A summary of the Java list Loop and the map loop _java

Summary of Java list loop and map loop

Do a list and map of the summary, there is no technical content, all the review of the API.

The test environment is under JUNIT4, and it is the same without writing a main method yourself.

First, there are three loops of the list:

   @Test public 
void Forlisttest () { 
  list<string> List = new arraylist<string> (); 
  List.add ("1"); 
  List.add ("2"); 
  List.add ("3"); 
  List.add ("4"); 
  List.add ("5"); 
 
  Iterator loops do not need to know the size and type of the collection, the best choice for 
  (@SuppressWarnings ("Rawtypes") 
  iterator iterator = List.iterator (); Iterator.hasnext ();) { 
    String list = (string) iterator.next (); 
    System.out.println (") iterator for:===============" + list); 
  } 
 
  foreach is not required to know the length of the collection for 
  (String list:list) { 
    System.out.println ("foreach:=================") relative to the for. + list); 
  } 
 
  A For loop needs to know the size of the collection and requires an ordered for 
  (int i = 0; i < list.size (); i++) { 
    System.out.println () for============= ===== "+ list.get (i)); 
  } 
} 

Then there are four loops of map:

   @Test public void Formaptest () {map<string, string> Map = new hashmap<string, string> (); 
  Map.put ("01", "1"); 
  Map.put ("02", "2"); 
  Map.put ("03", "3"); 
  Map.put ("04", "4"); 
  Map.put ("05", "5"); 
  Set<string> keyset = Map.keyset (); 
        1.keyset foreach method for (String key:keyset) {System.out.println ("1) Keyset:" + "key:" + key + "value:" 
  + map.get (key)); 
  } set<entry<string, string>> entryset = Map.entryset ();  
    2.entryset iterative method for (@SuppressWarnings ("Rawtypes") Iterator iterator = Entryset.iterator (); Iterator.hasnext ();) { 
        @SuppressWarnings ("Unchecked") entry<string, string> Entry = (entry<string, string>) iterator 
    . Next (); 
  System.out.println (") Entryset,iterator:key:" + entry.getkey () + "value:" + entry.getvalue ()); //3. Recommended, capacity Max for (entry<string, string> entry:entryset) {System.out.println (") Entryset,foreach:ke Y: "+ entry.geTKey () + "value:" + entry.getvalue ()); 
  } collection<string> values = Map.values (); 
  4. The method for only looping out the value for (String value:values) {System.out.println (") Values,just for Values,value:" + value); 
 } 
 
}

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