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New Interfaces are added to supports bags. A Bag defines a collection which, counts the number of times an object appears in the collection. For example, if a Bag contains {a, a, b, c} then getCount(“a”) will return 2 while uniqueSet() returns the unique values.
Interface Declaration
Following is the declaration for org.apache.commons.collections4.Bag<E> interface −
public interface Bag<E> extends Collection<E>
Methods
The methods for bag inference are as follows −
Sr.No. | Method & Description |
---|---|
1 |
boolean add(E object)
(Violation) Adds one copy of the specified object to the Bag. |
2 |
boolean add(E object, int nCopies)
Adds nCopies copies of the specified object to the Bag. |
3 |
boolean containsAll(Collection<?> coll)
(Violation) Returns true if the bag contains all elements in the given collection, respecting cardinality. |
4 |
int getCount(Object object)
Returns the number of occurrences (cardinality) of the given object currently in the bag. |
5 |
Iterator<E> iterator()
Returns an Iterator over the entire set of members, including copies due to cardinality. |
6 |
boolean remove(Object object)
(Violation) Removes all occurrences of the given object from the bag. |
7 |
boolean remove(Object object, int nCopies)
Removes nCopies copies of the specified object from the Bag.
|
8 |
boolean removeAll(Collection<?> coll)
(Violation) Remove all elements represented in the given collection, respecting cardinality. |
9 |
boolean retainAll(Collection<?> coll)
(Violation) Remove any members of the bag that are not in the given collection, respecting cardinality. |
10 |
int size()
Returns the total number of items in the bag across all types. |
11 |
Set<E> uniqueSet()
Returns a Set of unique elements in the Bag. |
Methods Inherited
This interface inherits methods from the following interface −
- java.util.Collectio.
Example of Bag Interface
An example of BagTester.java is as follows −
import org.apache.commons.collections4.Bag; import org.apache.commons.collections4.bag.HashBag; public class BagTester { public static void main(String[] args) { Bag<String> bag = new HashBag<>(); //add "a" two times to the bag. bag.add("a" , 2); //add "b" one time to the bag. bag.add("b"); //add "c" one time to the bag. bag.add("c"); //add "d" three times to the bag. bag.add("d",3 //get the count of "d" present in bag. System.out.println("d is present " + bag.getCount("d") + " times."); System.out.println("bag: " +bag); //get the set of unique values from the bag System.out.println("Unique Set: " +bag.uniqueSet()); //remove 2 occurrences of "d" from the bag bag.remove("d",2); System.out.println("2 occurences of d removed from bag: " +bag); System.out.println("d is present " + bag.getCount("d") + " times."); System.out.println("bag: " +bag); System.out.println("Unique Set: " +bag.uniqueSet()); } }
Output
You will see the following output −
d is present 3 times. bag: [2:a,1:b,1:c,3:d] Unique Set: [a, b, c, d] 2 occurences of d removed from bag: [2:a,1:b,1:c,1:d] d is present 1 times. bag: [2:a,1:b,1:c,1:d] Unique Set: [a, b, c, d]
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