{"id":10006840,"date":"2022-11-09T10:32:06","date_gmt":"2022-11-09T02:32:06","guid":{"rendered":"https:\/\/ityet.com\/?p=10006840"},"modified":"2022-11-09T10:32:06","modified_gmt":"2022-11-09T02:32:06","slug":"%e9%9d%a2%e8%af%95%e5%ae%98%ef%bc%9a%e5%9c%a8-java-%e4%b8%ad-new-%e4%b8%80%e4%b8%aa%e5%af%b9%e8%b1%a1%e7%9a%84%e6%b5%81%e7%a8%8b%e6%98%af%e6%80%8e%e6%a0%b7%e7%9a%84%ef%bc%9f%e5%bd%bb%e5%ba%95%e8%a2%ab","status":"publish","type":"post","link":"https:\/\/itmax.cn\/?p=10006840","title":{"rendered":"\u9762\u8bd5\u5b98\uff1a\u5728 Java \u4e2d new \u4e00\u4e2a\u5bf9\u8c61\u7684\u6d41\u7a0b\u662f\u600e\u6837\u7684\uff1f\u5f7b\u5e95\u88ab\u95ee\u61f5\u4e86\u3002\u3002"},"content":{"rendered":"

\u5bf9\u8c61\u600e\u4e48\u521b\u5efa\uff0c\u8fd9\u4e2a\u592a\u719f\u6089\u4e86\uff0cnew\u4e00\u4e0b(\u5176\u5b9e\u8fd8\u6709\u5f88\u591a\u9014\u5f84\uff0c\u6bd4\u5982\u53cd\u5c04\u3001\u53cd\u5e8f\u5217\u5316\u3001clone\u7b49\uff0c\u8fd9\u91cc\u62ff\u6700\u7b80\u5355\u7684new\u6765\u8bb2)\uff1a<\/p>\n

Dog dog = new Dog();<\/code><\/pre>\n
\u6211\u4eec\u603b\u662f\u4e60\u60ef\u4e8e\u56fa\u5b9a\u8bed\u53e5\u7684\u6267\u884c\uff0c\u5374\u5bf9\u4e8e\u80cc\u540e\u7684\u5b9e\u73b0\u8fc7\u7a0b\u7f3a\u4e4f\u8ba4\u77e5\uff0c\u800c\u7406\u89e3\u8fd9\u4e2a\u8fc7\u7a0b\u5bf9\u540e\u9762\u6666\u6da9\u96be\u61c2\u7684\u53cd\u5c04\u548c\u4ee3\u7406\u5176\u5b9e\u4f1a\u6709\u5f88\u5927\u5e2e\u52a9\uff0c\u6240\u4ee5\u8bf7\u52a1\u5fc5\u5b66\u597d\u8fd9\u5757\u5185\u5bb9\u3002<\/p>\n
\u5728\u770b\u8fd9\u7bc7\u6587\u7ae0\u4e4b\u524d\uff0c\u5570\u55e6\u4e00\u53e5\uff1a\u5982\u679c\u4f60\u6b7b\u8bb0\u786c\u80cc\u4e0b\u9762\u6240\u8bf4\u7684\u6d41\u7a0b\u7b49\u4e8e\u767d\u770b\uff0c\u5c31\u7b97\u73b0\u5728\u8bb0\u4f4f\u4e86\uff0c\u4e00\u4e2a\u793c\u62dc\u540e\u5462\uff0c\u4e00\u4e2a\u6708\u540e\u4f60\u53c8\u80fd\u8bb0\u5f97\u591a\u5c11\uff0c\u56e0\u4e3a\u5bf9\u8c61\u521b\u5efa\u8fc7\u7a0b\u8fd9\u4e2a\u77e5\u8bc6\u70b9\u5e73\u5e38\u7684\u5de5\u4f5c\u4e2d\u57fa\u672c\u4e0d\u4f1a\u6d89\u53ca\u5230\uff0c\u592a\u5e95\u5c42\u4e86\uff0c\u80cc\u719f\u7684\u77e5\u8bc6\u70b9\u4e0d\u7ecf\u5e38\u52a0\u4ee5\u8fd0\u7528\u5bb9\u6613\u9057\u5fd8\uff0c\u6240\u4ee5\u6211\u7684\u5efa\u8bae\u662f\u4ec0\u4e48\u5462\uff0c\u6d41\u7a0b\u505a\u5230\u5fc3\u91cc\u5927\u6982\u6709\u4e2a\u6570\uff0c\u5176\u4e2d\u6d89\u53ca\u5230\u5173\u952e\u7684\u77e5\u8bc6\u70b9\u8bb0\u7262\u5c31\u53ef\u4ee5\u4e86\u3002<\/p>\n
JVM\u5185\u5b58<\/h3>\n
