Java中null、isEmpty的区别？

最新推荐文章于 2024-12-26 13:35:35 发布

Const Empty

最新推荐文章于 2024-12-26 13:35:35 发布

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分类专栏： Java 文章标签： java非空判断

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/** * 区别 * null * isEmpty() 1.""空字符串或对象初始化调用后都返回true 2.null调用报空指针 * " "（空字符串） * @author admin * */public class Test {@SuppressWarnings({ "null", "unused" })public static void main(String[] args) {//分配内存空间，值为空。String a = new String();//分配内存空间，值为空字符串。String b = "";//未分配内存空间,无值String c = null;//isEmpty()if (a.isEmpty()) {System.out.println("a.isEmpty()==true");}if (b.isEmpty()) {System.out.println("b.isEmpty()==true");}/*if (c.isEmpty()) {//未分配空间的c值null，调用isEmpty(),报NullPointExceptionSystem.out.println("c.isEmpty()==true");}*///""if (a=="") {System.out.println("a==\"\"");}if (b=="") {System.out.println("b==\"\"");}if (c=="") {System.out.println("c==\"\"");}//nullif(a ==null){System.out.println("a==null");}if (b==null) {System.out.println("b==null");}if (c==null) {System.out.println("c==null");}}}