java map set traversal method (Processed Comparative)

Source

package com.zhaiky;

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

public class MapTest {

    public static void main(String[] args) {
        Map<String,String> map=new HashMap<String,String>();
        for(int i=0;i<50000;i++){
            map.put("key"+i, "value"+i);
        }
        String msg="";
        //通过Map.entrySet遍历key和value,最常见，效率最高
        long starttime=System.currentTimeMillis();
        for (Map.Entry<String,String> entry : map.entrySet()) {
            msg="Key = " + entry.getKey() + ", Value = " + entry.getValue();
        }
        long diffe=System.currentTimeMillis()-starttime;
        System.out.println("-----------------------------------耗时："+diffe+"毫秒");
        System.out.println(msg);
        System.out.println();
        
        By using an iterator Map.entrySet // iterator traversal key and value
        the Iterator <of Map.Entry <String, String >> entries It EnumMap.entrySet = () iterator ();.
        The while (entries.hasNext ()) {
          of Map.Entry < String, String> = entries.next entry ();
          MSG = "Key =" entry.getKey + () + ", the Value =" + entry.getValue ();
        }
        Diffe = System.currentTimeMillis () - startTime;
        the System. out.println ( "----------------------------------- Processed:" + diffe + "ms") ;
        System.out.println (MSG);
        System.out.println ();
        
        // iterate through all value map.values () but not traverse Key
        for (String value: map.values ()) {
            MSG = "the value = "+ value;
        }
        = System.currentTimeMillis Diffe () - startTime;
        System.out.println ( "--------------------------------- - Processed: "+ diffe +" msec ");
        System.out.println (MSG);
        System.out.println ();
        
        // get the value of the first key value is then worth values to key
        the Set <String> SET = map.keySet ();
        for (String Key: SET) {
            MSG = "Key =" + Key + ", the Value =" + as map.get (Key);
        }
        Diffe = System.currentTimeMillis () - startTime;
        the System.out .println ( "----------------------------------- Processed:" + diffe + "msec");
        System.out.println (MSG);
        System.out.println ();
        
    }
}
 

Test Results

----------------------------------- time: 31 ms
Key = key44663, Value = value44663

----------------------------------- time: 53 ms
Key = key44663, Value = value44663

----------------------------------- time: 68 ms
Value = value44663

----------------------------------- time: 93 ms
Key = key44663, Value = value44663