Is there any way to create something like this:
Map<Integer, String> barHashMap= new HashMap<Integer, String>();
barHashMap.put(1, "bar");
String[] foo = new String[]{barHashMap.values()}
foo[0] // returns "bar";
2 Answers
Get all Map values to Collection<String>. Than convert Collection<String> to String[],
Collection<String> strList=barHashMap.values();
String[] foo=strList.toArray(new String[strList.size()]);
2 Comments
Hot Licks
As I read the spec, it's not necessary to create the String[] with the "correct" size -- it's only used as a model.
Jon Skeet
@HotLicks: It's not necessary, but if you know the size easily it's slightly more efficient than passing in an array which is going to be ignored.
Call method Map.values, it return a collection Collection<V> values();
You can use the method <T> T[] toArray(T[] a) of Collection class to convert the values to Array.
Have a try with this:
Map<Integer, String> barHashMap= new HashMap<Integer, String>();
barHashMap.put(1, "bar");
==>
String[] foo = new String[barHashMap.values().size()];
barHashMap.values().toArray(foo);
Source code of method toArray of Collection is as follows:
/**
* Returns an array containing all of the elements in this collection;
* the runtime type of the returned array is that of the specified array.
* If the collection fits in the specified array, it is returned therein.
* Otherwise, a new array is allocated with the runtime type of the
* specified array and the size of this collection.
*
* <p>If this collection fits in the specified array with room to spare
* (i.e., the array has more elements than this collection), the element
* in the array immediately following the end of the collection is set to
* <tt>null</tt>. (This is useful in determining the length of this
* collection <i>only</i> if the caller knows that this collection does
* not contain any <tt>null</tt> elements.)
*
* <p>If this collection makes any guarantees as to what order its elements
* are returned by its iterator, this method must return the elements in
* the same order.
*
* <p>Like the {@link #toArray()} method, this method acts as bridge between
* array-based and collection-based APIs. Further, this method allows
* precise control over the runtime type of the output array, and may,
* under certain circumstances, be used to save allocation costs.
*
* <p>Suppose <tt>x</tt> is a collection known to contain only strings.
* The following code can be used to dump the collection into a newly
* allocated array of <tt>String</tt>:
*
* <pre>
* String[] y = x.toArray(new String[0]);</pre>
*
* Note that <tt>toArray(new Object[0])</tt> is identical in function to
* <tt>toArray()</tt>.
*
* @param a the array into which the elements of this collection are to be
* stored, if it is big enough; otherwise, a new array of the same
* runtime type is allocated for this purpose.
* @return an array containing all of the elements in this collection
* @throws ArrayStoreException if the runtime type of the specified array
* is not a supertype of the runtime type of every element in
* this collection
* @throws NullPointerException if the specified array is null
*/
<T> T[] toArray(T[] a);
barHashMap.values().toArray(new String[0])