org.fest.util
Class Collections

java.lang.Object
  extended by org.fest.util.Collections

public final class Collections
extends Object

Understands utility methods related to collections.

Author:
Yvonne Wang, Alex Ruiz, Joel Costigliola

Method Summary
static
<T> Collection<T>
duplicatesFrom(Collection<T> c)
          Returns any duplicate elements from the given collection.
static
<T> List<T>
filter(Collection<?> target, CollectionFilter<T> filter)
           
static String format(Collection<?> c)
          Returns the String representation of the given collection, or null if the given collection is null.
static boolean hasOnlyNullElements(Collection<?> c)
          Returns true if the given collection has only null elements, false otherwise.
static boolean isEmpty(Collection<?> c)
          Returns true if the given collection is null or empty.
static
<T> List<T>
list(T... elements)
          Creates a list containing the given elements.
static
<T> Collection<T>
nonNullElements(Collection<T> c)
          Returns a new unmodifiable collection containing the non-null elements of the given collection.
static
<T> List<T>
nonNullElements(List<T> l)
          Returns a new unmodifiable list containing the non-null elements of the given list.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Method Detail

list

public static <T> List<T> list(T... elements)
Creates a list containing the given elements.

Type Parameters:
T - the type of elements of the list to create.
Parameters:
elements - the elements to store in the list.
Returns:
a list containing the given elements.

duplicatesFrom

public static <T> Collection<T> duplicatesFrom(Collection<T> c)
Returns any duplicate elements from the given collection.

Type Parameters:
T - the generic type of the given collection.
Parameters:
c - the given collection that might have duplicate elements.
Returns:
a collection containing the duplicate elements of the given one. If no duplicates are found, an empty collection is returned.

isEmpty

public static boolean isEmpty(Collection<?> c)
Returns true if the given collection is null or empty.

Parameters:
c - the collection to check.
Returns:
true if the given collection is null or empty, otherwise false.

filter

public static <T> List<T> filter(Collection<?> target,
                                 CollectionFilter<T> filter)

format

public static String format(Collection<?> c)
Returns the String representation of the given collection, or null if the given collection is null.

Parameters:
c - the collection to format.
Returns:
the String representation of the given collection.

nonNullElements

public static <T> Collection<T> nonNullElements(Collection<T> c)
Returns a new unmodifiable collection containing the non-null elements of the given collection. This method returns an empty unmodifiable collection if the given collection has only null elements or if it is empty. This method returns null if the given collection is null.

Type Parameters:
T - the type of elements of the collection.
Parameters:
c - the collection we want to extract non null elements from.
Returns:
a new unmodifiable collection containing the non-null elements of the given collection, or null if the given collection is null.
Since:
1.1.3

nonNullElements

public static <T> List<T> nonNullElements(List<T> l)
Returns a new unmodifiable list containing the non-null elements of the given list. This method returns an empty unmodifiable list if the given list has only null elements or if it is empty. This method returns null if the given list is null.

Type Parameters:
T - the type of elements of the list.
Parameters:
l - the list we want to extract non null elements from.
Returns:
a new unmodifiable list containing the non-null elements of the given list, or null if the given list is null.
Since:
1.1.3

hasOnlyNullElements

public static boolean hasOnlyNullElements(Collection<?> c)
Returns true if the given collection has only null elements, false otherwise. If given collection is empty, this method returns true.

Parameters:
c - the given collection. It must not be null.
Returns:
true if the given collection has only null elements or is empty, false otherwise.
Throws:
NullPointerException - if the given collection is null.
Since:
1.1.3


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