BagUtils (Apache Commons Collections 3.2.2 API)

java.lang.Object
- org.apache.commons.collections.BagUtils

```
public class BagUtils
extends Object
```
Provides utility methods and decorators for Bag and SortedBag instances.

Since:

Commons Collections 2.1

Version:

$Revision: 972404 $ $Date: 2008-04-10 14:33:15 +0200 (Thu, 10 Apr 2008) $

Author:

Paul Jack, Stephen Colebourne, Andrew Freeman, Matthew Hawthorne

Field Summary

Fields
Modifier and Type Field and Description

static Bag EMPTY_BAG
An empty unmodifiable bag.

static Bag EMPTY_SORTED_BAG
An empty unmodifiable sorted bag.

Fields
Modifier and Type	Field and Description
`static Bag`	`EMPTY_BAG` An empty unmodifiable bag.
`static Bag`	`EMPTY_SORTED_BAG` An empty unmodifiable sorted bag.

Constructor Summary

Constructors
Constructor and Description

BagUtils()
Instantiation of BagUtils is not intended or required.

Constructors
Constructor and Description
`BagUtils()` Instantiation of BagUtils is not intended or required.

Method Summary

Methods
Modifier and Type	Method and Description
`static Bag`	`predicatedBag(Bag bag, Predicate predicate)` Returns a predicated (validating) bag backed by the given bag.
`static SortedBag`	`predicatedSortedBag(SortedBag bag, Predicate predicate)` Returns a predicated (validating) sorted bag backed by the given sorted bag.
`static Bag`	`synchronizedBag(Bag bag)` Returns a synchronized (thread-safe) bag backed by the given bag.
`static SortedBag`	`synchronizedSortedBag(SortedBag bag)` Returns a synchronized (thread-safe) sorted bag backed by the given sorted bag.
`static Bag`	`transformedBag(Bag bag, Transformer transformer)` Returns a transformed bag backed by the given bag.
`static SortedBag`	`transformedSortedBag(SortedBag bag, Transformer transformer)` Returns a transformed sorted bag backed by the given bag.
`static Bag`	`typedBag(Bag bag, Class type)` Returns a typed bag backed by the given bag.
`static SortedBag`	`typedSortedBag(SortedBag bag, Class type)` Returns a typed sorted bag backed by the given bag.
`static Bag`	`unmodifiableBag(Bag bag)` Returns an unmodifiable view of the given bag.
`static SortedBag`	`unmodifiableSortedBag(SortedBag bag)` Returns an unmodifiable view of the given sorted bag.

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

- Field Detail
  - EMPTY_BAG
```
public static final Bag EMPTY_BAG
```
    An empty unmodifiable bag.
  - EMPTY_SORTED_BAG
```
public static final Bag EMPTY_SORTED_BAG
```
    An empty unmodifiable sorted bag.
- Constructor Detail
  - BagUtils
```
public BagUtils()
```
    Instantiation of BagUtils is not intended or required. However, some tools require an instance to operate.
- Method Detail
  - synchronizedBag
```
public static Bag synchronizedBag(Bag bag)
```
    Returns a synchronized (thread-safe) bag backed by the given bag. In order to guarantee serial access, it is critical that all access to the backing bag is accomplished through the returned bag.
    It is imperative that the user manually synchronize on the returned bag when iterating over it:
```
 Bag bag = BagUtils.synchronizedBag(new HashBag());
 ...
 synchronized(bag) {
     Iterator i = bag.iterator(); // Must be in synchronized block
     while (i.hasNext())
         foo(i.next());
     }
 }
 
```
    Failure to follow this advice may result in non-deterministic behavior.
    Parameters:
    bag - the bag to synchronize, must not be null
    
    Returns:
    a synchronized bag backed by that bag
    
    Throws:
    
    IllegalArgumentException - if the Bag is null
  - unmodifiableBag
```
public static Bag unmodifiableBag(Bag bag)
```
    Returns an unmodifiable view of the given bag. Any modification attempts to the returned bag will raise an UnsupportedOperationException.
    
    Parameters:
    bag - the bag whose unmodifiable view is to be returned, must not be null
    
    Returns:
    an unmodifiable view of that bag
    
    Throws:
    
    IllegalArgumentException - if the Bag is null
  - predicatedBag
```
public static Bag predicatedBag(Bag bag,
                Predicate predicate)
```
    Returns a predicated (validating) bag backed by the given bag.
    Only objects that pass the test in the given predicate can be added to the bag. Trying to add an invalid object results in an IllegalArgumentException. It is important not to use the original bag after invoking this method, as it is a backdoor for adding invalid objects.
    
