22.1-在散列集上进行集合操作

创建两个散列规则集，{“George”，"Jim"，"John"，"Blake"，"Kevin"，"Michael"} {"George"，"Katie"，"Kevin"，"Michael"，"Ryan"}求他们的并集，差集，交集。

import java.util.HashSet;
import java.util.Iterator;
import java.util.Set;

public class execise22_1 {
	public static void main(String args[]) {
		Set<String> setFirst = new HashSet<String>();
		Set<String> setSecond = new HashSet<String>();

		setFirst.add("George");
		setFirst.add("Jim");
		setFirst.add("John");
		setFirst.add("Blake");
		setFirst.add("Kevin");
		setFirst.add("Michael");

		setSecond.add("George");
		setSecond.add("Katie");
		setSecond.add("Kevin");
		setSecond.add("Michael");
		setSecond.add("Ryan");

		Set<String> union = new execise22_1().getUnion(setFirst, setSecond);

		Set<String> difference = new execise22_1().getDifference(setFirst,setSecond);

		Set<String> common = new execise22_1().getCommon(setFirst, setSecond);
		
		System.out.println(difference);
		System.out.println(union);
		System.out.println(common);

	}

	/**
	 * 求差集 
	 * 
	 * @param setFirst
	 * @param setSecond
	 * @return
	 */
	private Set<String> getDifference(Set<String> setFirst,
			Set<String> setSecond) {
		Set<String> setDifference = new HashSet<String>();

		Iterator<String> iteratorFirst = setFirst.iterator();
		while (iteratorFirst.hasNext()) {
			String temp = iteratorFirst.next();
			if (!setSecond.contains(temp)) {
				setDifference.add(temp);
			}
		}

		Iterator<String> iteratorSecond = setSecond.iterator();
		while (iteratorSecond.hasNext()) {
			String temp = iteratorSecond.next();
			if (!setFirst.contains(temp)) {
				setDifference.add(temp);
			}
		}
		return setDifference;
	}

	/**
	 * 求并集合
	 * 
	 * @param setFirst
	 * @param setSecond
	 * @return
	 */
	private Set<String> getUnion(Set<String> setFirst, Set<String> setSecond) {
		Set<String> unionSet = new HashSet<String>(setFirst);
		unionSet.addAll(setSecond);
		return unionSet;
	}
    
	/**
	 * 求交集
	 * @param setFirst
	 * @param setSecond
	 * @return
	 */
	private Set<String> getCommon(Set<String> setFirst, Set<String> setSecond) {
		Set<String> commonSet = new HashSet<String>();

		Iterator<String> iteratorFirst = setFirst.iterator();
		while (iteratorFirst.hasNext()) {
			String temp = iteratorFirst.next();
			if (setSecond.contains(temp)) {
				commonSet.add(temp);
			}
			
		}
		return commonSet;
	}
}

　　输出：

[Katie, Jim, Blake, Ryan, John]
[Katie, Jim, Blake, Ryan, John, Kevin, George, Michael]
[Kevin, George, Michael]