\u5148\u7b80\u5355\u8bf4\u4e0bjava\u865a\u62df\u673a\u5185\u5b58\u6a21\u578b\u548c\u5b58\u653e\u5185\u5bb9\u7684\u533a\u522b\uff0c\u4e24\u90e8\u5206\uff1a<\/p>\n
    \n
  • \u6808\u5185\u5b58 \u5b58\u653e\u57fa\u672c\u7c7b\u578b\u6570\u636e\u548c\u5bf9\u8c61\u7684\u5f15\u7528\u53d8\u91cf\uff0c\u6570\u636e\u53ef\u4ee5\u76f4\u63a5\u62ff\u6765\u8bbf\u95ee\uff0c\u901f\u5ea6\u6bd4\u5806\u5feb<\/li>\n
  • \u5806\u5185\u5b58 \u5b58\u653e\u521b\u5efa\u7684\u5bf9\u8c61\u548c\u6570\u7ec4\uff0c\u4f1a\u7531java\u865a\u62df\u673a\u7684\u81ea\u52a8\u5783\u573e\u56de\u6536\u6765\u7ba1\u7406\uff08GC\uff09,\u521b\u5efa\u4e00\u4e2a\u5bf9\u8c61\u653e\u5165\u5806\u5185\u7684\u540c\u65f6\u4e5f\u4f1a\u5728\u6808\u4e2d\u521b\u5efa\u4e00\u4e2a\u6307\u5411\u8be5\u5bf9\u8c61\u5806\u5185\u5b58\u4e2d\u7684\u5730\u5740\u5f15\u7528\u53d8\u91cf\uff0c\u4e0b\u9762\u8bf4\u7684\u5bf9\u8c61\u5c31\u662f\u5b58\u5728\u8be5\u5185\u5b58\u4e2d<\/li>\n<\/ul>\n
    \u4e0b\u9762\u6211\u4eec\u5c31\u6309\u7167\u5bf9\u8c61\u751f\u6210\u7684\u8fc7\u7a0b\u6765\u4e00\u4e00\u8bb2\u89e3\u53c2\u4e0e\u5176\u4e2d\u8fc7\u7a0b\u7684\u5404\u4e2a\u6982\u5ff5<\/p>\n
    \u9996\u5148\u6709\u8fd9\u4e48\u4e00\u4e2a\u7c7b\uff0c\u540e\u9762\u7684\u521d\u59cb\u5316\u57fa\u4e8e\u8fd9\u4e2a\u8bb2\u89e3\uff1a<\/p>\n
    \/**\n * @author \u709c\u54e5\n * @since 2021-04-18 11:01:41\n *\n * \u6267\u884c\u987a\u5e8f\uff1a\uff08\u4f18\u5148\u7ea7\u4ece\u9ad8\u5230\u4f4e\u3002\uff09\u9759\u6001\u4ee3\u7801\u5757>\u6784\u9020\u4ee3\u7801\u5757>\u6784\u9020\u65b9\u6cd5>\u666e\u901a\u65b9\u6cd5\u3002\n * \u5176\u4e2d\u9759\u6001\u4ee3\u7801\u5757\u53ea\u6267\u884c\u4e00\u6b21\u3002\u6784\u9020\u4ee3\u7801\u5757\u5728\u6bcf\u6b21\u521b\u5efa\u5bf9\u8c61\u662f\u90fd\u4f1a\u6267\u884c\u3002\n *\/\npublic class Dog {\n\n    \/\/\u9ed8\u8ba4\u72d7\u72d7\u7684\u6700\u5927\u5e74\u9f84\u662f16\u5c81\n    private static int dog_max_age = 16;\n\n    \/\/\u72d7\u72d7\u7684\u540d\u5b57\n    private String dog_name;\n\n    {\n        System.out.println("\u72d7\u72d7\u7684\u6784\u9020\u4ee3\u7801\u5757");\n    }\n\n    static {\n        System.out.println("\u72d7\u72d7\u7684\u9759\u6001\u4ee3\u7801\u5757");\n    }\n\n    \/\/\u65e0\u53c2\u6784\u9020\u5668\u6545\u610f\u6ca1\u8bbe\n    \/\/\u6709\u53c2\u6784\u9020\u5668\n    public Dog(String dog_name) {\n        this.dog_name = dog_name;\n    }\n\n    public void getDogInfo(){\n        System.out.println("\u540d\u5b57\u662f:"+dog_name + "  \u5e74\u9f84\uff1a" + dog_max_age);\n    }\n\n    \/\/\u72d7\u53eb\n    public static void barking(){\n        System.out.println("\u6c6a\u6c6a\u6c6a~~~");\n    }\n}<\/code><\/pre>\n
