J2ME in a Nutshell

Name

Hashtable

Synopsis

Hashtable is a collection class in which objects (referred to as values) are stored with associated keys. An entry is added to the Hashtable using the put() method, which takes a key and a value. Both the key and the value can be arbitrary Java objects, but neither may be null. Only one instance of each key may appear in the Hashtable; an attempt to store a second value with the same key will replace the first value. Key equality is determined by using the equals() method.

The value associated with a key can be obtained by passing the key to the get() method. If there is no value in the Hashtable with the supplied key, then null is returned. The contains() method can be used to determine whether an entry with a given key exists. The containsKey() method returns true if at least one entry with the supplied value is found in the table. Since only keys are required to be unique, it is possible for the same value (or values that are equal according to their equals() methods) to appear in the table more than once.

The size() method returns the number of entries in the Hashtable. However, to determine whether the Hashtable is empty, it is often more convienent to use the isEmpty() method.

To remove an entry from the Hashtable, pass its key to the remove() method. If an entry with the given key was found in the table, the remove() method returns its value, implementing a read-and-clear operation. All of the entries in the Hashtable can be deleted by calling the ...