Container-Collections Tools (21)

Container-Collections Tools (21)

1. Collections is a tool class that provides auxiliary methods for sorting Set, List, and Map, filling, and finding elements . All methods in this class are static methods.

2. Common methods:

3. For List type container sorting process

   import java.util.ArrayList;
   import java.util.Collections;
   import java.util.List;
   
   public class CollectionsSortTest {
         
         
       public static void main(String[] args) {
         
         
           List<String> list=new ArrayList<>();
           list.add("c");
           list.add("b");
           list.add("d");
           list.add("a");
           //通过Collections工具类中的Sort方法完成排序
           Collections.sort(list);
           for (String str:list){
         
         
               System.out.println(str);
           }
       }
   }
   

4. Randomly sort List type containers , just call other methods yourself.

   import java.util.ArrayList;
   import java.util.Collections;
   import java.util.List;
   
   public class CollectionsSortTest {
         
         
       public static void main(String[] args) {
         
         
           List<String> list2=new ArrayList<>();
           list2.add("a");
           list2.add("b");
           list2.add("c");
           list2.add("d");
           //洗牌处理
           Collections.shuffle(list2);
           for (String str:list2){
         
         
               System.out.println(str);
           }
       }
   }