Class HandleObject
- java.lang.Object
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- org.eclipse.core.commands.common.EventManager
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- org.eclipse.core.commands.common.HandleObject
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- All Implemented Interfaces:
IIdentifiable
- Direct Known Subclasses:
NamedHandleObject
,ParameterType
public abstract class HandleObject extends EventManager implements IIdentifiable
An object that can exist in one of two states: defined and undefined. This is used by APIs that want to give a handle to an object, even though the object does not fully exist yet. This way, users can attach listeners to objects before they come into existence. It also protects the API from users that do not release references when they should.
To enforce good coding practice, all handle objects must implement
equals
andtoString
. Please usestring
to cache the result fortoString
once calculated.All handle objects are referred to using a single identifier. This identifier is a instance of
String
. It is important that this identifier remain unique within whatever context that handle object is being used. For example, there should only ever be one instance ofCommand
with a given identifier.- Since:
- 3.1
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Constructor Summary
Constructors Modifier Constructor Description protected
HandleObject(String id)
Constructs a new instance ofHandleObject
.
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Method Summary
All Methods Instance Methods Abstract Methods Concrete Methods Modifier and Type Method Description boolean
equals(Object object)
Tests whether this object is equal to another object.String
getId()
Returns the identifier for this object.int
hashCode()
Computes the hash code for this object based on the id.boolean
isDefined()
Whether this instance is defined.abstract String
toString()
The string representation of this object -- for debugging purposes only.abstract void
undefine()
Makes this object becomes undefined.-
Methods inherited from class org.eclipse.core.commands.common.EventManager
addListenerObject, clearListeners, getListeners, isListenerAttached, removeListenerObject
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Field Detail
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defined
protected transient boolean defined
Whether this object is defined. A defined object is one that has been fully initialized. By default, all objects start as undefined.
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id
protected final String id
The identifier for this object. This identifier should be unique across all objects of the same type and should never change. This value will never benull
.
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string
protected transient String string
The string representation of this object. This string is for debugging purposes only, and is not meant to be displayed to the user. This value is computed lazily, and is cleared if one of its dependent values changes.
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Constructor Detail
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HandleObject
protected HandleObject(String id)
Constructs a new instance ofHandleObject
.- Parameters:
id
- The id of this handle; must not benull
.
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Method Detail
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equals
public boolean equals(Object object)
Tests whether this object is equal to another object. A handle object is only equal to another handle object with the same id and the same class.
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getId
public final String getId()
Description copied from interface:IIdentifiable
Returns the identifier for this object.- Specified by:
getId
in interfaceIIdentifiable
- Returns:
- The identifier; never
null
.
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hashCode
public final int hashCode()
Computes the hash code for this object based on the id.
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isDefined
public final boolean isDefined()
Whether this instance is defined. A defined instance is one that has been fully initialized. This allows objects to effectively disappear even though other objects may still have references to them.- Returns:
true
if this object is defined;false
otherwise.
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toString
public abstract String toString()
The string representation of this object -- for debugging purposes only. This string should not be shown to an end user.
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undefine
public abstract void undefine()
Makes this object becomes undefined. This method should make any defined propertiesnull
. It should also send notification to any listeners that these properties have changed.
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