java - java中无法动态增加数组的大小

Question

我正在尝试动态增加二维数组的大小。但是，我收到一个 Array out of Bounds 错误。下面贴出代码。在这种情况下，我尝试在某种条件下动态地将值添加到二维 vector weight[][] 。任何建议都会非常有帮助!

class perceptron {
    public static void main(String[] args) {
        int[][] myPoints = {{2,3},{4,5},{7,8},{9,10}};
        int [] classlabels = {1,1,-1,-1};
        int [] [] weight = {{0,0}};
        int base=0;
        int i,j;
        int activation=0;

        for(i=0;i<myPoints.length;i++) {
            for(j=0;j<classlabels.length;j++) {

                activation = activation+((myPoints[i][0]*weight[i][0])+(myPoints[i]
                        [1]*weight[i][1]));

                System.out.println("dot product of two vectors" + activation);
                if((activation*classlabels[j]) <= 0) {
                    System.out.println("hi");

                    weight[i+1][0] = weight[i][0]+ (classlabels[j]*myPoints[i]
                            [0]);
                    weight [i+1][1] =weight[i][1]+(classlabels[j]*myPoints[i]
                            [1]);

                    System.out.println(weight[i+1][0]);
                    System.out.println(weight[i+1][1]);

                    base = base+classlabels[j];
                    System.out.println(base);
                }
            }
        }
    }
}

Answer 1

Java 数组的大小是严格固定的。您必须使用 ArrayList。

示例:

ArrayList<ArrayList<Double>> weights = new ArrayList<>();
weights.add(new ArrayList<Double>()); // extend to be 1x0
weights.get(0).add(1.2);  //weights[0][0]=1.2
weights.get(0).add(2.3); // weights[0][1]=2.3