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Comparator sort functional interface

2022-06-24 13:06:00 【51CTO】

Comparator Is a functional interface , This function is mainly used to customize sorting rules , Other functions are not recorded here , Just record how you sort ：

The current common sorting methods ：

Array sorting 、 Collection sorting 、 Convert collection to stream sort

       
       public 
       
       class 
       
       sortTest {
       
       public 
       
       static 
       
       void 
       
       main(
       
       String[] 
       
       args) {
       
       List
       
       <
       
       User
       
       > 
       
       usersList 
       
       = 
       
       new 
       
       ArrayList
       
       <>(){
       
            {
       
       for(
       
       int 
       
       i 
       
       = 
       
       0; 
       
       i 
       
       < 
       
       3; 
       
       i 
       
       ++) {
       
       add(
       
       new 
       
       User(
       
       "lxc"
       
       +
       
       i, 
       
       20
       
       +
       
       i));
       
                }
       
            }
       
        };
       
       //  Mode one  ->  Array utility class ：Arrays.sort(T[] a, Comparator<? super T> c);
       
       //  Mode two  ->  A collection of stream() Method ：new ArrayList<>().stream().sorted(Comparator<? super T> comparator);
       
       //  Mode two  ->  Collection tool class ：
       
       Collections.
       
       sort(
       
       usersList, 
       
       new 
       
       Comparator
       
       <
       
       User
       
       >() {
       
       @Override
       
       public 
       
       int 
       
       compare(
       
       User 
       
       o1, 
       
       User 
       
       o2) {
       
       //  In reverse order 
       
       return 
       
       o2.
       
       getAge() 
       
       - 
       
       o1.
       
       getAge();
       
       //  positive sequence 
       
       return 
       
       o1.
       
       getAge() 
       
       - 
       
       o2.
       
       getAge();
       
            }
       
        });
       
       System.
       
       out.
       
       println(
       
       JSON.
       
       toJSONString(
       
       usersList, 
       
       SerializerFeature.
       
       PrettyFormat));
       
    }
       
}
      
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Comparator Sort functional interface _json

Cases in actual development ：

If the front and back ends are separated from the frame , The front desk excel When downloading template , The backend is actually a new one excel, Then fill in the data , internals ： Get every field in the entity class to be exported through reflection , Add to list In the list , Loop traversal list list , The with @Excel Annotated fields and @Excel Attributes in the annotation are added to One Object[] Go to... In the array , And then put Object[] Array added to fields Go to... In the list , Finally, convert the list into a stream , Sort .

Comparator Sort functional interface _java_02