Java Reference
In-Depth Information
System.out.println("Map = "+nm);
}
}
TreeMap
's
toString()
method to obtain the contents of a navigable map.
When you run this application, you observe the following output:
Map = {bluejay=12, robin=19, sparrow=83}
Ascending order of keys: bluejay robin sparrow
Descending order of keys: sparrow robin bluejay
First entry = bluejay=12
Last entry = sparrow=83
Entry < ostrich is bluejay=12
Entry > crow is robin=19
Poll first entry: bluejay=12
Map = {robin=19, sparrow=83}
Poll last entry: sparrow=83
Map = {robin=19}
Utilities
TheCollectionsFrameworkwouldnotbecompletewithoutits
Arrays
and
Collec-
tions
utilityclasses.Eachclasssuppliesvariousclassmethodsthatimplementuseful
algorithms in the contexts of arrays and collections.
Following is a sampling of the
Arrays
class's array-oriented utility methods:
•
static <T> List<T> asList(T... a)
returns a fixed-size list
backed by array
a
. (Changes to the returned list “write through” to the array.)
Forexample,
List<String> birds = Arrays.asList("Robin",
"Oriole", "Bluejay");
converts the three-element array of
String
s
(recall that a variable sequence of arguments is implemented as an array) to a
List
whose reference is assigned to
birds
.
•
static int binarySearch(int[] a, int key)
searchesarray
a
forentry
key
usingthebinarysearchalgorithm(explainedfollowingthislist).
Thearraymustbesortedbeforecallingthismethod;otherwise,theresultsare
undefined. This method returns the index of the search key, if it is contained
inthearray;otherwise,(-(insertionpoint)-1)isreturned.Theinsertionpointis
