02 2017 档案
摘要://懒汉模式public class Singleton { private static Singleton instance; /** * 私有化构造方法 */ private Singleton(){ } public static Singleton getInstance(){ if (instance...
阅读全文
摘要:Map map = new HashMap(); String[] string = {"abc","123","234","345","234","234","234","345","345","345","345","234","234"}; for(String s:string){ Integer count = m...
阅读全文
摘要:import java.util.HashMap; import java.util.Iterator; import java.util.Map; public class TestMap { public static void main(String[] args) { Map map = new HashMap(); map.put(1, "a"...
阅读全文
摘要:在foreach循环里做元素的remove/add操作时,例如 会抛出异常java.util.ConcurrentModificationException (以ArrayList来讲解)在ArrayList中,它的修改操作(add/remove)都会对modCount这个字段+1,modCount
阅读全文
摘要:上面的代码输出结果为 0.0600000000000000050.5800000000000001401.499999999999941.2329999999999999 原因在于我们的计算机是二进制的。浮点数没有办法是用二进制进行精确表示。我们的CPU表示浮点数由两个部分组成:指数和尾数,这样的表
阅读全文