Question

我在这里有一个.txt文件“C：\ failass.txt”。它包含以下信息：

AA051245445454552117989
LT647044001231465456
LT517044077788877777
LT227044077788877777
CC051245445454552117989

我找到了一个代码，用于扫描用户输入是否与文件中包含的信息匹配：

package ibanas;

import java.util.Scanner;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.util.Scanner;

public class ReadFromFile {

public static void main(String[] args) throws IOException {
    Scanner myScanner = new Scanner(System.in);
    System.out.println("What number would you like to check for?");
    String number = myScanner.nextLine();
    if(isFound(number)){
        System.out.println("The number "+number+ " is there");
    }else{
        System.out.println("The number "+number+ " doesn't exist");
    }
}

public static boolean isFound(String number) {

    Scanner sc = new   Scanner(ReadFromFile.class.getResourceAsStream("C:\failass.txt"));
    String word="";
    while (sc.hasNextLine()) {
        word = sc.next();

        if (word.equals(number.trim())) { 
            return true;
        }
    }
    return false;
}
}

但是当我输入（例如）此行AA051245445454552117989时，它会给我以下错误：

What number would you like to check for?
AA051245445454552117989
Exception in thread "main" java.lang.NullPointerException
at java.io.Reader.<init>(Unknown Source)
at java.io.InputStreamReader.<init>(Unknown Source)
at java.util.Scanner.<init>(Unknown Source)
at ibanas.ReadFromFile.isFound(ReadFromFile.java:24)
at ibanas.ReadFromFile.main(ReadFromFile.java:15)

感谢您的任何建议：）

Answer 1

扫描程序的arg，即ReadFromFile.class.getResourceAsStream("C:\failass.txt")返回null。可能是因为你需要用另一个"C:\\failass.txt"

来逃避反斜杠

检查文件是否包含用户输入的数字（java）

1 个答案: