java 一个键值对应一个数组

package test;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Set;

@SuppressWarnings("unchecked")
public class FileTest {
public static void main(String[] args) {
List list = new ArrayList();
HashMap map = new HashMap();
Set set = new HashSet();
String[] str = {"a,1","a,2","b,1","b,2","b,3","c,4"};
for(int i=0;i<str.length;i++){
String key = (String)str[i].split(",")[0];
String value = (String)str[i].split(",")[1];
if(set.contains(key)){
((HashSet)map.get(key)).add(value);
}else{
set.add(key);
Set setVal = new HashSet();
setVal.add(value);
map.put(key, setVal);
}
}
System.out.println(map);
}
}