Four ways and pros and cons of map traversal in Java

/**
* Use entries in the For-each loop to traverse
* This is the most common and, in most cases, the most desirable way to traverse. Use when key values are required
* If the traversal is an empty map, will be off the group out of Bounds, JAVA5 introduced, incompatible with the old version
* @param map
*/
public void MethodOne (Map<integer, integer> Map) {
For (Map.entry<integer, integer> entry:map.entrySet ()) {
System.out.println ("Key =" + entry.getkey () + ", Value =" + Entry.getvalue ());
}
}
/**
* Traverse keys or values in the For-each loop.
* If you only need the keys or values in the map, you can do the traversal by keyset or by values instead of EntrySet
* 10% higher efficiency than method one
*/
public void Methodtwo (MAP&LT;INTEGER,INTEGER&GT;MAP) {
Traverse key
For (Integer Key:map.keySet ()) {
System.out.println ("key =" + key);
}
Traversing values in a map
For (Integer value:map.values ()) {
System.out.println ("value =" + value);
}
}
/**
* Use iterator traversal, divided into a generic traversal, without a generic traversal
* Advantages compatible with old version, traversal can call remove Delete, For_each traversal cannot delete, traverse speed and for_each like
*/
public void Methodthreey (MAP&LT;INTEGER,INTEGER&GT;MAP) {
Iterator<map.entry<integer, integer>> entries = Map.entryset (). Iterator ();
while (Entries.hasnext ()) {
Map.entry<integer, integer> Entry = Entries.next ();
System.out.println ("Key =" + entry.getkey () + ", Value =" + Entry.getvalue ());
}
}
/**
* No iterator traversal of generic type
* @param map
*/
public void Methodthreen (map map) {
Iterator entries = Map.entryset (). Iterator ();
while (Entries.hasnext ()) {
Map.entry Entry = (map.entry) entries.next ();
Integer key = (integer) entry.getkey ();
Integer value = (integer) entry.getvalue ();
System.out.println ("key =" + key + ", value =" + value ");
}


}
/**
* Through key value traversal (low efficiency)
* Code clean, substitution of method one
*/
public void Methodfour (MAP&LT;INTEGER,INTEGER&GT;MAP) {
For (Integer Key:map.keySet ()) {
Integer value = Map.get (key);
System.out.println ("key =" + key + ", value =" + value ");
}
}

Four ways and pros and cons of map traversal in Java