灰太狼的博客

String类型 →  int类型 第一种:    String str = "123";                                                     //使用静态方法只产生一个对象                       try{                               int a = Integer.parseI

单线程中的单例模式: public class Sinleton{                    private volatile static Singleton instance;                                private Singleton()   {}                         public static S