- package Sets;
- import java.util.HashSet;
- import java.util.Iterator;
- import java.util.Set;
- import java.util.TreeSet;
- /**
- * java集合操作
- *
- * @author baby69yy2000
- *
- */
- public class Sets {
- /** 求并集 */
- public static <T> Set<T> union(Set<T> setA, Set<T> setB) {
- Set<T> setUnion;
- if (setA instanceof TreeSet)
- setUnion = new TreeSet<T>();
- else
- setUnion = new HashSet<T>();
- Iterator<T> iterA = setA.iterator();
- while (iterA.hasNext())
- setUnion.add(iterA.next());
- Iterator<T> iterB = setB.iterator();
- while (iterB.hasNext())
- setUnion.add(iterB.next());
- return setUnion;
- }
- /** 求交集 */
- public static <T> Set<T> intersection(Set<T> setA, Set<T> setB) {
- Set<T> setIntersection;
- T item;
- if (setA instanceof TreeSet)
- setIntersection = new TreeSet<T>();
- else
- setIntersection = new HashSet<T>();
- Iterator<T> iterA = setA.iterator();
- while (iterA.hasNext()) {
- item = iterA.next();
- if (setB.contains(item))
- setIntersection.add(item);
- }
- return setIntersection;
- }
- /** 求差集 */
- public static <T> Set<T> difference(Set<T> setA, Set<T> setB) {
- Set<T> setDifference;
- T item;
- if (setA instanceof TreeSet)
- setDifference = new TreeSet<T>();
- else
- setDifference = new HashSet<T>();
- Iterator<T> iterA = setA.iterator();
- while (iterA.hasNext()) {
- item = iterA.next();
- if (!setB.contains(item))
- setDifference.add(item);
- }
- return setDifference;
- }
- /**
- * 判断子集操作 判断setA中的每个元素是否也存在于setB中
- */
- public static <T> boolean subset(Set<T> setA, Set<T> setB) {
- return intersection(setA, setB).size() == setA.size();
- }
- /********************************下面是有序集的操作********************************/
- /** 求交集 */
- public static <T extends Comparable<? super T>> TreeSet<T> orderedIntersection(
- Set<T> a, Set<T> b) {
- TreeSet<T> setIntersection = new TreeSet<T>();
- Iterator<T> iterA = a.iterator(),
- iterB = b.iterator();
- T valueA, valueB;
- valueA = advance(iterA);
- valueB = advance(iterB);
- while(valueA != null && valueB != null) {
- if(valueA.compareTo(valueB) < 0)
- valueA = advance(iterA);
- else if(valueB.compareTo(valueA) < 0)
- valueB = advance(iterB);
- else {
- setIntersection.add(valueA);
- valueA = advance(iterA);
- valueB = advance(iterB);
- }
- }
- return setIntersection;
- }
- private static <T> T advance(Iterator<T> iter) {
- T value = null;
- if (iter.hasNext())
- value = iter.next();
- return value;
- }
- }
public static <T> Set<T> difference(Set<T> setA, Set<T> setB) {
Set<T> setDifference;
T item;
if (setA instanceof TreeSet) {
setDifference = new TreeSet<T>();
} else {
setDifference = new HashSet<T>();
}
// 判断一下集合的数量大小 再比较
if (setA.size() > setB.size()) {
Iterator<T> iterA = setA.iterator();
while (iterA.hasNext()) {
item = iterA.next();
if (!setB.contains(item)) {
setDifference.add(item);
}
}
} else {
Iterator<T> iterB = setB.iterator();
while (iterB.hasNext()) {
item = iterB.next();
if (!setA.contains(item)) {
setDifference.add(item);
}
}
}
return setDifference;
}