"JAVA" HashMap Getting Started to abort: using HashMap

Absrtact: As the beginning of HashMap series of learning notes, I think we should familiarize myself with HashMap's usage scene first.

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Map is essentially a data structure belonging to a collection type.

The following code snippet illustrates the common operation of Map (curd) and takes care to traverse the map as much as possible using the entry method.

1Hashmap<string, double> scores =NewHashmap<>();2 3Scores.put ("Sam", 100.0);4Scores.put ("Jacky", 50.0);5Scores.put ("Tim", 80.0);6 7 System.out.print (scores);8 9Scores.put ("Tim", 100.0);Ten System.out.print (scores); One System.out.print (scores.tostring ()); A  -System.out.print (Scores.get ("Sam")); -  theSystem.out.println (Scores.containskey ("Sam")); -System.out.println (Scores.containsvalue (100.0)); -          -         //Traverse, cost more time +Iterator<string> it =Scores.keyset (). iterator (); -          while(It.hasnext ()) { +String tmp =It.next (); A SYSTEM.OUT.PRINTLN (TMP); at System.out.println (Scores.get (TMP)); -         } -  -System.out.println ("Count of student:" +scores.size ()); -SYSTEM.OUT.PRINTLN ("scores is" + (Scores.isempty ()? " Empty ":" Not Empty ")); -  in         //Traverse and delete target, cost less -iterator<map.entry<string, double>> begit =Scores.entryset (). iterator (); to          for(; Begit.hasnext ();) { +map.entry<string, double> item =Begit.next (); -  the             if(Item.getvalue () = = 100.0) { * Begit.remove (); $             }Panax Notoginseng         } -  the System.out.println (scores); +  A scores.clear (); theSYSTEM.OUT.PRINTLN (scores);

The output is as follows:

{tim=80.0, jacky=50.0, sam=100.0} {tim=100.0, jacky=50.0, sam=100.0} {tim=100.0, jacky=50.0, sam=100.0}100.0true
True
Tim
100.0
Jacky
50.0
Sam
100.0
Count of Student:3
Scores is not empty
{jacky=50.0}
{}

PS: The actual project HashMap with a few, complex operations (such as key HashMap) do not do a demonstration.

"JAVA" HashMap Getting Started to abort: using HashMap