ArrayIndexOutofBounds从向向量的向量添加元素的异常 [英] ArrayIndexOutofBounds Exception from Adding Element to Vector of Vectors

问题描述

我已经阅读了文档并查看了几十个SO问题，但是如果不遇到ArrayIndexOutofBounds异常，仍然无法创建向量的向量.在某些情况下，我正在创建一个矩阵，其中每个插槽都包含对边缘的引用，表示从源到目的地的飞行.遵循一个SO响应，我如下设置我的向量.

I've read the documentation and looked at scores of SO questions and still can't create a vector of vectors without running into the ArrayIndexOutofBounds exception. For some context, I am creating a matrix, where each slot contains a reference to an edge, representing a flight from a source to a destination . Following one SO response, I set up my vector as follows.

    Iterator<Edge> iter = array.iterator();
    private Vector<Vector<Edge>> matrix = new Vector<Vector<Edge>>(9);
    for (int i=0;i<9;i++){
        matrix.add(i,new Vector<Edge>(9));
    }

    while (iter.hasNext()) {
        Edge e = iter.next();
        int s = e.source; //row
        int d = e.destination; //col    
        Vector<Edge> row = matrix.get(s);
        int size = row.size();
        row.add(d, e); // Array Out of Bounds Exception
    }

我相信我已经初始化了我的内部和外部向量，并且不理解为什么向量的大小仍然为零.在开始放置和获取元素之前，是否必须将所有元素初始化为null?我将衷心感谢您的帮助.

I believe I have initialized my inner and outer vectors and don't understand why the size of the vector is still zero. Do I have to initialize all the elements to null before I can start putting and getting elements? I would really appreciate your help.

推荐答案

新Vector< Edge>(9)创建容量为9的空 Vector .因此，调用当 d 不为0时，此类 Vector 的 add(d，e)会抛出 ArrayIndexOutOfBoundsException .

new Vector<Edge>(9) creates an empty Vector of capacity 9. Therefore, calling add(d,e) for such a Vector when d is not 0 will throw ArrayIndexOutOfBoundsException.

要使用空值初始化每行 Vector ，请使用:

To initialize each row Vector with null values, use:

for (int i = 0; i < 9; i++) {
    Vector<Edge> v = new Vector<>(9);
    matrix.add(v);
    for (int j = 0; j < 9; j++)
        v.add(null);
}

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