    Parameters:
    bag - the bag to predicate, must not be null
    predicate - the predicate for the bag, must not be null
    
    Returns:
    a predicated bag backed by the given bag
    
    Throws:
    
    IllegalArgumentException - if the Bag or Predicate is null
  - typedBag
```
public static Bag typedBag(Bag bag,
           Class type)
```
    Returns a typed bag backed by the given bag.
    Only objects of the specified type can be added to the bag.
    
    Parameters:
    bag - the bag to limit to a specific type, must not be null
    type - the type of objects which may be added to the bag
    
    Returns:
    a typed bag backed by the specified bag
  - transformedBag
```
public static Bag transformedBag(Bag bag,
                 Transformer transformer)
```
    Returns a transformed bag backed by the given bag.
    Each object is passed through the transformer as it is added to the Bag. It is important not to use the original bag after invoking this method, as it is a backdoor for adding untransformed objects.
    
    Parameters:
    bag - the bag to predicate, must not be null
    transformer - the transformer for the bag, must not be null
    
    Returns:
    a transformed bag backed by the given bag
    
    Throws:
    
    IllegalArgumentException - if the Bag or Transformer is null
  - synchronizedSortedBag
```
public static SortedBag synchronizedSortedBag(SortedBag bag)
```
    Returns a synchronized (thread-safe) sorted bag backed by the given sorted bag. In order to guarantee serial access, it is critical that all access to the backing bag is accomplished through the returned bag.
    It is imperative that the user manually synchronize on the returned bag when iterating over it:
```
 SortedBag bag = BagUtils.synchronizedSortedBag(new TreeBag());
 ...
 synchronized(bag) {
     Iterator i = bag.iterator(); // Must be in synchronized block
     while (i.hasNext())
         foo(i.next());
     }
 }
 
```
    Failure to follow this advice may result in non-deterministic behavior.
    Parameters:
    bag - the bag to synchronize, must not be null
    
    Returns:
    a synchronized bag backed by that bag
    
    Throws:
    
    IllegalArgumentException - if the SortedBag is null
  - unmodifiableSortedBag
```
public static SortedBag unmodifiableSortedBag(SortedBag bag)
```
    Returns an unmodifiable view of the given sorted bag. Any modification attempts to the returned bag will raise an UnsupportedOperationException.
    
    Parameters:
    bag - the bag whose unmodifiable view is to be returned, must not be null
    
    Returns:
    an unmodifiable view of that bag
    
    Throws:
    
    IllegalArgumentException - if the SortedBag is null
  - predicatedSortedBag
```
public static SortedBag predicatedSortedBag(SortedBag bag,
                            Predicate predicate)
```
    Returns a predicated (validating) sorted bag backed by the given sorted bag.
    Only objects that pass the test in the given predicate can be added to the bag. Trying to add an invalid object results in an IllegalArgumentException. It is important not to use the original bag after invoking this method, as it is a backdoor for adding invalid objects.
    
    Parameters:
    bag - the sorted bag to predicate, must not be null
    predicate - the predicate for the bag, must not be null
    
    Returns:
    a predicated bag backed by the given bag
    
    Throws:
    
    IllegalArgumentException - if the SortedBag or Predicate is null
  - typedSortedBag
```
public static SortedBag typedSortedBag(SortedBag bag,
                       Class type)
```
    Returns a typed sorted bag backed by the given bag.
    Only objects of the specified type can be added to the bag.
    
    Parameters:
    bag - the bag to limit to a specific type, must not be null
    type - the type of objects which may be added to the bag
    
    Returns:
    a typed bag backed by the specified bag
  - transformedSortedBag
```
public static SortedBag transformedSortedBag(SortedBag bag,
                             Transformer transformer)
```
    Returns a transformed sorted bag backed by the given bag.
    Each object is passed through the transformer as it is added to the Bag. It is important not to use the original bag after invoking this method, as it is a backdoor for adding untransformed objects.
    
    Parameters:
    bag - the bag to predicate, must not be null
    transformer - the transformer for the bag, must not be null
    
    Returns:
    a transformed bag backed by the given bag
    
    Throws:
    
    IllegalArgumentException - if the Bag or Transformer is null

Class BagUtils

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

EMPTY_BAG

EMPTY_SORTED_BAG

Constructor Detail

BagUtils

Method Detail

synchronizedBag

unmodifiableBag

predicatedBag

typedBag

transformedBag

synchronizedSortedBag

unmodifiableSortedBag

predicatedSortedBag

typedSortedBag

transformedSortedBag