java.util
public interface
public interface
java.util.Map
| java.util.Map |
Map has a set of keys, each key is mapped to a single value.
Nested Classes
| Map.Entry | Map.Entry is a key/value mapping which is contained in a Map. |
Known Indirect Subclasses
Summary
Public Methods
| void | clear() | ||||
| Removes all elements from this Map, leaving it empty. | |||||
| boolean | containsKey(Object key) | ||||
| Searches this Map for the specified key. | |||||
| boolean | containsValue(Object value) | ||||
| Searches this Map for the specified value. | |||||
| Set | entrySet() | ||||
Returns a Set whose elements comprise all of the mappings
that are to be found in this Map. |
|||||
| boolean | equals(Object object) | ||||
| Compares the argument to the receiver, and answers true if they represent the same object using a class specific comparison. | |||||
| V | get(Object key) | ||||
| Answers the value of the mapping with the specified key. | |||||
| int | hashCode() | ||||
| Answers an integer hash code for the receiver. | |||||
| boolean | isEmpty() | ||||
| Answers if this Map has no elements, a size of zero. | |||||
| Set | keySet() | ||||
| Answers a Set of the keys contained in this Map. | |||||
| V | put(K key, V value) | ||||
| Maps the specified key to the specified value. | |||||
| void | putAll(Map map) | ||||
| Copies every mapping in the specified Map to this Map. | |||||
| V | remove(Object key) | ||||
| Removes a mapping with the specified key from this Map. | |||||
| int | size() | ||||
| Answers the number of elements in this Map. | |||||
| Collection | values() | ||||
Returns all of the current Map values in a
Collection. |
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Details
Public Methods
public void clear()
Removes all elements from this Map, leaving it empty.
Throws
| UnsupportedOperationException | when removing from this Map is not supported |
|---|
public boolean containsKey(Object key)
Searches this Map for the specified key.
Parameters
| key | the object to search for |
|---|
Returns
- true if
keyis a key of this Map, false otherwise
public boolean containsValue(Object value)
Searches this Map for the specified value.
Parameters
| value | the object to search for |
|---|
Returns
- true if
valueis a value of this Map, false otherwise
public Set entrySet()
Returns a
Set whose elements comprise all of the mappings
that are to be found in this Map. Information on each of
the mappings is encapsulated in a separate Map.Entry instance. As
the Set is backed by this Map, users
should be aware that changes in one will be immediately visible in the
other.
Returns
- a
Setof the mappings
public boolean equals(Object object)
Compares the argument to the receiver, and answers true if they represent
the same object using a class specific comparison.
Parameters
| object | Object the object to compare with this object. |
|---|
Returns
- boolean
trueif the object is the same as this objectfalseif it is different from this object.
See Also
public V get(Object key)
Answers the value of the mapping with the specified key.
Parameters
| key | the key |
|---|
Returns
- the value of the mapping with the specified key
public int hashCode()
Answers an integer hash code for the receiver. Objects which are equal
answer the same value for this method.
Returns
- the receiver's hash
See Also
public boolean isEmpty()
Answers if this Map has no elements, a size of zero.
Returns
- true if this Map has no elements, false otherwise
See Also
public Set keySet()
Answers a Set of the keys contained in this Map. The set is backed by
this Map so changes to one are relected by the other. The set does not
support adding.
Returns
- a Set of the keys
public V put(K key, V value)
Maps the specified key to the specified value.
Parameters
| key | the key |
|---|---|
| value | the value |
Returns
- the value of any previous mapping with the specified key or null if there was no mapping
Throws
| UnsupportedOperationException | when adding to this Map is not supported |
|---|---|
| ClassCastException | when the class of the key or value is inappropriate for this Map |
| IllegalArgumentException | when the key or value cannot be added to this Map |
| NullPointerException | when the key or value is null and this Map does not support null keys or values |
public void putAll(Map map)
Copies every mapping in the specified Map to this Map.
Parameters
| map | the Map to copy mappings from |
|---|
Throws
| UnsupportedOperationException | when adding to this Map is not supported |
|---|---|
| ClassCastException | when the class of a key or value is inappropriate for this Map |
| IllegalArgumentException | when a key or value cannot be added to this Map |
| NullPointerException | when a key or value is null and this Map does not support null keys or values |
public V remove(Object key)
Removes a mapping with the specified key from this Map.
Parameters
| key | the key of the mapping to remove |
|---|
Returns
- the value of the removed mapping or null if key is not a key in this Map
Throws
| UnsupportedOperationException | when removing from this Map is not supported |
|---|
public int size()
Answers the number of elements in this Map.
Returns
- the number of elements in this Map
public Collection values()
Returns all of the current
Map values in a
Collection. As the returned Collection is
backed by this Map, users should be aware that changes in
one will be immediately visible in the other.
Returns
- a Collection of the values