[Java] Reading Map collection

Sample code to read Map collection entries.


import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;

public class ReadMap {


public static void main(String[] args) {
   Map<String, String> m = new HashMap<String,String>();
   m.put("One","Number one");
   m.put("Two","Number two");
   m.put("Three","Number three");

   long st = System.currentTimeMillis();

   //#1
   for (Map.Entry<String, String> entry : m.entrySet()) 
   {
      System.out.println(">>Key = " + entry.getKey() 
          + ", Value = " + entry.getValue());
   }
   System.out.println(">>#1 - Run time ::: " +
     (System.currentTimeMillis() - st) + "\n" );

//#2
   st = System.currentTimeMillis();
   for (String key : m.keySet()) 
   {
      String value = m.get(key);
      System.out.println(">>Key = " + key 
         + ", Value = " + value);
   }
   System.out.println(">>#2 - Run time ::: " 
      + (System.currentTimeMillis() - st)  + "\n" );


//#3
  st = System.currentTimeMillis();
for (String key : m.keySet()) 
{
System.out.println(">>Key = " + key);
}
System.out.println(">>#3 - Run time ::: " 
     + (System.currentTimeMillis() - st)  + "\n" );

  //#4 st = System.currentTimeMillis();
for (String value : m.values()) 
{
System.out.println(">>Value = " + value);
}
System.out.println(">>#4 - Run time ::: " 
     + (System.currentTimeMillis() - st)  + "\n" );

//#5
st = System.currentTimeMillis();
Iterator<Map.Entry<String, String>> iter = 
     m.entrySet().iterator();
while (iter.hasNext()) 
{
   Map.Entry<String, String> entry = iter.next();
   System.out.println(">>Key = " + entry.getKey() 
          + ", Value = " + entry.getValue());
}
System.out.println(">>#5 - Run time ::: " 
     + (System.currentTimeMillis() - st)  + "\n" );

//#6
st = System.currentTimeMillis();
Iterator iter1 = m.entrySet().iterator();
while (iter1.hasNext()) 
{
   Map.Entry entry = (Map.Entry) iter1.next();
   String key = (String)entry.getKey();
   String value = (String)entry.getValue();
   System.out.println("Key = " + key + ", Value = " + value);
}
System.out.println(">>#6 - Run time ::: " 
     + (System.currentTimeMillis() - st)  + "\n" );

}//End main method


}//End class



This is the output of the class when run.

>>Key = One, Value = Number one
>>Key = Two, Value = Number two
>>Key = Three, Value = Number three
>>#1 - Run time ::: 1

>>Key = One, Value = Number one
>>Key = Two, Value = Number two
>>Key = Three, Value = Number three
>>#2 - Run time ::: 1

>>Key = One
>>Key = Two
>>Key = Three
>>#3 - Run time ::: 0

>>Value = Number one
>>Value = Number two
>>Value = Number three
>>#4 - Run time ::: 1

>>Key = One, Value = Number one
>>Key = Two, Value = Number two
>>Key = Three, Value = Number three
>>#5 - Run time ::: 1

Key = One, Value = Number one
Key = Two, Value = Number two
Key = Three, Value = Number three

>>#6 - Run time ::: 0