Question

在这个程序中，我有一个带有高尔夫分数的文本文件，我已将每个高尔夫球手的分数添加到ArrayList中。我需要在每个ArrayList中得到这些分数的总和，以得到每个高尔夫球手的总数。

    File golf = new File("golf.txt");
    Scanner scan = new Scanner(golf);
    int i = 0;
    int parsum = 0, golfsum1 = 0, golfsum2 = 0, golfsum3 = 0, golfsum4 = 0;

    ArrayList<Integer> par = new ArrayList<Integer>();
    ArrayList<Integer> golfer1 = new ArrayList<Integer>();
    ArrayList<Integer> golfer2 = new ArrayList<Integer>();
    ArrayList<Integer> golfer3 = new ArrayList<Integer>();
    ArrayList<Integer> golfer4 = new ArrayList<Integer>();

    while (scan.hasNext()) {
        par.add(i, scan.nextInt());
        golfer1.add(i, scan.nextInt());
        golfer2.add(i, scan.nextInt());
        golfer3.add(i, scan.nextInt());
        golfer4.add(i, scan.nextInt());
        i++;
    }

    for (int j : par)
    {
        parsum += j;
    }

    for (int j : golfer1) 
    {
        golfsum1 += j;
    }
    for (int j : golfer2) 
    {
        golfsum2 += j;
    }
    for (int j : golfer3)
    {
        golfsum3 += j;
    }
    for (int j : golfer4)
    {
        golfsum4 += j;
    }

无论如何都要更快地做到这一点，而不是有5个增强的for循环

Answer 1

File golf = new File("golf.txt");
Scanner scan = new Scanner(golf);
int i = 0;
int parsum = 0, golfsum1 = 0, golfsum2 = 0, golfsum3 = 0, golfsum4 = 0;

ArrayList<Integer> par = new ArrayList<Integer>();
ArrayList<Integer> golfer1 = new ArrayList<Integer>();
ArrayList<Integer> golfer2 = new ArrayList<Integer>();
ArrayList<Integer> golfer3 = new ArrayList<Integer>();
ArrayList<Integer> golfer4 = new ArrayList<Integer>();

while (scan.hasNext()) {
    final int parValue = scan.nextInt(),
        golfValue1 = scan.nextInt(),
        golfValue2 = scan.nextInt(),
        golfValue3 = scan.nextInt(),
        golfValue4 = scan.nextInt();

    parsum += parValue;
    golfsum1 += golfValue1;
    golfsum2 += golfValue2;
    golfsum3 += golfValue3;
    golfsum4 += golfValue4;

    par.add(i, parValue);
    golfer1.add(i, golfValue1);
    golfer2.add(i, golfValue2);
    golfer3.add(i, golfValue3);
    golfer4.add(i, golfValue4);
    i++;
}

这样，您可以在扫描时直接添加并将其存储在列表中，但避免对列表进行不必要的迭代以获得总计。

Answer 2

如果您使用的是Java 8，请使用IntStream：

http://www.deadcoderising.com/2015-05-19-java-8-replace-traditional-for-loops-with-intstreams/

另外，考虑线程化每个求和任务，虽然它是高尔夫分数（琐碎，小任务），但开销可能成本过高。

如何快速对许多ArrayLists进行求和？

2 个答案: