FileInputStream 没有读取第一个值

Question

我需要读取的文件如下所示：

• 30 15
• 6 3
• 12 20
• 3 4

（不带项目符号）

inputStream 不是读取 30 和 15，而是读取所有其他的。

如何让 inputStream 读取第一行？

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

public class Program6 {
    //  private static Fraction [] fractionArray;
    public static void main(String[] args) throws FileNotFoundException, IOException {
        System.out.println("Please enter the name of the input file: ");


        Scanner inputFile = new Scanner(System.in);
        Scanner outputFile = new Scanner(System.in);

        String inputFileName = inputFile.nextLine();
        System.out.println("Please enter the name of the output file: ");
        String outputFileName = outputFile.nextLine();
        BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(System.out));
        FileWriter fileWriter = new FileWriter(outputFileName, true);
        //Declaring an inputstream to get file
        Scanner inputStream = new Scanner(new FileInputStream(inputFileName));


        //while the file still has a line
        while (inputStream.hasNextLine()) {
            String theLine = inputStream.nextLine();
            if (theLine.length() >= 0) {
                //declares a numerator and denominator from the file
                int num = inputStream.nextInt();
                int denom = inputStream.nextInt();
                //new fraction from file
                Fraction fract = new Fraction(num, denom);
                fract.reduce();
                System.out.println(fract);
                fileWriter.write("" + fract + "\r\n");
            }
        }

        //closes streams and flushes the file writer
        fileWriter.flush();
        fileWriter.close();
        inputStream.close();
    }
}

Answer 1

这里的问题是Scanner.nextLine() 消耗来自 InputStream 的输入行。然后，使用 Scanner.nextInt() 返回从同一个 InputStream 消费 - 它不会从 nextLine() 返回的值消费。

所以，使用一个或另一个。

如果使用nextLine() 方法，则需要解析包含该行的字符串以提取值。使用scanner.nextInt()，文件中的整数值立即可用。唯一的损失是您会失去对值是在同一行还是在不同行上的知识。