Question

我正在创建一个程序，它将文件名作为参数并检查文本中的回文。该程序还将根据用户输入替换字母或根据用户输入删除单词。出于某种原因，

下的扫描仪

public void letter

and 

public void word

无法正常工作。

这是程序运行后我收到的错误，用户输入：

What would you like to do? Here are your options: 

Press 1 to Print all palindromes 

Press 2 to Replace any letter  

Press 3 to remove all occurences of a word 

Press 4 to exit

2

What letter would you like to remove?

e

What letter would you like to add?

r

[ ]

What would you like to do? Here are your options: 

Press 1 to Print all palindromes 

Press 2 to Replace any letter  

Press 3 to remove all occurences of a word 

Press 4 to exit

这是我得到的错误

Exception in thread "main" java.util.NoSuchElementException
at java.util.Scanner.throwFor(Scanner.java:907)
at java.util.Scanner.next(Scanner.java:1416)
at Homework6.main(Homework6.java:28)**

代码：

import java.util.ArrayList;
import java.util.Scanner;
import java.util.*;
import java.io.File;

public class Test {

static ArrayList<String> strings = new ArrayList<String>();

public static void main(String[] args) {
    Test test2 = new Test();
    try {
        Scanner scanner = new Scanner(new File(args[0]));
        while (scanner.hasNext()) {
            strings.add(scanner.next());
        }
    } catch (Exception e) {
    }

            //ArrayList<String> a = new ArrayList<String>(strings);
    while (true) {
        System.out.println("\nWhat would you like to do? Here are your options: \nPress 1 to Print all palindromes \nPress 2 to Replace any letter  \nPress 3 to remove all occurences of a word \nPress 4 to exit\n");
        Scanner s = new Scanner(System.in);
        String command = s.next();

        if (command.equals("1")) {
            test2.pal();
        } else if (command.equals("2")) {
            test2.letter();
        } else if (command.equals("3")) {
            test2.word();
        } else if (command.equals("4")) {
            System.exit(0);
        }
    }
}

public void pal() {
    int a;
    int c;
    // boolean isPalindrome() ;

    for (a = 0; a < strings.size(); a++) {
        String replace = strings.get(a);
        replace = replace.replaceAll("[.,']", "");
    }

    for (c = 0; c < strings.size(); c++) {
        boolean pal = PalindromeChecker.isPalindrome(strings.get(c));

        if (true) {
            System.out.print(strings.get(c));
        }
    }
}

public void letter() {

    int b;
    Scanner replaceLetter = new Scanner(System.in);
    System.out.println("What letter would you like to remove?");
    String badLetter = replaceLetter.next();
    System.out.println("What letter would you like to add?");
    String newLetter = replaceLetter.next();
    for (b = 0; b < strings.size(); b++) {
        String replaceVowels = strings.get(b);
        replaceVowels = replaceVowels.replace("badVowel", "newVowel");
    }
    replaceLetter.close();

    System.out.print(strings);
}

public void word() {

    Scanner removeWord = new Scanner(System.in);
    System.out.println("What word would you like to remove?");
    String word = removeWord.next();
    strings.remove(word);
    removeWord.close();
    System.out.print(strings);
}
}

Answer 1

删除这些行..它会起作用......

     replaceLetter.close ();
     removeWord.close();

Answer 2

扩展@TheLostMind的答案，问题是当你调用Scanner#close时，如果它实现Closeable接口，它也将关闭底层流。取自文档：

如果此扫描仪尚未关闭，则表明其底层可执行也实现了Closeable接口，然后可读将调用close方法。如果此扫描仪已经关闭，那么调用此方法将无效。

因此，在您的letter()和word()函数中，当您调用close时，它也将关闭System.in 。因此，当您尝试使用Scanner再次从System.in读取时，没有什么可以阅读，而您获得了NoSuchElementException。

Answer 3

使用

while(scanner.hasNextLine()){}

和scanner.nextLine

代替hasNext()＆amp; next()。

如果您使用java7，那么最好像这样编码：

try (Scanner scanner = new Scanner(new FileInputStream(file)) {

}

它会自动关闭Scanner并且对任何类型的leak

都是安全的

扫描程序错误与数组列表

3 个答案: