集合set的差集----求缺考的考生

package cn.cqu.huang;

import java.util.HashSet;

import java.util.Iterator;

import java.util.Set;

public class SetDemo {

	public static void main(String[] args) {

		String[] a = {"ZhangSan","LiSi","WangWu","ZhaoLiu","QianQi"};//所有考生

		String[] b = {"ZhangSan,语文，80",

					  "ZhangSan,英语，89",

					  "LiSi,数学,69",

					  "LiSi,英语,99",

					  "ZhaoLiu,数学,78"};//已经参加考试的学生成绩单

		//求哪些考生缺考

		Set<String> sa = new HashSet<String>();

		for(int i=0;i<a.length;i++){

			sa.add(a[i]);

		}

		Set<String> sb = new HashSet<String>();

		for(int i=0;i<b.length;i++){

			sb.add(b[i].split(",")[0]);

		}

		sa.removeAll(sb);  //集合的差集

		//遍历sa中剩下的元素，也即未参加考试的考生

		Iterator<String> it = sa.iterator();

		while(it.hasNext()){

			System.out.println(it.next());

		}

	}

}