"线程"main"中的异常； java.lang.IndexOutOfBoundsException:索引:0，大小:0"与ArrayList? [英] "Exception in thread "main" java.lang.IndexOutOfBoundsException: Index: 0, Size: 0" with ArrayList?

问题描述

线程"main"中的异常java.lang.IndexOutOfBoundsException:索引:0，大小:0"是编译该方法时遇到的主要错误:

"Exception in thread "main" java.lang.IndexOutOfBoundsException: Index: 0, Size: 0" is the main error I get when I compile this method:

public static ArrayList<ArrayList<Integer>> createSparseArray(int len, double den) {
    int counter = 0;
    ArrayList<Integer> placeHolder = new ArrayList<Integer>();
    for (int j = 0; j < len; j++) {
        double randomNumber = Math.random();
        if (randomNumber < den) {
            counter++;
            placeHolder.add(j);
        }
    }
    ArrayList<ArrayList<Integer>> list = new ArrayList<ArrayList<Integer>>();
    for (int k = 0; k < counter; k++) {
        for (int m = 0; m < 2; m++) {
            list.get(0).set(placeHolder.get(k), (int) (Math.random() * (99999) + 1));
        }
    }
    return list;
}

我该如何解决?

推荐答案

ArrayList<ArrayList<Integer>> list在第(0)个位置中不包含任何元素，并且编译器在无法在第(0)个位置中找到任何元素时抛出超出范围的异常.指定位置.

ArrayList<ArrayList<Integer>> list doesnt contain any element in (0)th postion and the compiler throws out of bounds exception on iterating when it doesn't find any element in the specified postion.

当您尝试执行list.get(0).set(placeHolder.get(k), (int) (Math.random() * (99999) + 1));语句时，列表中不包含任何元素.您需要迭代内部列表以设置list的值.

when you try executing list.get(0).set(placeHolder.get(k), (int) (Math.random() * (99999) + 1)); statement , your list doesnt contain any element inside it. you need to iterate the inner list to set the values for the list.

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