Question

我需要编写将一个数组复制到另一个数组的代码。按顺序复制所有元素

大于0，
然后连续所有元素等于0，
然后连续所有元素都小于0.

这是我尝试执行此任务失败的原因：

public static void main(String[] args)
{
    int[] arr = new int[100];
    Random random = new Random();

    for (int i = 0; i < arr.length; i++)
    {
        int randNum = random.nextInt(600) - 350;
        arr[i] = randNum;
    }
    int[] newArr = new int[100];
    for (int i = 0; i < arr.length; i++)
    {
        if (arr[i] > 0)
        {
            System.arraycopy(arr, arr[i], newArr, 0, 100);

            // arraycopy() Not works!
            // I tryed to compare each element in array greater than 0 
            // and copy it to newArr

        }
    }
    System.out.println(Arrays.toString(newArr));

为什么System.arraycopy无效？

Answer 1

看，你是每个单元格复制数组！所以内循环看起来像：

public static void main(String[] args)
{
    int[] arr = new int[100], newArr = new int[100];
    int j=0;
    Random random = new Random();

    for (int i = 0; i < arr.length; i++)
    {
        int randNum = random.nextInt(600) - 350;
        arr[i] = randNum;
    }

    for (int i = 0; i < arr.length; i++)
    {
        if (arr[i] > 0){
            newArr[j]=arr[i];
            j++;
        }
    }

    // and add code for numbers=0 and less than 0. So you should append code:
    for (int i = 0; i < arr.length; i++)
    {
        if (arr[i] == 0){
            newArr[j]=arr[i];
            j++;
        }
    }

    for (int i = 0; i < arr.length; i++)
    {
        if (arr[i] < 0){
            newArr[j]=arr[i];
            j++;
        }
    }

    System.out.println(Arrays.toString(newArr));
}

Answer 2

change_column :table_name, :column_name, 'integer USING CAST(column_name AS integer)'

如何使用某种逻辑将数组复制到另一个数组

2 个答案: