正确读取文件输入的问题

Question

在我当前的项目中，我必须从输入文件中读取一些数字（第一个是系数，第二个是其中的指数）。出于某种原因，我在使用“Integer.parseInt”时遇到错误。有谁知道 why/how 来解决这个问题？当前代码如下。

错误信息：

Exception in thread "main" java.lang.NumberFormatException: For input string: "2 5 "
    at java.base/java.lang.NumberFormatException.forInputString(NumberFormatException.java:68)
    at java.base/java.lang.Integer.parseInt(Integer.java:652)
    at java.base/java.lang.Integer.parseInt(Integer.java:770)
    at polynomialproject.Driver.main(Driver.java:35)


Java returned: 1
BUILD FAILED (total time: 0 seconds)

输入文件：

Driver:

import java.io.*; //Can use all io's
import java.util.*; //Can use all util's
import polynomialproject.SortedLinkedList;
import polynomialproject.SortedListInterface;

public class Driver {
    
    private static Scanner file;
    static PrintWriter outputFilePrinter;
    static Scanner inputFileScanner;

    public static void main(String[] args) throws FileNotFoundException {
        
        Scanner inFile;
        PrintWriter printWriter = new PrintWriter("output.txt");  //printWriter will output to proper text
        inFile = new Scanner(new File("input.txt"));
        
        Polynomial One = new Polynomial();
        
         while (inFile.hasNext()) {
                String String1 = inFile.nextLine(); //Reads lines
                int one = Integer.parseInt(String1);
                String String2 = inFile.nextLine();
                int two = Integer.parseInt(String2);
                One.setTerm(two, one);
         }
         
        Polynomial Two = new Polynomial();
         
        while (inFile.hasNext()){
            String String1 = inFile.nextLine();
            int one = Integer.parseInt(String1);
                String String2 = inFile.nextLine();
                int two = Integer.parseInt(String2);
                One.setTerm(two, one);
        
        }
        
        printWriter.println(One.toString());
        printWriter.println("The degree of the first polynomial is: " + One.getDegree());
        printWriter.println("The coefficient of exponent two is: " + One.getCoefficient(2));
        printWriter.println("The coefficient of exponent three is: " + One.getCoefficient(3));
        
        printWriter.println("The degree of the second polynomial is: " + Two.getDegree());
        printWriter.println("The sum of the polynomials is: " + Two.sum(Two));
        
        printWriter.close();
    }//End main
    
}//End Driver

Answer 1

nextLine() 读取一行文本。这就是为什么它有那个名字。

您不需要 1 行文字；毕竟，1 行包含 2 个整数。你只想要一个整数。

调用 .nextInt()（忘记 Integer.parseInt）。

Answer 2

您在一个 while 循环中跳过了 2 行，请不要那样做。由于您一次扫描整行，因此还需要在阅读后拆分该行（使用 space 作为 delim）。

while (inFile.hasNext()) {
        String line = inFile.nextLine();
        String[] numbers = line.split(" ");
        int one = Integer.parseInt(numbers[0]);
        int two = Integer.parseInt(numbers[1]);
        One.setTerm(two, one);
}

此外，扫描器就像迭代器一样 - 一旦您在 while 循环中使用它，它就被“使用”了。要再次扫描文件，您需要在两个 while 循环之间再次创建它：

inFile = new Scanner(new File("input.txt"));

正确读取文件输入的问题

Problem with reading input from file properly

java

netbeans