Four methods in java traversal Map

All in java implement map Map interface, so all Map (eg HashMap, TreeMap, LinkedHashMap, Hashtable, etc.) can be used in the following manner to traverse.

• Method a: Map traversal using entries in a for loop:

/ ** 
* The most common and most used in most cases, generally require the use of key-value pairs 
 * / 
the Map <String, String> = new new HashMap the Map <String, String> (); 
map.put ( "Bear large "," brown "); 
map.put (" bears two "," yellow "); 
for (of Map.Entry <String, String> entry: EnumMap.entrySet ()) { 
    String MapKey entry.getKey = (); 
    entry.getValue mapValue = String (); 
    System.out.println (MapKey + ":" + mapValue); 
}

• Method two: traversing key or values ​​in a for loop, only generally applicable to key in the map, or using the value, the better in performance than entrySet;

Map <String,String>map = new HashMap<String,String>();
map.put("熊大", "棕色");
map.put("熊二", "黄色");
//key
for(String key : map.keySet()){
    System.out.println(key);
}
//value
for(String value : map.values()){
    System.out.println(value);
}

• Method three: The Iterator traversal;

Iterator<Entry<String, String>> entries = map.entrySet().iterator();
while(entries.hasNext()){
    Entry<String, String> entry = entries.next();
    String key = entry.getKey();
    String value = entry.getValue();
    System.out.println(key+":"+value);
}

• Method four: traversing through the key value to find, in this way the efficiency is relatively low, because the operation itself is time-consuming from the key value;

for(String key : map.keySet()){
    String value = map.get(key);
    System.out.println(key+":"+value);
}