Traversing a Map object in Java

The following is a list of some of the most commonly used Java traversal map object methods

1. Using EntrySet traversal in For-each

This is the most common way to traverse. Used when the key value is required.

new HashMap<String,String>();for(Map.Entry<String, String> entry : map.entrySet()){    System.out.println(entry.getKey()+" : "+entry.getValue());}

2. Traverse keys or values in the For-each loop

If you only need the keys or values in the map, you can implement the traversal through keyset or values instead of using EntrySet.

new HashMap<String,String>();for(String key : map.keySet()){    System.out.println("key: " + key);}for(String value : map.values()){    System.out.println("value: " + value);}

3. Using iterator traversal

new HashMap<String,String>();Iterator<Map.Entry<String, String>> iterator = map.entrySet().iterator();while(iterator.hasNext()){    Map.Entry<String, String> m = iterator.next();    " : "+m.getValue());}

Using this method to call Iterator.remove () during a time-out can remove entries, other methods cannot, and may produce unexpected results.
Reference: Links

4. Traverse value via key

new HashMap<String,String>();for(String key : map.keySet()){    String value = map.get(key);    " : " +value);}

Cases:

ImportJava.util.HashMap;ImportJava.util.Iterator;ImportJava.util.Map; Public  class T {     Public Static void Main(string[] args) {map<string, string> Map =NewHashmap<string, string> (); Map.put ("Beijing","Kaoya"); Map.put ("Henan","Hulatang"); Map.put ("Tianjin","Mahua"); System.out.println ("1, using EntrySet traversal in For-each"); for(Map.entry<string, String> entry:map.entrySet ()) {System.out.println (Entry.getkey () +" : "+ Entry.getvalue ()); } System.out.println ("2. Traverse keys or values in the For-each loop"); for(String Key:map.keySet ()) {System.out.println ("key:"+ key); } for(String value:map.values ()) {System.out.println ("Value:"+ value); } System.out.println ("3, using iterator traversal"); iterator<map.entry<string, string>> ite = Map.entryset (). Iterator (); while(Ite.hasnext ())            {map.entry<string, string> m = Ite.next (); System.out.println (M.getkey () +" : "+ M.getvalue ()); } System.out.println ("4, Traverse value through key"); for(String Key:map.keySet ())            {String value = Map.get (key); SYSTEM.OUT.PRINTLN (key +" : "+ value); }    }}

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Traversing a Map object in Java