Question

我想编写一个简单的程序，要求您通过键盘输入数字（每个数字用空格或逗号分隔），然后将它们从低到高排序。

我想到的是要求用户通过键盘输入数字，将输入设置为String对象，然后通过for循环传递String，以确定字符是数字还是普通字符。如果caracter是一个数字，它将附加到一个String数组的字段并查找下一个数字并执行相同的操作，直到一个字符不是数字;在这种情况下，它会查找另一个数字并重复相同的过程，但使用下一个String数组的字段。一旦程序通过了String String的长度，String Array的每个字段都将转换为int，因此可以对其进行排序然后打印。

现在的问题是我无法打印出已排序的数字。它让我输入随机数并对它们进行排序，但它不会打印出结果。

以下是源代码：

import java.util.Scanner;

public class StartHere {
public static void main(String[] args) {

    Scanner scanner = new Scanner(System.in);
    System.out.print("Type random numbers: ");
    String input = scanner.nextLine();
    String[] numString = new String[input.length()];
    int[] numbers = new int[numString.length];
    int a = 0;
    int i = 0;

    for (i = 0; i < input.length(); i++){ // Each numString field is initialized as " ".
        numString[i] = "";
    }

    i = 0;

    while(i < (input.length() - 1)){

        if (Character.isDigit(input.charAt(a))) { // If the character at input[a] is a digit
            numString[i] += Character.toString(input.charAt(a)); // The char is appended to the numString so the hole String field can be
                                                                 // converted to an integer later.
            a++; // We go to the next character.
        }
        if ((numString[i] != null) && (!Character.isDigit(input.charAt(a)))) { // If the numString[i] field is occupped and the character
                                                                               // at input[a] is not a digit.
            i++; // We go to the next field.
        }
    }

    for (int b = 0; b < numString.length;) { // Inside this for loop each field of the numString array
                                             // is converted to an integer.
        if (numString[b] != null) {
            numbers[b] = Integer.parseInt(numString[b]);
            b++;
        } else {
            b++;
        }
    }

    quickSort(numbers, 0, numbers.length - 1); // Sorts the numbers from smaller to higher.

    for (int c = 0; c < numbers.length - 1; c++){ //
        if(c != numbers.length - 1){
            System.out.print(numbers[0] + ", ");
        }else System.out.println(numbers[c] + ".");
    }
}

public static void quickSort(int[] numbers, int left, int right) { // Defines the quickSort method.
    int pivot = numbers[left]; // We take the first element as pivot.
    int l = left; // Searches from left to right.
    int r = right; // Searches from right to left.
    int aux;

    while (l < r) { // While searches are not cross.
        while (numbers[l] <= pivot && l < r)
            l++; // Searches for an element higher than the pivot.
        while (numbers[r] > pivot)
            r--; // Searches for an element smaller than the pivot.
        if (l < r) { // If this have not been crossed.
            aux = numbers[l]; // Interchange.
            numbers[l] = numbers[r];
            numbers[r] = aux;
        }
    }
    numbers[left] = numbers[r];
    numbers[r] = pivot;
    if (left < r - 1) {
        quickSort(numbers, left, right - 1);
    }
    if (r + 1 < right) {
        quickSort(numbers, r + 1, right);
    }
} }

我该怎么办？提前谢谢！

编辑：现在我初始化了String[] numString的每个字段，这就是控制台所说的：

Exception in thread "main" java.lang.NumberFormatException: For input string: ""
at java.lang.NumberFormatException.forInputString(Unknown Source)
at java.lang.Integer.parseInt(Unknown Source)
at java.lang.Integer.parseInt(Unknown Source)
at StartHere.main(StartHere.java:34)

Answer 1

您正在打印第一个n-1次的号码：

if(c != numbers.length - 1){
    System.out.print(numbers[0] + ", "); <-- this
}else System.out.println(numbers[c] + ".");

您应该将其更改为numbers[c]

Answer 2

这个方法确实存在问题：

while(i < (input.length() - 1)) {
    if (Character.isDigit(input.charAt(a))) { 
        numString[i] += Character.toString(input.charAt(a));
        a++; // We go to the next character.
    }
    if ((numString[i] != null) && (!Character.isDigit(input.charAt(a)))) { 
        i++; // We go to the next field.
    }
}

由于您从未初始化String数组numString，执行numString[i] += Character.toString(input.charAt(a));会为null6输入6，而不仅仅是6 1}}。

您稍后尝试通过执行Integer将其解析为numbers[b] = Integer.parseInt(numString[b]);。这将抛出异常！

此外，您应该重新评估循环条件。您是否也应该从a中的input.length()中减去while(i < (input.length() - 1))？

System.out.print不起作用

2 个答案: