org.jfree.report.util
public abstract class WeakReferenceList extends Object implements Serializable, Cloneable
java.lang.ref.WeakReference
s to store its
contents. In contrast to the WeakHashtable, this list knows how to restore missing
content, so that garbage collected elements can be restored when they are accessed.
By default this list can contain 25 elements, where the first element is stored using a
strong reference, which is not garbage collected.
Restoring the elements is not implemented, concrete implementations will have to
override the restoreChild(int)
method. The getMaxChildCount
method defines the maxmimum number of children in the list. When more than
maxChildCount
elements are contained in this list, add will always return
false to indicate that adding the element failed.
To customize the list, override createReference to create a different kind of
reference.
This list is able to add or clearFromParent elements, but inserting or removing of elements is
not possible.
Constructor Summary | |
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protected | WeakReferenceList(int maxChildCount)
Creates a new weak reference list. |
Method Summary | |
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boolean | add(Object rs)
Adds the element to the list. |
protected Object | clone()
Creates and returns a copy of this object. |
Object | get(int index)
Returns the child stored at the given index. |
protected int | getChildPos(int index)
Returns the internal storage position for the child.
|
protected Object | getMaster()
Returns the master element of this list. |
protected int | getMaxChildCount()
Returns the maximum number of children in this list.
|
int | getSize()
Returns the size of the list.
|
protected boolean | isMaster(int index)
Returns true, if the given index denotes a master index of this list.
|
protected abstract Object | restoreChild(int index)
Attempts to restore the child stored on the given index.
|
void | set(Object report, int index)
Replaces the child stored at the given index with the new child which can be null.
|
Parameters: maxChildCount the maximum number of elements.
Parameters: rs the object.
Returns: true, if the object was successfully added to the list, false otherwise
will be true, and that the expression:x.clone() != x
will be true, but these are not absolute requirements. While it is typically the case that:x.clone().getClass() == x.getClass()
will be true, this is not an absolute requirement. By convention, the returned object should be obtained by calling super.clone. If a class and all of its superclasses (except Object) obey this convention, it will be the case that x.clone().getClass() == x.getClass(). By convention, the object returned by this method should be independent of this object (which is being cloned). To achieve this independence, it may be necessary to modify one or more fields of the object returned by super.clone before returning it. Typically, this means copying any mutable objects that comprise the internal "deep structure" of the object being cloned and replacing the references to these objects with references to the copies. If a class contains only primitive fields or references to immutable objects, then it is usually the case that no fields in the object returned by super.clone need to be modified. The method clone for class Object performs a specific cloning operation. First, if the class of this object does not implement the interface Cloneable, then a CloneNotSupportedException is thrown. Note that all arrays are considered to implement the interface Cloneable. Otherwise, this method creates a new instance of the class of this object and initializes all its fields with exactly the contents of the corresponding fields of this object, as if by assignment; the contents of the fields are not themselves cloned. Thus, this method performs a "shallow copy" of this object, not a "deep copy" operation. The class Object does not itself implement the interface Cloneable, so calling the clone method on an object whose class is Object will result in throwing an exception at run time.x.clone().equals(x)
Returns: a clone of this instance.
Throws: CloneNotSupportedException if the object's class does not support the
Cloneable
interface. Subclasses that
override the clone
method can also
throw this exception to indicate that an instance
cannot be cloned.
See Also: Cloneable
Parameters: index the index.
Returns: the object.
Parameters: index the index.
Returns: the internal storage index.
Returns: the master element
Returns: the maximum number of elements in this list.
Returns: the size.
Parameters: index the index.
Returns: true if the index is a master index.
Parameters: index the index.
Returns: null if the child could not be restored or the restored child.
Parameters: report the object. index the index.