce8\u518c\u5728\u7cfb\u7edf\u4e2d\uff0c\u5728\u6211\u4eec\u9700\u8981\u7684\u65f6\u5019\u5c31\u901a\u8fc7Context<\/code>\u7684getSystemService(String name)<\/code>\u83b7\u53d6\u3002<\/p>\n
    \u603b\u7ed3<\/h2>\n
    \u4f18\u70b9\uff1a<\/p>\n
    \uff081\uff09\u7531\u4e8e\u5355\u4f8b\u6a21\u5f0f\u5728\u5185\u5b58\u4e2d\u53ea\u6709\u4e00\u4e2a\u5b9e\u4f8b\uff0c\u51cf\u5c11\u4e86\u5185\u5b58\u5f00\u652f\uff0c\u7279\u522b\u662f\u4e00\u4e2a\u5bf9\u8c61\u9700\u8981\u9891\u7e41\u7684\u521b\u5efa\u3001\u9500\u6bc1\u65f6\uff0c\u800c\u4e14\u521b\u5efa\u6216\u9500\u6bc1\u65f6\u6027\u80fd\u53c8\u65e0\u6cd5\u4f18\u5316\uff0c\u5355\u4f8b\u6a21\u5f0f\u7684\u4f18\u52bf\u5c31\u975e\u5e38\u660e\u663e\u3002
    \n\uff082\uff09\u5355\u4f8b\u6a21\u5f0f\u53ef\u4ee5\u907f\u514d\u5bf9\u8d44\u6e90\u7684\u591a\u91cd\u5360\u7528\uff0c\u4f8b\u5982\u4e00\u4e2a\u6587\u4ef6\u64cd\u4f5c\uff0c\u7531\u4e8e\u53ea\u6709\u4e00\u4e2a\u5b9e\u4f8b\u5b58\u5728\u5185\u5b58\u4e2d\uff0c\u907f\u514d\u5bf9\u540c\u4e00\u8d44\u6e90\u6587\u4ef6\u7684\u540c\u65f6\u64cd\u4f5c\u3002
    \n\uff083\uff09\u5355\u4f8b\u6a21\u5f0f\u53ef\u4ee5\u5728\u7cfb\u7edf\u8bbe\u7f6e\u5168\u5c40\u7684\u8bbf\u95ee\u70b9\uff0c\u4f18\u5316\u548c\u5171\u4eab\u8d44\u6e90\u8bbf\u95ee\uff0c\u4f8b\u5982\uff0c\u53ef\u4ee5\u8bbe\u8ba1\u4e00\u4e2a\u5355\u4f8b\u7c7b\uff0c\u8d1f\u8d23\u6240\u6709\u6570\u636e\u8868\u7684\u6620\u5c04\u5904\u7406\u3002<\/p>\n
    \u7f3a\u70b9\uff1a<\/p>\n
    \uff081\uff09\u5355\u4f8b\u6a21\u5f0f\u4e00\u822c\u6ca1\u6709\u63a5\u53e3\uff0c\u6269\u5c55\u5f88\u56f0\u96be\uff0c\u82e5\u8981\u6269\u5c55\uff0c\u53ea\u80fd\u4fee\u6539\u4ee3\u7801\u6765\u5b9e\u73b0\u3002
    \n\uff082\uff09\u5355\u4f8b\u5bf9\u8c61\u5982\u679c\u6301\u6709Context\uff0c\u90a3\u4e48\u5f88\u5bb9\u6613\u5f15\u53d1\u5185\u5b58\u6cc4\u9732\u3002\u6b64\u65f6\u9700\u8981\u6ce8\u610f\u4f20\u9012\u7ed9\u5355\u4f8b\u5bf9\u8c61\u7684Context<\/code>\u6700\u597d\u662fApplication Context<\/code>\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"
    \u5355\u4f8b\u6a21\u5f0f\u7684\u4f5c\u7528\u662f\u786e\u4fdd\u67d0\u4e2a\u7c7b\u53ea\u6709\u4e00\u4e2a\u5b9e\u4f8b\uff0c\u907f\u514d\u4ea7\u751f\u591a\u4e2a\u5bf9\u8c61\u6d88\u8017\u8fc7\u591a\u7684\u8d44\u6e90\u3002\u6bd4\u5982\u5bf9\u6570\u636e\u5e93\u7684\u64cd\u4f5c\u65f6\uff0c\u5c31\u53ef\u4ee5\u4f7f\u7528\u5355\u4f8b\u6a21 […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[303],"tags":[],"class_list":["post-1111","post","type-post","status-publish","format-standard","hentry","category-design-pattern"],"_links":{"self":[{"href":"https:\/\/www.appblog.cn\/index.php\/wp-json\/wp\/v2\/posts\/1111","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.appblog.cn\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.appblog.cn\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.appblog.cn\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.appblog.cn\/index.php\/wp-json\/wp\/v2\/comments?post=1111"}],"version-history":[{"count":0,"href":"https:\/\/www.appblog.cn\/index.php\/wp-json\/wp\/v2\/posts\/1111\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.appblog.cn\/index.php\/wp-json\/wp\/v2\/media?parent=1111"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.appblog.cn\/index.php\/wp-json\/wp\/v2\/categories?post=1111"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.appblog.cn\/index.php\/wp-json\/wp\/v2\/tags?post=1111"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}