Question

基本上，我的作业需要我取一个字符串数组和一个字符串搜索词，并返回数组中搜索词的位置（如果没有找到则返回-1）并取一个字符串和气泡数组解决。我收到的错误似乎只是泡泡排序，我不明白为什么。

我收到的错误消息是：

Exception in thread "main" java.lang.NullPointerException
at java.lang.String$CaseInsensitiveComparator.compare(String.java:1193)
at java.lang.String$CaseInsensitiveComparator.compare(String.java:1186)
at java.lang.String.compareToIgnoreCase(String.java:1239)
at mmtextreader.MMTextReader.bubbleSort(MMTextReader.java:100)
at mmtextreader.MMTextReader.main(MMTextReader.java:47)

代码：

public class TextReader {

    /**
     * @param args the command line arguments
     * @throws java.io.FileNotFoundException
     */
    public static void main(String[] args) throws FileNotFoundException {
        // TODO code application logic here

        String[] Array;

        Array = wordPut("beowulf.txt");

        Scanner reader = new Scanner(System.in);

        System.out.println("Input word: ");

        String term = reader.next();

        int position = pFind(Array, term);

        if(position == -1) {
            System.out.println("no word found");
        } else {
            System.out.println(term + " is found at " + (position+1));
        }

        bubbleSort(Array);
    }

    public static String[] wordPut(String s) throws FileNotFoundException {
        String[] Array = new String[50000];

        Scanner reader = new Scanner(new BufferedReader(new FileReader(s))).useDelimiter("[^\\p{Alpha}']+");

        int wordcount = 0;
        while (reader.hasNext()) {
            Array[wordcount] = reader.next();
            wordcount++;
        }
        for (int i = 0; i < Array.length; i++) {
            if (Array[i] != null) {
                System.out.println(Array[i]);
            }
        }

        return Array;
    }

    public static String[] bubbleSort(String[] a) {
        int lElement = a.length - 1;
        boolean t = true;
        for (int i = 0; i <= a.length - 1; i++) {

            boolean swap = false;

            for (int j = 0; j < lElement; j++) {
                if (a[j].compareTo(a[j + 1]) > 0) {
                    String store = a[j];
                    a[j] = a[j + 1];
                    a[j + 1] = store;
                    swap = true;
                }
            }
            lElement--;
            if (swap == false) {
                break;
            }
        }
        for(int n = 0; n < a.length; n++) {
            System.out.println(a[n]);
        }
        return a;
    }

    public static int pFind(String[] a, String trm) {
        int pos = -1;
        for (int i = 0; i < a.length; i++) {
            if (a[i].compareToIgnoreCase(trm) == 0) {
                pos = i;
                break;
            }
        }
        return pos;
    }

}

Answer 1

OK！我检查了你的代码，你唯一的问题是你将你的数组理解为大小为5000，这是wordPut（）方法中的问题

  String[] Array = new String[50000];

我在计算机上尝试了你的代码，工作正常，但是buble排序很顺利，除了数组的声明，试着找出数组的大小然后声明！

冒泡排序作业时出错

1 个答案: