Question

我有一个程序，我在计算字符串中的单词数。问题是，我需要我的while循环运行一定次数。每次运行时，我都会创建一个子字符串来切断第一个单词。

程序：

public class WordCount {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        String sentence = "My name is Brad";
        int pos;
        String word;
        String newSent;
        int wordCount = 0;

        while(sentence.length() >= 0){
            pos = sentence.indexOf(' ');
            word = sentence.substring(0,pos);
            newSent = sentence.substring(pos+1);
            sentence = newSent;

            wordCount++;

            System.out.println("word = " + word);
            System.out.println("newSent = " + newSent);
            System.out.println("wordCount = " + wordCount);
        }
    }

问题是永远不会计算最后一个词，因为错误发生时就是这样。

输出：

word = My
newSent = name is Brad
wordCount = 1
word = name
newSent = is Brad
wordCount = 2
word = is
newSent = Brad
wordCount = 3
Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: -1
    at java.lang.String.substring(Unknown Source)
    at assignment3.WordCount.main(WordCount.java:18)

更新

pos = sentence.indexOf(' ');
word = sentence.substring(0,pos);
newSent = sentence.substring(pos+1);
sentence = newSent;
if (sentence.indexOf(' ') == -1){
    newSent = "";
    word = sentence;
}
if (word.length() >= minLength){
    wordCount++;
}

编辑2：我的解决方案是任何人都很好奇

public static void main(String[] args) {
        // TODO Auto-generated method stub
        String sentence = "My name is Brad";
        int pos;
        String word;
        String newSent;
        int minLength = 0;
        int wordCount = 0;

        // sentence.indexOf(' ') != -1

        while(sentence.length() > 0){

            if (sentence.indexOf(' ') == -1){
                pos = sentence.length();
                newSent = "";
            } else {
                pos = sentence.indexOf(' ');
                newSent = sentence.substring(pos+1);
            }
            word = sentence.substring(0,pos);

            sentence = newSent;

            if (word.length() >= minLength){
                wordCount++;
            }


            System.out.println("word = " + word);
            System.out.println("newSent = " + newSent);
            System.out.println("wordCount = " + wordCount);
        }
    }

Answer 1

对于没有更多空格的情况，您不会检查indexOf()的结果。

 pos = sentence.indexOf(' ');
 word = sentence.substring(0,pos);

当剩余字符串中没有更多空格时，对indexOf()的调用将返回-1。

然后对substring(0,-1)的后续调用将抛出IndexOutOfBoundsException，因为0＆gt; -1。

来自String.substring(int,int)的javadoc：

<强>抛出： IndexOutOfBoundsException - 如果beginIndex为负数，或者endIndex大于此String对象的长度，则或beginIndex大于endIndex 。

while（string.length＆gt; = 0）给出了StringIndexOutOfBoundsException错误

1 个答案: