具有不同 ArrayList 类型作为参数的构造函数

Question

I't first time i've occourred in this "strange" situation. I need to create two different constructor for my class:

public OpponentListAdapter(Context c, ArrayList<MyCustomObject> l){}

and

public OpponentListAdapter(Context c, ArrayList<String> l){}

because depending by type of generics of ArrayList, i need to perform different actions. But i have this error:

Method OpponentListAdapter(Context, ArrayList) has the same erasure >OpponentListAdapter(Context, ArrayList) as another method in type OpponentListAdapter

What's wrong? Maybe the solution it's simple, but for now, i can't find nothing good!

Answer 1

Both the ArrayList<String> and ArrayList<MyCustomObject> have same erasure ArrayList . Thus, both the constructors will have same signature at runtime, and hence that exception, as you have a duplicate constructor there.

If you want the constructor to take different types of ArrayList , then you can either use unbounded wildcard as in:

public OpponentListAdapter(Context c, ArrayList<?> l) {}

that will work for both the array lists, or make your constructor generic, giving a type parameter.

Answer 2

您有两个具有相同签名的构造函数，constructor1（Context，ArrayList），constructor2（Context，ArrayList），这意味着构造函数是相同的。

Answer 3

作为替代方案，您的OpponentListAdapter<\/code>可以具有public static<\/code> “创建者”方法。这看起来像这样：

public class OpponentListAdapter {

  // A constructor is not necessary but you could have one if you want
  public OpponentListAdapter(Context c, ArrayList<String> l){
    ...
  }

  //now the creator method
  public static OpponentListAdapter create(Context c, ArrayList<MyCustomObject> l){
     // implement the creation here and return it
  }

}