    JVM\u751f\u6210.class\u6587\u4ef6<\/h3>\n
    \u4e00\u4e2ajava\u6587\u4ef6\u4f1a\u5728\u7f16\u8bd1\u671f\u95f4\u88ab\u521d\u59cb\u5316\u751f\u6210.class\u5b57\u8282\u7801\u6587\u4ef6\uff0c\u5b57\u8282\u7801\u6587\u4ef6\u662f\u4e13\u95e8\u7ed9JVM\u9605\u8bfb\u7684\uff0c\u6211\u4eec\u5e73\u65f6\u542d\u54e7\u542d\u54e7\u5199\u7684\u4e00\u884c\u884c\u4ee3\u7801\u6700\u7ec8\u90fd\u4f1a\u88ab\u7f16\u8bd1\u6210\u673a\u5668\u80fd\u770b\u61c2\u7684\u8bed\u53e5\uff0c\u8fd9\u4e2a\u6587\u4ef6\u540e\u9762\u4f1a\u88ab\u7c7b\u52a0\u8f7d\u5668\u52a0\u8f7d\u5230\u5185\u5b58\u3002<\/p>\n
    \"\"<\/p>\n
    \u7c7b\u52a0\u8f7d\u5668\u52a0\u8f7d.class\u6587\u4ef6<\/h3>\n
    \u300a\u6df1\u5165\u7406\u89e3Java\u7684\u865a\u62df\u673a\u300b\u4e2d\u5927\u6982\u6709\u8fd9\u4e48\u4e00\u53e5\u8bdd\uff1a\u5728\u865a\u62df\u673a\u9047\u5230\u4e00\u6761new\u7684\u6307\u4ee4\u65f6\uff0c\u4f1a\u53bb\u68c0\u67e5\u4e00\u904d\u5728\u9759\u6001\u5e38\u91cf\u6c60\u4e2d\u80fd\u5426\u5b9a\u4f4d\u5230\u4e00\u4e2a\u7c7b\u7684\u7b26\u53f7\u5f15\u7528 \uff08\u5c31\u8fd9\u4e2a\u7c7b\u7684\u8def\u5f84+\u540d\u5b57\uff09\uff0c\u5e76\u4e14\u68c0\u67e5\u8fd9\u4e2a\u7b26\u53f7\u5f15\u7528\u4ee3\u8868\u7684\u7c7b\u662f\u5426\u5df2\u88ab\u52a0\u8f7d\u3001\u89e3\u6790\u548c\u521d\u59cb\u5316\u8fc7\u3002\u5982\u679c\u4e0d\u662f\u7b2c\u4e00\u6b21\u4f7f\u7528\uff0c\u90a3\u5fc5\u987b\u5148\u6267\u884c\u76f8\u5e94\u7684\u7c7b\u52a0\u8f7d\u8fc7\u7a0b\uff0c\u8fd9\u4e2a\u8fc7\u7a0b\u7531\u7c7b\u52a0\u8f7d\u5668\u6765\u5b8c\u6210\u3002<\/p>\n
    \u7c7b\u52a0\u8f7d\u5b57\u9762\u610f\u601d\u5c31\u53ef\u4ee5\u7406\u89e3\u6210\u52a0\u8f7dclass\u6587\u4ef6\uff0c\u66f4\u51c6\u786e\u70b9\u7684\u8bf4\u6cd5\u5c31\u662f\u4f1a\u628aclass\u6587\u4ef6\u53d8\u6210\u4e00\u4e2a\u4e8c\u8fdb\u5236\u6d41\u52a0\u8f7d\u5230\u5185\u5b58\u4e2d\uff0c\u5373\u628a\u7c7b\u7684\u63cf\u8ff0\u4fe1\u606f\u52a0\u8f7d\u5230Metaspace\uff0c\u81f3\u4e8e\u7c7b\u52a0\u8f7d\u5668\u5982\u4f55\u627e\u5230\u5e76\u628a\u4e00\u4e2aclass\u6587\u4ef6\u8f6c\u6210IO\u6d41\u52a0\u8f7d\u5230\u5185\u5b58\u4e2d\uff0c\u6211\u540e\u9762\u4f1a\u4e13\u95e8\u5199\u4e00\u7bc7\u5173\u4e8e\u7c7b\u52a0\u8f7d\u5668\u7684\u6587\u7ae0\uff0c\u8fd9\u91cc\u5c31\u53ea\u8981\u7406\u89e3\u521b\u5efa\u5bf9\u8c61\u4e2d\u6709\u8fd9\u4e48\u4e00\u6b65\u5c31\u884c\u4e86\u3002\u4e0d\u8fc7\u8fd9\u91cc\u9762\u6709\u5f88\u91cd\u8981\u7684\u6982\u5ff5\u4e0d\u5f97\u4e0d\u8bb2\uff1aClass\u5bf9\u8c61<\/p>\n
