java - 尝试扫描特定单词的 txt 文件时出现逻辑错误

Question

我有一个包含以下内容的 txt 文件：

Mary had a little lamb little lamb
little lamb. Mary had a little lamb.
That's all? Did the lamb follow Mary
wherever Mary went?

我正在尝试编写一些代码来扫描 txt 文件中的单词“Mary”，计算它出现的次数，然后打印该数字。

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

class Test {
    public static void main(String[] args) {
        int count = 0;

        Scanner reader = new Scanner("test.txt");

        while (reader.hasNextLine()) {
            String nextToken = reader.next();
            if (nextToken.equals("Mary"))
                count++;
        }

        System.out.println("The word 'Mary' was found on " + count + " lines.");
    }


}

代码编译时，我不断收到不正确的输入，系统打印"The word 'Mary' was found on 0 lines."

知道这里发生了什么吗？

Answer 1

您实际上并没有从文件中读取。

您需要将扫描仪声明为new Scanner(new File("test.txt"));否则，扫描仪实际上是在为 Mary 扫描字符串“test.txt”。

有关不同的构造函数，请参阅Scanner文档

Answer 2

vandale 是正确的，new Scanner("test.txt")应该是new Scanner(new File("test.txt"))。

但是，如果您想找出包含单词“Mary”的行数，则需要稍微更改您的代码。查看带有注释的行：

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

class Test {
    public static void main(String[] blargs) {
        int count = 0;

        Scanner reader = new Scanner(new File("test.txt"));

        while (reader.hasNextLine()) {
            String nextToken = reader.nextLine(); // nextLine() instead of next().
            if (nextToken.contains("Mary")) // contains() instead of equals()
                count++;
        }
        System.out.println("The word 'Mary' was found on " + count + " lines.");
    }
}