Java Instance-Collection traversal

The following example shows how to traverse a collection of list, set, and map types stored as key-value pairs from the collection interface, using normal for, enhanced for, iterator, and so on to iterate through the collection:

Import Java.util.arraylist;import java.util.hashset;import Java.util.iterator;import Java.util.List;import Java.util.Set;      public class Main {public static void main (string[] args) {//List traversal listtest ();   The traversal settest () of the set set;      } private static void Settest () {set<string> Set = new hashset<string> ();      Set.add ("JAVA");      Set.add ("C");      Set.add ("C + +");      Duplicate Data add failed Set.add ("JAVA");       Set.add ("JAVASCRIPT");      Use Iterator to traverse the set set iterator<string> it = Set.iterator ();         while (It.hasnext ()) {String value = It.next ();      System.out.println (value);      }//Use the enhanced for loop to traverse the set set for (String s:set) {System.out.println (s);      }}//Traverse list collection private static void Listtest () {list<string> list = new arraylist<string> ();      List.add ("dish");      List.add ("Bird");      List.add ("teaching");      List.add ("Cheng");       List.add ("www.runoob.com"); Using Iterator traverse iterator<string> it = List.iterator ();         while (It.hasnext ()) {String value = It.next ();      System.out.println (value);         }//Use a traditional for loop to traverse for (int i = 0, size = list.size (); i < size; i++) {String value = List.get (i);      System.out.println (value);      }//Use an enhanced for loop to traverse for (String value:list) {System.out.println (value); }   }}

　　

About traversal of a collection of map types

In the following example we use HashMap's KeySet () and EntrySet () methods to iterate through the collection:

ImportJava.Util.Map;ImportJava.Util.HashMap;ImportJava.Util.HashSet;ImportJava.Util.Iterator;ImportJava.Util.List;ImportJava.Util.Set;ImportJava.Util.Map.Entry;Enhanced for LoopPublic Class Main { Public Static voidMain(String[]Args) { Creates a HashMap object and joins some key-value pairs. Map<String, String>Maps= New HashMap<String, String> ();Maps.Put("1", "PHP");Maps.Put("2", "Java");Maps.Put("3", C);Maps.Put("4", "C + +");Maps.Put("5", "HTML"); The traditional method of traversing the map set 1; KeySet () TRADITIONALMETHOD1 (maps); The traditional method of traversing the map set 2; EntrySet () TRADITIONALMETHOD2 (maps); Use the enhanced for loop to traverse the Map collection Method 1; KeySet () STRONGFORMETHOD1 (maps); Use the enhanced for loop to traverse the Map collection Method 2; EntrySet ()StrongForMethod2(Maps); } Private Static voidStrongForMethod2(Map<String, String>Maps) { Set<Entry<String, String>> Set =Maps.EntrySet(); For (Entry<String, String>Entry: Set) { StringKey=Entry.GetKey(); StringValue=Entry.GetValue(); System.Out.println(Key+ " : " +Value); } } Private Static voidStrongForMethod1(Map<String, String>Maps) { Set<String> Set =Maps.KeySet(); For (StringS: Set) { StringKey=S; StringValue=Maps.Get(S); System.Out.println(Key+ " : " +Value); } } Use the EntrySet () method to get each key-value pair in the Maps collection, Private Static voidTraditionalMethod2(Map<String, String>Maps) { Set<Map.Entry<String, String>>Sets=Maps.EntrySet(); Gets the iterator that iterates out the corresponding value. Iterator<Entry<String, String>>It=Sets.Iterator(); While (It.Hasnext()) { Map.Entry<String, String>Entry= (Entry<String, String>)It.Next(); StringKey=Entry.GetKey(); StringValue=Entry.GetValue(); System.Out.println(Key+ " : " +Value); } } Use the keyset () method to get all the keys in the Maps collection and traverse the keys to get the corresponding values. Private Static voidTraditionalMethod1(Map<String, String>Maps) { Set<String>Sets=Maps.KeySet(); Gets the iterator to traverse the corresponding value Iterator<String>It=Sets.Iterator();  while(it.Hasnext()){StringKey=it.Next();Stringvalue=Maps.Get(Key);System. out.println(Key+" : "+value);}}}

Java Instance-Collection traversal