Java traverses the map key, the value. Ways to get the map size

Map read key-value pairs, Java traversal map two implementation methods

The first method is to get the set set of the key based on the map's keyset () method, and then traverse the map to get the value

ImportJava.util.HashMap;ImportJava.util.Iterator;ImportJava.util.Set; Public classhashmaptest2{ Public Static voidMain (string[] args) {HashMap map=NewHashMap (); Map.put ("A", "AAAA"); Map.put ("B", "BBBB"); Map.put ("C", "CCCC"); Map.put ("D", "dddd"); Set Set=Map.keyset ();  for(Iterator iter =set.iterator (); Iter.hasnext ();) {String key=(String) iter.next (); String value=(String) map.get (key); SYSTEM.OUT.PRINTLN (Key+"===="+value); } }}

The second approach is to use Map.entry to obtain:

ImportJava.util.HashMap;ImportJava.util.Iterator;ImportJava.util.Map;ImportJava.util.Set; Public classhashmaptest4{ Public Static voidMain (string[] args) {HashMap map=NewHashMap (); Map.put ("A", "AA"); Map.put ("B", "BB"); Map.put ("C", "CC"); Map.put ("D", "DD"); Set Set=Map.entryset ();  for(Iterator iter =set.iterator (); Iter.hasnext ();) {Map.entry Entry=(Map.entry) iter.next (); String Key=(String) Entry.getkey (); String value=(String) entry.getvalue (); SYSTEM.OUT.PRINTLN (Key+" :" +value); } }}

To get the map size method:

 Public Static void Main (string[] args) {    new  HashMap ();    Map.put ("Apple", "fresh Apple");     // add data to the list     map.put ("Computer", "well-equipped computer");   // add data to the list     map.put ("book", "books piled up into a mountain");     // add data to the list     System.out.println ("Map collection size is:" +map.size ());}

Java traverses the map key, the value. Ways to get the map size