//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"); //3、创建包装对象值允许为空也可以不为空的Optional对象 Optional<String>optOfNullable1=Optional.ofNullable(null); Optional<Strin...
return Optional.ofNullable(person).orElse("person为null"); ``` 测试展示类Person代码(如果有朋友不明白可以看一下这个): ```java public class Person { private String name; private Integer age; public Person(String name, Integer age) { this.name = name; this.age = age; } public Person() ...
println'str is null'} 这个语句段的执行结果为：str is null 可以看出，if(str)判断语句，当str为null的时候，不执行。可能要问，当str = ''的时候会怎样？def str = ''if(str){ println"str is not null"} else { println'str is null'} 执行结果还是：str is null 这样，可以把开头...
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"); // 3、创建包装对象值允许为空也可以不为空的Optional对象 Optional<String>optOfNullable1=Optional.ofNullable(null); Optional<String>optOfNullable2=Optional.ofNullable("optio...
Java字符串之间拼接时,如果有null值,则会直接拼接上null 2019-12-18 19:40 −package com.fgy.demo; public class demo06 { public static void main(String[] args) { String str1 = "aaa "; String str2 = null; String st... 糖不甜,盐不咸 ...
/*Java Program to check if a string is empty or null*/ public class Main { private static String EMPTY = ""; public static void main(String[] args) { String str1 = "Study Tonight"; System.out.println("Entered String is: "+str1); System.out.println("Is the entered string empty ...
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A third common way of checking the emptiness of String in Java is comparing it with emptyString literallike"".equals(str),this method is not as fast as the previous two but it is null safe, you don't need to check for null, in case of null it will return false.So, in my opinion...
String nullString =null; String emptyString =""; String blankString =" "; In this tutorial, we'll look athow to check if a String is Null, Empty or Blank in Java. Using the Length of the String As mentioned before, a string is empty if its length is equal to zero. We will be...
Usestr == nullto Check if a String Isnullin Java The simplest way to check if a given string isnullin Java is to compare it withnullusingstr == null. The below example illustrates this: publicclassMyClass{publicstaticvoidmain(String args[]){String str1=null;String str2="Some text";...