publicclassNullCheckExample{publicstaticvoidmain(String[]args){Stringstr=null;// 判断 str 是否为 nullif(str==null){System.out.println("字符串是 null");}else{System.out.println("字符串的长度是: "+str.length());}// 给 str 赋值str="Hello, Java!";// 再次判断 str 是否为 nullif(str==n...
println("The string is null."); } else { System.out.println("The string is not null."); } Employing the Objects.isNull() method: In Java 8 and later versions, you can use the Objects.isNull() method from the java.util.Objects class to check if a string is null. This method ...
if (str3 == null || str3.length() == 0) { System.out.println("str3 is null or empty."); } else { System.out.println("str3 is not null or empty."); } } } The code example demonstrates the if-else method for checking if a string is null or empty in Java. It utilizes ...
在Java中,可以使用if语句来判断一个对象是否为null。如果一个对象的引用为null,那么表示这个对象并未被实例化,或者被赋值为null。在if语句中,可以通过判断对象是否为null来执行相应的逻辑。 Stringstr=null;if(str==null){System.out.println("str对象为null");}else{System.out.println("str对象不为null");} ...
java if判断字符串非空 1publicstaticvoidmain(String[] args) {2String s =null;3String c = " ";4String a =newString("");5String b =newString("");6System.out.println("s:" +s);7System.out.println("a:" +a);8System.out.println("b:" +b);9//根据内存地址判断 false10if(a ==...
Java String trim()Example 1: Check if String is Empty or Null class Main { public static void main(String[] args) { // create null, empty, and regular strings String str1 = null; String str2 = ""; String str3 = " "; // check if str1 is null or empty System.out.println("...
如上两图所示, 我从前台传入一个decidedistribute, 从输出可以看出decidedistribute是有值传入的,而且在if语句判定的时候值还是正确的,但是不知道为什么进了if作用域后就变为空指针了, 输出了null,后面调用也报了空指针异常。 求解,谢谢了javaspring-mvcstring ...
return value == null ? empty() : of(value); } } 再做一个简单的实例展示 与上面对应 // 1、创建一个包装对象值为空的Optional对象 Optional<String> optEmpty = Optional.empty(); // 2、创建包装对象值非空的Optional对象 Optional<String> optOf = Optional.of("optional"); ...
*@paramstring the string that needs to be added to the array. */ publicvoidadd(String string){ elements.add(string ==null? JsonNull.INSTANCE :newJsonPrimitive(string)); } /** * Adds the specified element to self. * *@paramelement the element that needs to be added to the array. ...
It has been part of the String class since Java 11 . Alternatively, we can trim the String and call isEmpty or nonEmpty according to our needs. However, we should remember that all these methods throw a NullPointerException if the reference we use to call is null. 3. Dealing With null...