对于String对象来说,null值是不会被isEmpty校验的,因为null并不是一个空字符串。但是对于集合类对象如List、Map等,null值会被isEmpty校验。具体来说,对于List对象,如果List为null或者List的size为0,则会被认为是空的。 下面通过代码示例来验证上述结论: publicclassMain{publicstaticvoidmain(String[]args){// 测...
No, the isEmpty() method of the java.util.List interface does not check if the list itself is null. It only checks if the list is empty, i.e. if it contains no elements. Here is an example of how the isEmpty() method can be used: import java.util.ArrayList; import java...
null 一个对象如果有可能是null的话,首先要做的就是判断是否为null:object == null,否则就有可能会出现空指针异常,这个通常是我们在进行数据库的查询操作时,查询结果首先用object != null,进行非空判断,然后再进行其他的业务逻辑,这样可以避免出现空指针异常。 isEmpty()此方法可以使用于字符串,数组,集合都可以用...
*@paramobj要判断的对象 *@return对象是否为null,是返回true,否则返回false */publicstaticbooleanisEmpty(Objectobj){if(obj==null){// 判断对象是否为nullreturntrue;// 如果对象为null,返回true}returnfalse;// 如果对象不为null,返回false}publicstaticvoidmain(String[]args){Objectobj=null;// 创建一个null...
_sheepy_ 淼淼淼沝 11 String name=request.getParameter("name");if ( name == null || name.isEmpty() ) name = "default"; 3楼2015-01-02 16:49 收起回复 蜻蜓队长不会打分 司马水 13 打个断点,,还有,控制台难道不报哪一行为空?一清二楚,, 4楼2015-01-02 17:25 回复 ...
public class TestNull { public static void main(String[] args) { String a = new String(); String b = ""; String c = null; if (a.isEmpty()) { System.out.println("String a = new String"); } if (b.isEmpty()) { System.out.println("String b = \"\""); } if (c == ...
Java String类的isEmpty(),null的区别 一、理解 isEmpty()完全等同于string.length()==0 若String对象本身是NULL,即字符串对象的引用是空指针,那在使用String.isEmpty()方法时会提示NullPointerException。 二、
publicclassArrayIsEmptyExample{ publicstaticvoidmain(String[]args){ String[]array1=null; String[]array2=newString[0]; String[]array3={"element"}; System.out.println("array1 是否为空: "+(array1==null||array1.length==0)); System.out.println("array2 是否为空: "+(array2==null||array...
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Here, we can useJava Assertionsinstead of the traditionalnullcheck conditional statement: In line 2, we check for anullparameter.If the assertions are enabled, this would result in anAssertionError. Although it is a good way of asserting preconditions such as non-nullparameters,this approach has...