通过字段对List进行分类

public Map>> getMapList(List> result,String key){
Map>> results = new HashMap>>();
if(null != result && result.size() > 0){
for (int i = 0; i < result.size(); i++) {
HashMap rl = result.get(i);
String area = rl.get(key) == null ? "":rl.get(key).toString();
List> rls = results.get(area);
if(null != rls && rls.size() > 0){
rls.add(rl);
results.put(area, rls);
}else{
List> rls1 = new ArrayList>();
rls1.add(rl);
results.put(area,rls1);
}
}
}
return results;
}