Java中判斷list為空(CollectionUtils.isEmpty)

Java中判斷list為空(CollectionUtils.isEmpty)
https://blog.csdn.net/zhuoya_/article/details/104621126

   
   
   
           
 
            
 
             
 
              
 
             
 
             
 
              
 
               @Test 
              
 
             
 
            
 
             
 
              
 
             
 
             
 
              
 
               public 
               void 
               testStr 
               () { 
              
 
             
 
            
 
             
 
              
 
             
 
             
 
              
 
               /*----------------【Start】isEmpty方法檢查-----------------*/ 
              
 
             
 
            
 
             
 
              
 
             
 
             
 
              

                List<String> strList1 = Lists.newArrayList(); 
              
 
             
 
            
 
             
 
              
 
             
 
             
 
              

                System.out.println(CollectionUtils.isEmpty(strList1)); 
               //true 
              
 
             
 
            
 
             
 
              
 
             
 
             
 
              

                System.out.println(CollectionUtils.isEmpty( 
               new 
               ArrayList())); 
               //true 
              
 
             
 
            
 
             
 
              
 
             
 
             
 
              

                System.out.println(strList1 == 
               null); 
               //false 
              
 
             
 
            
 
             
 
              
 
             
 
             
 
              

                System.out.println(strList1.size()); 
               //0 
              
 
             
 
            
 
             
 
              
 
             
 
             
 
              
 
              
 
             
 
            
 
             
 
              
 
             
 
             
 
              

                List<String> strList2 = 
               new 
               ArrayList<>(); 
              
 
             
 
            
 
             
 
              
 
             
 
             
 
              

                System.out.println(strList2 == 
               null); 
               //false 
              
 
             
 
            
 
             
 
              
 
             
 
             
 
              

                strList2= 
               null; 
              
 
             
 
            
 
             
 
              
 
             
 
             
 
              

                System.out.println(strList2 == 
               null); 
               //true 
              
 
             
 
            
 
             
 
              
 
             
 
             
 
              

                System.out.println(CollectionUtils.isEmpty(strList2)); 
               //true 
              
 
             
 
            
 
             
 
              
 
             
 
             
 
              
 
               /*----------------【END】isEmpty方法檢查-----------------*/ 
              
 
             
 
            
 
             
 
              
 
             
 
             
 
              

                } 
              
 
             
 
           
  
  
  
          

import org.springframework.util.CollectionUtils;

  
  
  
          

總結：

1：剛創建出來的List長度為0，但不為null

2：CollectionUtils.isEmpty()方法可以檢查null和長度為0的list