Java中判断list为空(CollectionUtils.isEmpty)

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

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

        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方法检查-----------------*/ 
      
 
     
 
    
 
     
 
      
 
     
 
     
 
      

        } 
      
 
     
 
   
  
  
  

import org.springframework.util.CollectionUtils;

  
  
  

总结：

1：刚创建出来的List长度为0，但不为null

2：CollectionUtils.isEmpty()方法可以检查null和长度为0的list