Commons Collections 简明教程
Apache Commons Collections - Bag Interface
添加了新接口来支持包。包定义了一个集合，它会计算对象在集合中出现的次数。例如，如果一个包包含 {a, a, b, c}，那么 getCount("a") 将返回 2，而 uniqueSet() 将返回唯一值。
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
以下是 org.apache.commons.collections4.Bag<E> 接口的声明：
Following is the declaration for org.apache.commons.collections4.Bag<E> interface −
public interface Bag<E>
extends Collection<E>Methods
包推理的方法如下：
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
此接口继承了以下接口中的方法：
This interface inherits methods from the following interface −
-
java.util.Collectio.
Example of Bag Interface
BagTester.java 的一个示例如下：
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());
}
}