    \u77e5\u8bc6\u6269\u5c55\uff1aClass\u5bf9\u8c61<\/h4>\n
    \u5212\u91cd\u70b9\uff0c\u8fd9\u662f\u4e2a\u975e\u5e38\u91cd\u8981\u7684\u6982\u5ff5\uff0c\u7406\u89e3\u5b83\u5bf9\u4e8e\u7406\u89e3\u540e\u9762\u7684\u53cd\u5c04\u548c\u4ee3\u7406\u4f1a\u6709\u5f88\u5927\u7684\u5e2e\u52a9<\/p>\n
    \u7c7b\u52a0\u8f7d\u5668 ClassLoader \u52a0\u8f7dclass\u6587\u4ef6\u65f6\uff0c\u4f1a\u628a\u7c7b\u91cc\u7684\u4e00\u4e9b\u6570\u503c\u5e38\u91cf\u3001\u65b9\u6cd5\u3001\u7c7b\u4fe1\u606f\u7b49\u52a0\u8f7d\u5230\u5185\u5b58\u4e2d\uff0c\u79f0\u4e4b\u4e3a\u7c7b\u7684\u5143\u6570\u636e\uff0c\u6700\u7ec8\u76ee\u7684\u662f\u4e3a\u4e86\u751f\u6210\u4e00\u4e2aClass\u5bf9\u8c61\u7528\u6765\u63cf\u8ff0\u7c7b\uff0c\u8fd9\u4e2a\u5bf9\u8c61\u4f1a\u88ab\u4fdd\u5b58\u5728.class\u6587\u4ef6\u91cc\uff0c\u53ef\u80fd\u6709\u65b0\u624b\u770b\u5230\u8fd9\u91cc\u4f1a\u6bd4\u8f83\u61f5\u903c\uff0cclass\u4e5f\u6709\u5bf9\u8c61\uff1f<\/p>\n
    \u5f53\u7136\u4e86\uff0cClass\u662f\u4e2a\u5b9e\u5b9e\u5728\u5728\u7684\u7c7b\uff08\u7528\u6765\u63cf\u8ff0\u7c7b\u7684\u7c7b\uff0c\u6bd4\u8f83\u62d7\u53e3\uff09\uff0c\u6709\u6784\u9020\u65b9\u6cd5\uff08 private \uff0c\u610f\u5473\u7740\u53ef\u4ee5\u751f\u6210\u5bf9\u8c61\uff0c\u4f46\u4e0d\u80fd\u624b\u52a8\u751f\u6210\uff0c\u7531JVM\u81ea\u52a8\u521b\u5efaClass\u5bf9\u8c61\uff09,\u7c7b\u52a0\u8f7d\u5668\u4f1a\u7ed9\u6bcf\u4e2ajava\u6587\u4ef6\u90fd\u521b\u5efa\u4e00\u4e2aClass\u5bf9\u8c61\uff0c\u7528\u6765\u63cf\u8ff0\u7c7b\uff0c\u6211\u753b\u4e2a\u56fe\uff1a<\/p>\n
    \"\"<\/p>\n
    \/\/\u4ee5\u4e0b\u64cd\u4f5c\u53ea\u80fd\u7531jvm\u5b8c\u6210\uff0c\u6211\u4eec\u624b\u52a8\u505a\u4e0d\u4e86\nClass cls1 = new Class(Dog.class.getClassLoader());\nClass cls2 = new Class(Cat.class.getClassLoader());\nClass cls3 = new Class(People.class.getClassLoader());<\/code><\/pre>\n
    \"\"<\/p>\n
    \u8fd9\u4e2aClass\u5bf9\u8c61\u9664\u4e86\u63cf\u8ff0\u5bf9\u5e94\u7684\u7c7b\u4e4b\u5916\u8fd8\u6709\u4ec0\u4e48\u4f5c\u7528\u5462\uff1f\u4e5f\u53ef\u4ee5\u751f\u6210\u5bf9\u8c61\uff0c\u5c31\u662fjava\u7684\u53cd\u5c04\u6982\u5ff5\uff08\u901a\u8fc7Class\u5b9e\u4f8b\u83b7\u53d6\u7c7b\u4fe1\u606f\uff09 \u4e0a\u9762\u8bf4\u4e86\uff0cClass\u7c7b\u662f\u7528\u6765\u63cf\u8ff0\u50cfPeople.Class\u7c7b\u7684\u7c7b\uff0c\u90a3\u4e48\u5b83\u91cc\u9762\u80af\u5b9a\u5305\u542b\u4e86\u6240\u6709\u80fd\u591f\u63cf\u8ff0\u8be5class\u7684\u6240\u6709\u5c5e\u6027\uff0c\u6bd4\u5982\u7c7b\u540d\u3001\u65b9\u6cd5\u3001\u63a5\u53e3\u7b49\uff0c\u6211\u4eec\u5148\u5230Class\u7c7b\u6e90\u7801\u4e2d\u7784\u4e00\u773c\uff1a<\/p>\n
