单例模式packagecom.awu.springboot.code1.designmode.singlemode;publicclassHungrySingleMode{privatestaticHungrySingleModehungrySingleModenewHungrySingleMode();privateHungrySingleMode(){}publicstaticHungrySingleModegetSingleInstance(){returnhungrySingleMode;}}packagecom.awu.springboot.code1.designmode.singlemode;publicclassLazySingleMode{privatestaticLazySingleModelazySingleModenull;privateLazySingleMode(){}publicstaticLazySingleModegetSingleInstance(){if(lazySingleModenull){lazySingleModenewLazySingleMode();}returnlazySingleMode;}}packagecom.awu.springboot.code1.designmode.singlemode;publicclassThreadSafeLazySingleMode{privatestaticThreadSafeLazySingleModelazySingleModenull;privateThreadSafeLazySingleMode(){}publicstaticThreadSafeLazySingleModegetSingleInstance(){if(lazySingleModenull){synchronized(ThreadSafeLazySingleMode.class){if(lazySingleModenull){lazySingleModenewThreadSafeLazySingleMode();}}}returnlazySingleMode;}}在这之后过了大约30万年物质和能量开始形成复杂的结构称为原子再进一步构成分子。至于这些原子和分子的故事以及它们如何互动就成了化学。人类简史