Question

我正在尝试将一个数组排序到另外两个必须精确长度的数组。为什么运行此错误时会收到错误Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 2 at Tal.main(Tal.java:39)？我知道有更好的方法来解决这个任务，但我不被允许。我必须这样做。

public static void main(String[] args) 
{
    Scanner in = new Scanner(System.in);

    System.out.print("How many random numbers from 0 to 999? ");
    int amount = in.nextInt();

    int lowerCounter = 0;
    int higherCounter = 0;
    int[] numbers = new int[amount];
    System.out.print("Here is the random numbers: ");
    for (int i = 0; i < numbers.length; i++) 
    {
        numbers[i] = (int) Math.floor(Math.random()*1000);
        System.out.print(numbers[i] + " ");

        if (numbers[i] <= 499) {
            lowerCounter++;
        }
        else {
            higherCounter++;
        }
    }
    System.out.println("");


    int[] numbersLow = new int[lowerCounter];
    int[] numbersHigh = new int[higherCounter];
    for(int i = 0; i < numbers.length; i++)
    {
        if (numbers[i] <= 499)
        {
            numbersLow[i] = numbers[i];
        } else {
            numbersHigh[i] = numbers[i];
        }
    }

    System.out.print("These "+ lowerCounter +" numbers are from 0 to 499: ");
    for(int i = 0; i < numbersLow.length; i++) 
    {
        System.out.print(numbersLow[i] + " ");
    }

    System.out.println("");

    System.out.print("These "+ higherCounter +" numbers are from 500 to 999: ");
    for(int i = 0; i < numbersHigh.length; i++) 
    {
        System.out.print(numbersHigh[i] + " ");
    }

}

Answer 1

您的循环变量不正确。你应该修改你的代码，以便为两个数组和一个计数器提供2个不同的计数器来循环通过主数据。

lowerCounter=higherCounter=0;
for(int i = 0; i < numbers.length; i++) {
   if (numbers[i] <= 499) {
       numbersLow[lowerCounter++] = numbers[i];
   } else {
       numbersHigh[higherCounter++] = numbers[i];
   }
}

Answer 2

最好的方法是使用Java 8：

int[] lowerThan500 = Arrays.stream(numbers).filter(i -> i < 500).toArray();

代码少，错误少。

或者：

long nbLessThan500  = Arrays.stream(numbers).filter(i -> i < 500).count();

分配新数组时ArrayIndexOutOfBoundsException

2 个答案: