java - 查找两个 ArrayList 之间的交集

Question

查找两个字符串 ArrayList 的交集。

这是代码:

public ArrayList<String> intersection( ArrayList<String> AL1, ArrayList<String> AL2){   
    ArrayList<String> empty = new ArrayList<String>();
    ArrayList<String> empty1 = new ArrayList<String>();
    if (AL1.isEmpty()){
        return AL1;
    }
    else{
        String s = AL1.get(0);
        if(AL2.contains(s))
            empty.add(s);


            empty1.addAll(AL1.subList(1, AL1.size()));
            empty.addAll(intersection(empty1, AL2));
            return empty;
    }
}

我希望输出如下所示:例如，

 [a, b, c] intersect [b, c, d, e] = [b, c]

上面的代码给了我这个输出，但我想知道如何使这个代码更容易理解。

Answer 1

你可以这样写，这样更容易理解:

/**
 * Computes the intersection of two Lists of Strings, returning it as a new ArrayList of Strings
 *
 * @param list1 one of the Lists from which to compute an intersection
 * @param list2 one of the Lists from which to compute an intersection
 *
 * @return a new ArrayList of Strings containing the intersection of list1 and list2
 */
public ArrayList<String> intersection( List<String> list1, List<String> list2) {   
    ArrayList<String> result = new ArrayList<String>(list1);

    result.retainAll(list2);

    return result;
}