    \"\"<\/p>\n
    \u8fd9\u91cc\u9762\u6709\u4e2a\u65b9\u6cd5 newInstance()<\/code>\uff0c\u5373\u521b\u5efa\u5bf9\u8c61\uff0c \u6211\u628a\u6e90\u4ee3\u7801\u8d34\u51fa\u6765\u5e76\u7b80\u5355\u89e3\u6790\u4e0b\uff1a<\/p>\n
    @CallerSensitive\npublic T newInstance()\n    throws InstantiationException, IllegalAccessException\n    {\n\n        if (System.getSecurityManager() != null) {\n            checkMemberAccess(Member.PUBLIC, Reflection.getCallerClass(), false);\n        }\n\n        if (cachedConstructor == null) {\n            if (this == Class.class) {\n                throw new IllegalAccessException(\n                    "Can not call newInstance() on the Class for java.lang.Class"\n                );\n            }\n            try {\n                Class<?>[] empty = {};\n                \/\/\u58f0\u660e\u65e0\u53c2\u6784\u9020\u5bf9\u8c61\n                final Constructor<T> c = getConstructor0(empty, Member.DECLARED);\n                \/\/ Disable accessibility checks on the constructor\n                \/\/ since we have to do the security check here anyway\n                \/\/ (the stack depth is wrong for the Constructor's\n                \/\/ security check to work)\n                java.security.AccessController.doPrivileged(\n                    new java.security.PrivilegedAction<Void>() {\n                        public Void run() {\n                                c.setAccessible(true);\n                                return null;\n                            }\n                        });\n                cachedConstructor = c;\n            } catch (NoSuchMethodException e) {\n             \/\/\u5982\u679cclass\u4e2d\u6ca1\u6709\u65e0\u53c2\u6784\u9020\u65b9\u6cd5\uff0c\u90a3\u4e48\u629bInstantiationException\u9519\u8bef\n                throw (InstantiationException)\n                    new InstantiationException(getName()).initCause(e);\n            }\n        }\n        Constructor<T> tmpConstructor = cachedConstructor;\n        \/\/ Security check (same as in java.lang.reflect.Constructor)\n        int modifiers = tmpConstructor.getModifiers();\n        if (!Reflection.quickCheckMemberAccess(this, modifiers)) {\n            Class<?