Question

The method put is not applicable for the arguments

HashMap<?, ?> m = new HashMap<String, ArrayList<String>>();
ArrayList<String> l = new ArrayList<String>();
l.add("aaa");
m.put("a", l);

The method put(capture#10-of ?, capture#11-of ?) in the type HashMap<capture#10-of ?,capture#11-
of ?> is not applicable for the arguments (String, ArrayList<String>)

Answer 1

Map<String, ArrayList<String>> m = new HashMap<String, ArrayList<String>>();

追问

因为我可能要这样用
HashMap m = null;
if(是否是多个值)
{
m = new HashMap();
m.put("a", "aaa");
}
else
{
m = new HashMap>();
ArrayList l = new ArrayList();
l.add("aaa");
m.put("a", l);
}
但我不想在两个地方声明.

追答

汗。。。。。Map m=null; 试试！
Map m=new HashMap();