Set接口实现的差集

Set接口：
main(){
String[] a={"zhang","wang","li","wu","han"};
String[] b={
"zhang,数学,88",
"zhang,语文,88",
"zhang,英语,78",
"wu,数学,99",
"wu,英语,59",
"tang,数学,77"
} 
Set<String> sa=new HashSet<String>();
for(int i=0;i<a.length;i++){
sa.add(a[i]);
}
Set<String> sb=new HashSet<String>();
sb.add(b[i].split(",")[0]);
sa.removeAll(sb);
//实现a与b的差集
System.out.println(sa);
}