Java Reference
In-Depth Information
Although the capacity will automatically increase when necessary, your program will
run more efficiently if the capacity is initially set to the number of elements you expect
will be added to the map.
The HashMap<K,V> , of course, implements all the methods in the Map<K,V> inter-
face and adds no other methods beyond constructors and an implementation of the
clone( ) method. A summary of the HashMap<K,V> constructors and clone( ) is
given in Display 16.10.
Display 16.10 Methods in the HashMap<K,V> Class
The HashMap<K,V> class is in the java.util package.
The HashMap<K,V> class extends the AbstractMap<K,V> class and implements the Map<K,V>
interface.
The HashMap<K,V> class implements all of the methods in the Map<K,V> interface (Display 16.9).
The only other methods in the HashMap<K,V> class are the constructors.
All the exception classes mentioned are the kind that are not required to be caught in a catch
block or declared in a throws clause.
All the exception classes mentioned are in the package java.lang and so do not require any
import statement.
public HashMap( )
Creates a new, empty map with a default initial capacity of 16 and load factor of 0.75.
public HashMap( int initialCapacity)
Creates a new, empty map with a default capacity of initialCapacity and load factor of 0.75.
Throws a IllegalArgumentException if initialCapacity is negative.
public HashMap( int initialCapacity, float loadFactor)
Creates a new, empty map with the specified capacity and load factor.
Throws a IllegalArgumentException if initialCapacity is negative or loadFactor nonpos-
itive.
public HashMap(Map<? extends K,? extends V> m)
Creates a new map with the same mappings as m . The initialCapacity is set to the same size
as m and the loadFactor to 0.75.
Throws a NullPointerException if m is null .
public Object clone( )
Creates a shallow copy of this instance and returns it. The keys and values are not cloned.
The remainder of the methods are the same as those described for the Map<K,V> interface
(Display 16.9.)
 
Search WWH ::




Custom Search