Question

以下循环将正确运行一次，但第二次将arraylist打印为[]。由于它是空的，当我调用getAverage方法时，我得到一个除零方法。

    for (int j = 0; j < amount_of_names*2 ; j++) {
        System.out.println(j+"J");
        ArrayList<Integer> scores = new ArrayList<Integer>();
        // get arraylist of next series
        scores = readNextSeries(Scannerb);
        System.out.println(scores+"here");
        scores.remove(scores.size()-1);
        // get mean
        int average = getAverage(scores);
        System.out.println(average + "is" + scores);
        // put arraylist of next series in total arraylist
        combiner(scores);
        //remove all elements in temp scores array
        scores.clear();
        System.out.println(scores);
    }


the output is: Enter a read file: input.txt
5
0J
[88, 92, 78]readnextseries
[88, 92, 78]here
86is[88, 92, 78]
[]
1J
[]readnextseries
[]here
Exception in thread "main" java.lang.ArithmeticException: / by zero

getAverage代码：

private static int getAverage(ArrayList<Integer> inList) {
    int total = 0;
    // sum all arraylist elemtents
    for (int score : inList) {
        total += score;
    }
    // average is total/number of scores
    int average = total / inList.size();
    return average;
}

获取系列代码：

private static ArrayList<Integer> readNextSeries(Scanner Scannerb) {
    ArrayList<Integer> score = new ArrayList<Integer>();

    // store player name in names ArrayList
    names.add(Scannerb.nextLine());
    // repeat this process until -1 is read
    while (Scannerb.hasNextInt()) {
        // grab next Integer
        int test = Scannerb.nextInt();
        // if Integer is positive
        if (test > 0) {
            // add integer to score arrayList
            score.add(test);
            // if Integer is negative
        } else if (test == -1) {
            // add a -1 to the arrayList; Marks each Player's scores
            score.add(-1);
            break;
        } else {
            System.out.println("SomethingWenTWrong");
        }
    }
    System.out.println(score+"readnextseries");
    return score;
}

pastebin：http://pastebin.com/qhGr3JCr

Answer 1

要在运行时避免异常，只需在此之前进行检查 -

if(d != 0){
   int result = someNumber/d;
}

Answer 2

显然，似乎readNextSeries（Scannerb）方法在第二轮中返回一个空数组。实际上，随后调用System.out.println会打印并清空数组。您应该发布代码的其他部分以供进一步调查。

ArrayList问题Java，空白数组第二次循环

2 个答案: