Scanner.hasNext()导致无限循环 [英] scanner.hasNext() results in an infinite loop

问题描述

我有一段代码，应该逐字读取输入的内容，并将该单词的长度递归地添加到ArrayList中(用于学校练习).

I have a piece of code which should read input word by word and add the length of the word to an ArrayList recursively (for a school exercise).

我写了这个方法:

ArrayList<Integer> wordLengths = new ArrayList<Integer>();
Scanner scanner = new Scanner(System.in);
// ...
private void readWords() {
    // read a word, if there are more words, read the next word
    this.wordLengths.add(this.scanner.next().length());

    if (this.scanner.hasNext()) {
        readWords();
    }
}

当我调用此方法时，它会不断询问新单词.它不会停止(递归)循环.为什么会这样呢? this.scanner.hasNext()仅在输入中有下一个单词时才为true，因此在没有其他单词时应停止.

When I call this method, it keeps asking for new words. It won't stop the (recursive) loop. Why is this happening? this.scanner.hasNext() should only be true when there's a next word in the input so it should stop when there is no other word.

推荐答案

System.in 是输入流.它永远不会关闭，因此对于#hasNext()

System.in is an input stream. It is never closed, so it will always return true for #hasNext()

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