Question

我正在玩Generics并且在我的代码中有一个轻微的问题。我的问题是如何同时迭代两个Arraylists（没有Iterator），同时通过方法combine()中的那两个arraylists获取对象来制作一对“couple”？我已经在代码中评论了输出应该如何显示的样子。

import java.util.*;
public class Answer {

    public static void main(String[] args)
    {
        test_combine();
    }
    public static void test_combine(){
          System.out.println("TESTING COMBINE");
          ArrayList<String> theStrings = new ArrayList<String>(Arrays.asList(new String[]{"Hi","wow","Nuts"}));
          // [Hi, wow, Nuts]
          ArrayList<Integer> theInts    = new ArrayList<Integer>(Arrays.asList(new Integer[]{15, -4, 42}));
          // [15, -4, 42]
          ArrayList<Pair2<String,Integer>> stringInts = combine(theStrings,theInts);
          System.out.println(stringInts);
          // [(Hi,15), (wow,-4), (Nuts,42)]

          ArrayList<Double> theDoubs = new ArrayList<Double>(Arrays.asList(new Double[]{1.23, 42.1, 99.0, -2.1}));
          // [1.23, 42.1, 99.0, -2.1]
          ArrayList<Character> theChars = new ArrayList<Character>(Arrays.asList(new Character[]{'Z','a','!','?'}));
          // [Z, a, !, ?]
          ArrayList<Pair2<Double,Character>> doubChars = combine(theDoubs, theChars);
          System.out.println(doubChars);
          // [(1.23, Z), (42.1, a), (99.0, !), (-2.1, ?)]    
        }  



        public static <X,Y>ArrayList<Pair2<X,Y>> combine(ArrayList<X> xs, ArrayList<Y> ys)
        {
            ArrayList<Pair2<X,Y>> newValues = new ArrayList<>();

            for(int i = 0; i < xs.size() && i < ys.size(); i++)
            {
                newValues.add(xs.get(i), ys.get(i));
            }
        }
}

Answer 1

根据您发布的代码，

newValues.add(xs.get(i), ys.get(i));

应该是

newValues.add(new Pair2(xs.get(i), ys.get(i)));

假设您的Pair2有一个可以X, Y的构造函数。

如何同时迭代两个Arraylists并制作一对“夫妻”对象？

1 个答案: