单例模式

packagecom.awu.springboot.code1.designmode.singlemode;publicclassHungrySingleMode{privatestaticHungrySingleModehungrySingleMode=newHungrySingleMode();privateHungrySingleMode(){}publicstaticHungrySingleModegetSingleInstance(){returnhungrySingleMode;}}packagecom.awu.springboot.code1.designmode.singlemode;publicclassLazySingleMode{privatestaticLazySingleModelazySingleMode=null;privateLazySingleMode(){}publicstaticLazySingleModegetSingleInstance(){if(lazySingleMode==null){lazySingleMode=newLazySingleMode();}returnlazySingleMode;}}packagecom.awu.springboot.code1.designmode.singlemode;publicclassThreadSafeLazySingleMode{privatestaticThreadSafeLazySingleModelazySingleMode=null;privateThreadSafeLazySingleMode(){}publicstaticThreadSafeLazySingleModegetSingleInstance(){if(lazySingleMode==null){synchronized(ThreadSafeLazySingleMode.class){if(lazySingleMode==null){lazySingleMode=newThreadSafeLazySingleMode();}}}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