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java.util
Class Collections.EmptyMap  

java.lang.Object
  java.util.AbstractMap
      java.util.Collections.EmptyMap

All Implemented Interfaces:

Map, java.io.Serializable

Enclosing class:

Collections

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private static final class Collections.EmptyMap

extends AbstractMap

implements java.io.Serializable

The implementation of Collections.EMPTY_MAP 55 . This class name is required for compatibility with Sun's JDK serializability.

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Nested Class Summary

 

Nested classes inherited from class java.util.AbstractMap

AbstractMap.BasicMapEntry

 

Nested classes inherited from class java.util.Map

Map.Entry

 

Field Summary
private static long	serialVersionUID           Compatible with JDK 1.4.

 

Fields inherited from class java.util.AbstractMap

ENTRIES, keys, KEYS, values, VALUES

 

Constructor Summary
(package private)	Collections.EmptyMap()           A private constructor adds overhead.

 

Method Summary
boolean	containsKey(java.lang.Object key)           No entries!
boolean	containsValue(java.lang.Object value)           No entries!
Set	entrySet()           There are no entries.
boolean	equals(java.lang.Object o)           Equal to all empty maps.
java.lang.Object	get(java.lang.Object o)           No mappings, so this returns null.
int	hashCode()           The hashcode is always 0.
Set	keySet()           No entries.
java.lang.Object	remove(java.lang.Object o)           Remove always succeeds, with null result.
int	size()           Size is always 0.
java.lang.String	toString()           The string never changes.
Collection	values()           No entries.

 

Methods inherited from class java.util.AbstractMap

clear, clone, equals, hashCode, isEmpty, put, putAll

 

Methods inherited from class java.lang.Object

finalize, getClass, notify, notifyAll, wait, wait, wait

 

Field Detail

serialVersionUID

private static final long serialVersionUID

Compatible with JDK 1.4.

See Also:

Constant Field Values

Constructor Detail

Collections.EmptyMap

Collections.EmptyMap()

A private constructor adds overhead.

Method Detail

entrySet

public Set entrySet()

There are no entries.

Specified by:

entrySet in interface Map

Specified by:

entrySet in class AbstractMap

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containsKey

public boolean containsKey(java.lang.Object key)

No entries!

Specified by:

containsKey in interface Map

Overrides:

containsKey in class AbstractMap

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containsValue

public boolean containsValue(java.lang.Object value)

No entries!

Specified by:

containsValue in interface Map

Overrides:

containsValue in class AbstractMap

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equals

public boolean equals(java.lang.Object o)

Equal to all empty maps.

Specified by:

equals in interface Map

Overrides:

equals in class AbstractMap

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get

public java.lang.Object get(java.lang.Object o)

No mappings, so this returns null.

Specified by:

get in interface Map

Overrides:

get in class AbstractMap

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hashCode

public int hashCode()

The hashcode is always 0.

Specified by:

hashCode in interface Map

Overrides:

hashCode in class AbstractMap

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keySet

public Set keySet()

No entries.

Specified by:

keySet in interface Map

Overrides:

keySet in class AbstractMap

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remove

public java.lang.Object remove(java.lang.Object o)

Remove always succeeds, with null result.

Specified by:

remove in interface Map

Overrides:

remove in class AbstractMap

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size

public int size()

Size is always 0.

Specified by:

size in interface Map

Overrides:

size in class AbstractMap

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values

public Collection values()

No entries. Technically, EMPTY_SET, while more specific than a general Collection, will work. Besides, that's what the JDK uses!

Specified by:

values in interface Map

Overrides:

values in class AbstractMap

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toString

public java.lang.String toString()

The string never changes.

Overrides:

toString in class AbstractMap

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Overview  Package   Class  Use  Deprecated  Index
Home >> All >> java >> [ util overview ]	PREV CLASS  NEXT CLASS
SUMMARY:  JAVADOC |  SOURCE |  DOWNLOAD | NESTED | FIELD | CONSTR | METHOD	DETAIL: FIELD | CONSTR | METHOD

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