Question

我有一个ArrayList，里面填充了Result类的对象。每个结果都有一个名为Category的属性。

我正在尝试使用for循环创建方法，该方法使用来自用户的输入类别打印出每个结果。

目前for循环有效，但if-statement分隔是否打印出结果不起作用，这就是我正在搜索的帮助。

自从我尝试了所有其他代码以来，单独使用if语句是我认为目前无效的。

String categoryToPrint;
    System.out.println("Which category would you like to print out results for?");
    categoryToPrint = scanner.nextLine();
    categoryToPrint = normalisera(grenAttVisa); //method making all letters small and first letter capital.
    System.out.println("Resultlist for" + categoryToPrint );
    for (int i = 0; i < resultlist.size(); i++) {
        Athlete matched = null;
        Result res = resultlist.get(i);


        if (res.categoryName().equals(categoryToPrint)) {


        for (int x = 0; x < resultlist.size(); x++) {
            Athlete del = athletes.get(x);
            if (res.athleteStartNumber() == del.startNumber()) {
                matched = del;
                break;
            }
        }
        System.out.println(matched.surName() + " " + matched.lastName() + " has the result: " + res.categoryValue());
    }
    }

Answer 1

更改

for (int x = 0; x < resultlist.size(); x++)

到

for (int x = 0; x < athletes.size(); x++)

让我们暂时考虑一下这种情况：

resultlist = [result1, result2, result3] // size() == 3

athletes = [athlete1, athlete2] // size() == 2

依靠您的实际代码：

for (int i = 0; i < resultlist.size(); i++) {
    for (int x = 0; x < resultlist.size(); x++) {
        Athlete del = athletes.get(x);
        ...

以下是外循环第一次迭代中内循环的方法：

resultlist.size() == 3
i == 0, x == 0 ====> Athlete del = athletes.get(0); // x < 3, good
i == 0, x == 1 ====> Athlete del = athletes.get(1); // x < 3, good
i == 0, x == 2 ====> Athlete del = athletes.get(2); // x < 3, good but the athletes arraylist has only 2 elements, Exception raised

循环使用ArrayList并仅打印出具有特定属性的对象

1 个答案: