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Chapter 17 The java.util Package |
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Dictionary
Name
DictionarySynopsis
- Class Name:
-
java.util.Dictionary
- Superclass:
-
java.lang.Object
- Immediate Subclasses:
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java.util.Hashtable
- Interfaces Implemented:
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None
- Availability:
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JDK 1.0 or later
Description
The Dictionary class is an abstract class that associates keys with values. Any non-null object can be used as a key or as a value. Key/value pairs can be stored in a Dictionary, and values can be retrieved or removed using their associated keys.
A subclass of Dictionary should use the equals() method to decide if two keys are equivalent.
Class Summary
public abstract class java.util.Dictionary extends java.lang.Object {
// Instance Methods
public abstract Enumeration elements();
public abstract Object get(Object key);
public abstract boolean isEmpty();
public abstract Enumeration keys();
public abstract Object put(Object key, Object value);
public abstract Object remove(Object key);
public abstract int size();
}
Instance Methods
elements
public abstract Enumeration elements()
- Returns
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The values in the dictionary as an Enumeration.
- Description
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This method returns an Enumeration that iterates through the values in this Dictionary.
get
public abstract Object get(Object key)
- Parameters
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- key
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The key of the value to retrieve.
- key
- Returns
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The value that corresponds to this key.
- Description
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This method returns the value that is associated with the given key.
isEmpty
public abstract boolean isEmpty()
- Returns
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true if there are no values in the Dictionary7thinsp;; false otherwise.
- Description
-
This method returns a boolean value that indicates whether or not the Dictionary is empty.
keys
public abstract Enumeration keys()
- Returns
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The keys in the dictionary as an Enumeration.
- Description
-
This method returns an Enumeration that iterates through the keys in this Dictionary.
put
public abstract Object put(Object key, Object value)
- Parameters
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- key
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A key object.
- value
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A value object.
- key
- Returns
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The previous value associated with the given key or null if key has not previously been associated with a value.
- Throws
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- NullPointerException
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If either the key or the value is null.
- NullPointerException
- Description
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This method associates the given key with the given value in this Dictionary.
remove
public abstract Object remove(Object key)
- Parameters
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- key
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The key of the value to remove.
- key
- Returns
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The value associated with the given key or null if key is not associated with a value.
- Description
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This method removes a key/value pair from this Dictionary. If the given key is not in the Dictionary, the method does nothing.
size
public abstract int size()
- Returns
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The number of keys in the Dictionary.
- Description
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This method returns the number of key/value pairs in this Dictionary.
Inherited Methods
|
Method |
Inherited From |
Method |
Inherited From |
|---|---|---|---|
|
clone() |
Object |
equals(Object) |
Object |
|
finalize() |
Object |
getClass() |
Object |
|
hashCode() |
Object |
notify() |
Object |
|
notifyAll() |
Object |
toString() |
Object |
|
wait() |
Object |
wait(long) |
Object |
|
wait(long, int) |
Object |
See Also
Enumeration, Hashtable, NullPointerException
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| Date |  |
EmptyStackException |
