Java Language Collection schema (set rule set)

There is a sequence of objects with no duplicate elements in the collection.

Java provides the appropriate classes and interfaces to store such elements as--set rule sets.

Here's an example to learn the set collection schema, which contains comments:

Package com.brucezhang.test;  
Import Java.util.HashSet;  
Import Java.util.Iterator;  
Import Java.util.LinkedHashSet;  
      
Import Java.util.Set;  
        public class Settest {/** * @param args */public static void main (string[] args) { The TODO auto-generated method stub//hashset is a collection structure that stores data that is not as efficient as inserting data into the order///not in sequence set<st  
              
        ring> set = new hashset<string> ();  
        Set.add ("Beijing");  
        Set.add ("Shanghai");  
        Set.add ("Hefei");  
        Set.add ("Dalian");  
        /** * Because it is a collection schema, when inserting two identical elements, only a * */Set.add ("Guangzhou") is stored;  
              
        Set.add ("Guangzhou");  
              
SYSTEM.OUT.PRINTLN (set);  
              
Iterator iterator = Set.iterator ();  
while (Iterator.hasnext ()) {//System.out.println (Iterator.next () + "");         }//For (Object element:set) {// System.out.println (element.tostring () + ""); * * * * When you need to use sequential storage, you need to use the Linkedhashset architecture, but not high efficiency * * */Set<s  
              
        tring> Set2 = new linkedhashset<string> ();  
        Set2.add ("Beijing");  
        Set2.add ("Shanghai");  
        Set2.add ("Hefei");  
        Set2.add ("Dalian");  
        /** * Because it is a collection schema, when inserting two identical elements, only a * */Set2.add ("Guangzhou") is stored;  
              
        Set2.add ("Guangzhou");  
              
System.out.println (Set2);  
              
Iterator iterator = Set.iterator ();  
while (Iterator.hasnext ()) {//System.out.println (Iterator.next () + "");  
}//For (Object Element:set2) {//System.out.println (element.tostring () + ""); //      }  
    }  
      
}

The results of the operation are as follows: