hashmap反转 （键值对反转）

由于HashMap中值是可以重复的，假设原Map为：

        {1=周杰伦, 2=周杰伦, 3=李健, 4=庾澄庆, 5=周杰伦, 6=谢霆锋}

我们希望得到的Map为：
        {庾澄庆=4, 周杰伦=1_2_5, 谢霆锋=6, 李健=3}

import ;

import ;
import ;
import ;

/**
 * Created by hantao5 on 2018/9/17.
 */
public class ReverseHashMap {
	@Test
	public void test() {
		Map<Integer, String> map = new HashMap();
		(1,"周杰伦");
		(2,"周杰伦");
		(3,"李健");
		(4,"庾澄庆");
		(5,"周杰伦");
		(6,"谢霆锋");
		(map);
		Map<String, String> reverseMap = new HashMap<String, String>();
		Iterator it = ().iterator();
		while (()) {
			<Integer, String> next = (<Integer, String>)();
			if ((())) {
				StringBuffer sb = new StringBuffer((()));
				("_"+());
				((),());

			} else {
				((),()+"");
			}
		}
		(reverseMap);
	}
}