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Enumerations (NetBeans Utilities API) - NetBeans API Javadoc 5.5.0

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org.openide.util
Class Enumerations

java.lang.Object
  org.openide.util.Enumerations

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public final class Enumerations
extends Object

Factory methods for various types of Enumeration. Allows composition of existing enumerations, filtering their contents, and/or modifying them. All of this is designed to be done lazily, i.e. elements created on demand.

Since:

4.37

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Nested Class Summary
static interface	Enumerations.Processor           Processor interface that can filter out objects from the enumeration, change them or add aditional objects to the end of the current enumeration.

 

Method Summary
static Enumeration	array(Object[] arr)           Returns an enumeration that iterates over provided array.
static Enumeration	concat(Enumeration enumOfEnums)           Concatenates the content of many enumerations.
static Enumeration	concat(Enumeration en1, Enumeration en2)           Concatenates the content of two enumerations into one.
static Enumeration	convert(Enumeration en, Enumerations.Processor processor)           For each element of the input enumeration en asks the Enumerations.Processor to provide a replacement.
static Enumeration	empty()           An empty enumeration.
static Enumeration	filter(Enumeration en, Enumerations.Processor filter)           Filters some elements out from the input enumeration.
static Enumeration	queue(Enumeration en, Enumerations.Processor filter)           Support for breadth-first enumerating.
static Enumeration	removeDuplicates(Enumeration en)           Filters the input enumeration to new one that should contain each of the provided elements just once.
static Enumeration	removeNulls(Enumeration en)           Removes all nulls from the input enumeration.
static Enumeration	singleton(Object obj)           Creates an enumeration with one element.

 

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

 

Method Detail

empty

public static final Enumeration empty()

An empty enumeration. Always returns false from empty().hasMoreElements() and throws NoSuchElementException from empty().nextElement().

Returns:

the enumeration

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singleton

public static Enumeration singleton(Object obj)

Creates an enumeration with one element.

Parameters:

obj - the element to be present in the enumeration.

Returns:

enumeration

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concat

public static Enumeration concat(Enumeration en1,
                                 Enumeration en2)

Concatenates the content of two enumerations into one. Until the end of en1 is reached its elements are being served. As soon as the en1 has no more elements, the content of en2 is being returned.

Parameters:

en1 - first enumeration

en2 - second enumeration

Returns:

enumeration

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concat

public static Enumeration concat(Enumeration enumOfEnums)

Concatenates the content of many enumerations. The input value is enumeration of Enumeration elements and the result is composed all their content. Each of the provided enumeration is fully read and their content returned before the next enumeration is asked for their elements.

Parameters:

enumOfEnums - Enumeration of Enumeration elements

Returns:

enumeration

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removeDuplicates

public static Enumeration removeDuplicates(Enumeration en)

Filters the input enumeration to new one that should contain each of the provided elements just once. The elements are compared using their default equals and hashCode methods.

Parameters:

en - enumeration to filter

Returns:

enumeration without duplicated items

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array

public static Enumeration array(Object[] arr)

Returns an enumeration that iterates over provided array.

Parameters:

arr - the array of object

Returns:

enumeration of those objects

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removeNulls

public static Enumeration removeNulls(Enumeration en)

Removes all nulls from the input enumeration.

Parameters:

en - enumeration that can contain nulls

Returns:

new enumeration without null values

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convert

public static Enumeration convert(Enumeration en,
                                  Enumerations.Processor processor)

For each element of the input enumeration en asks the Enumerations.Processor to provide a replacement. The toAdd argument of the processor is always null.

Example to convert any objects into strings:

 Processor convertToString = new Processor() {
     public Object process(Object obj, Collection alwaysNull) {
         return obj.toString(); // converts to string
     }
 };
 Enumeration strings = Enumerations.convert(elems, convertToString);
 

Parameters:

en - enumeration of any objects

processor - a callback processor for the elements (its toAdd arguments is always null)

Returns:

new enumeration where all elements has been processed

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filter

public static Enumeration filter(Enumeration en,
                                 Enumerations.Processor filter)

Filters some elements out from the input enumeration. Just make the Enumerations.Processor return null. Please notice the toAdd argument of the processor is always null.

Example to remove all objects that are not strings:

 Processor onlyString = new Processor() {
     public Object process(Object obj, Collection alwaysNull) {
         if (obj instanceof String) {
             return obj;
         } else {
             return null;
         }
     }
 };
 Enumeration strings = Enumerations.filter(elems, onlyString);
 

Parameters:

en - enumeration of any objects

filter - a callback processor for the elements (its toAdd arguments is always null)

Returns:

new enumeration which does not include non-processed (returned null from processor) elements

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queue

public static Enumeration queue(Enumeration en,
                                Enumerations.Processor filter)

Support for breadth-first enumerating. Before any element is returned for the resulting enumeration it is processed in the Enumerations.Processor and the processor is allowed to modify it and also add additional elements at the (current) end of the queue by calling toAdd.add or toAdd.addAll. No other methods can be called on the provided toAdd collection.

Example of doing breadth-first walk through a tree:

 Processor queueSubnodes = new Processor() {
     public Object process(Object obj, Collection toAdd) {
         Node n = (Node)obj;
         toAdd.addAll (n.getChildrenList());
         return n;
     }
 };
 Enumeration strings = Enumerations.queue(elems, queueSubnodes);
 

Parameters:

en - initial content of the resulting enumeration

filter - the processor that is called for each element and can add and addAll elements to its toAdd Collection argument and also change the value to be returned

Returns:

enumeration with the initial and queued content (it can contain null if the filter returned null from its Enumerations.Processor.process(java.lang.Object, java.util.Collection) method.

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