> caller = Reflection.getCallerClass();\n            if (newInstanceCallerCache != caller) {\n                Reflection.ensureMemberAccess(caller, this, null, modifiers);\n                newInstanceCallerCache = caller;\n            }\n        }\n        \/\/ Run constructor\n        try {\n         \/\/\u6700\u7ec8\u8fd8\u662f\u8c03\u7528\u4e86\u65e0\u53c2\u6784\u9020\u5668\u5bf9\u8c61\u7684newInstance\u65b9\u6cd5\n            return tmpConstructor.newInstance((Object[])null);\n        } catch (InvocationTargetException e) {\n            Unsafe.getUnsafe().throwException(e.getTargetException());\n            \/\/ Not reached\n            return null;\n        }\n    }<\/code><\/pre>\n
    \u9996\u5148\u641e\u6e05\u695a newInstance \u4e24\u79cd\u65b9\u6cd5\u533a\u522b\uff1a<\/strong><\/p>\n
    Class.newInstance() <\/code>\u53ea\u80fd\u591f\u8c03\u7528\u65e0\u53c2\u7684\u6784\u9020\u51fd\u6570\uff0c\u5373\u9ed8\u8ba4\u7684\u6784\u9020\u51fd\u6570\uff0c\u6211\u4eec\u5728Class\u6e90\u7801\u91cc\u4e5f\u770b\u5230\u4e86\u5176\u5b9e\u6700\u7ec8\u8fd8\u662f\u8c03\u7528\u4e86\u65e0\u53c2\u6784\u9020\u5668\u5bf9\u8c61 Constructor<\/code> \u7684 newInstance<\/code> \u65b9\u6cd5\uff0c\u4e3e\u4e2a\u6817\u5b50\uff1aDog.class \u4e2d\u662f\u6ca1\u6709\u65e0\u53c2\u6784\u9020\u65b9\u6cd5\uff0c\u90a3\u4e48\u4f1a\u76f4\u63a5\u629b\u51fa InstantiationException<\/code> \u5f02\u5e38\uff1a<\/p>\n
    \/\/Dog\u7c7b\u4e2d\u53ea\u6709\u4e00\u4e2adog_name\u7684\u6709\u53c2\u6784\u9020\u65b9\u6cd5\nClass c = Class.forName("com.service.ClassAnalysis.Dog");\nDog dog = (Dog) c.newInstance();\/\/\u76f4\u63a5\u629bInstantiationException\u5f02\u5e38<\/code><\/pre>\n
    \"\"<\/p>\n
    Constructor.newInstance() <\/code>\u53ef\u4ee5\u6839\u636e\u4f20\u5165\u7684\u53c2\u6570\uff0c\u8c03\u7528\u4efb\u610f\u6784\u9020\u6784\u9020\u51fd\u6570\uff0c\u4e5f\u53ef\u4ee5\u53cd\u5c04\u79c1\u6709\u6784\u9020\u5668\uff08\u4e86\u89e3\u5c31\u884c\uff09<\/p>\n
    \/\/Dog\u7c7b\u4e2d\u53ea\u6709\u4e00\u4e2adog_name\u7684\u6709\u53c2\u6784\u9020\u65b9\u6cd5\nConstructor cs = Dog.class.getConstructor(String.class);\nDog dog = (Dog) cs.newInstance("\u5c0f\u9ed1");\/\/\u6267\u884c\u6ca1\u6709\u95ee\u9898<\/code><\/pre>\n
    \u4f46\u662f\u8fd9\u91cc\u9762\u7684 newInstance<\/code>\u8ddf\u6211\u4eec\u8fd9\u6b21\u8981\u8bf4\u7684 new \u65b9\u6cd5\u5b58\u5728\u533a\u522b\uff0c\u4e24\u8005\u521b\u5efa\u5bf9\u8c61\u7684\u65b9\u5f0f\u4e0d\u540c\uff0c\u521b\u5efa\u6761\u4ef6\u4e5f\u4e0d\u540c\uff1a<\/p>\n