Java Reference
In-Depth Information
String[] fruits = {"apples", "pears", "grapes", "ba-
nanas", "kiwis"};
int[] quantities = {10, 15, 8, 17, 30};
for (int i = 0; i < fruits.length; i++)
msi.put(fruits[i], quantities[i]);
for
(Map.Entry<String,
Integer>
entry:
msi.entrySet())
System.out.println(entry.getKey()+":
"+entry.getValue());
}
}
When you run this application, it generates the following output:
apples: 10
bananas: 17
grapes: 8
kiwis: 30
pears: 15
HashMap
The
HashMap
class provides a map implementation that is based on a hashtable data
structure. This implementation supports all
Map
operations, and permits null keys and
null values. It makes no guarantees on the order in which entries are stored.
A hashtable maps keys to integer values with the help of a
hash function
. Java
provides this function in the form of
Object
's
hashCode()
method, which classes
override to provide appropriate hash codes.
A
hash code
identifies one of the hashtable's array elements, which is known as a
bucket
or
slot
. For some hashtables, the bucket may store the value that is associated
with the key.
Figure 5-3
illustrates this kind of hashtable.
