Question

这应该隔离名称和分数，然后计算分数的平均值。输出应如下所示：

Student Name             Test 1    Test 2    Test 3     Final   Average 

Susan Smith                 76        78        90       100     88.80

Susan Boyd                 100        88        79        88     88.60

Alex Chandler               88        99        77        66     79.20

但它不断抛出stringindexoutofboundsexception。为什么呢？

这是错误：

java.lang.StringIndexOutOfBoundsException: String index out of range: 0
at java.lang.String.charAt(String.java:646)
at CalcWeightedAverage.extractName(CalcWeightedAverage.java:49)
at CalcWeightedAverage.main(CalcWeightedAverage.java:30)

以下是代码：

import java.util.*; //import java.util for the scanner
import java.io.*;// import java io for printwriter

/**
 * class takes input file with scores and outputs scores with weighted average
 *
 * @author
 * @version 10/30/2015
 */
public class CalcWeightedAverage {
    /**
     * method akes input file with scores and outputs scores with weighted average
     *
     * @param String args
     * @return void
     */
    public static void main(String[] args) throws FileNotFoundException {
        Scanner in = new Scanner(System.in); // creating scanner to read from the keyboard
        System.out.print("Please enter the name of the input file: "); // prompt for file name
        PrintWriter out = new PrintWriter("OutputFile.txt"); // declares new printwriter for outputfile name
        String filename = in.nextLine(); // puts user input as filename
        File inFile = new File(filename);//makes a new file and puts user input in it 
        Scanner in1 = new Scanner(inFile);// declaring scanner for whats in file
        out.printf("%-21s%10s%10s%10s%10s%10s", "StudentName", "Test 1", "Test2", "Test 3", "Final", "Average"); // first line in output
        out.println(); // go to next line
        while (in1.hasNextLine()) {
            String line = in1.nextLine(); // new string from file
            String studentName = extractName(line); // extracts the student name using the method
            double[] studentscore = new double[5]; // new array to store values
            studentscore = extractValue(line);// invoke method to calculate values
            out.printf("%-20s%10.0f%10.0f%10.0f%10.0f%10.2f", studentName, studentscore[0], studentscore[1], studentscore[2], studentscore[3], studentscore[4]); // edit scores
            out.println();// next line
        }
        in.close(); // closes scanner
        in1.close();//closes scanner
        out.close();//closes printwriter
    }


    /**
     * Extracts the student name from an input line.
     *
     * @param pline a line containing a student name, followed by a number
     * @return the student name
     */
    public static String extractName(String pline) {
        int i = 0; // Locate the start of the first digit
        while (!(Character.isDigit(pline.charAt(i)))) {
            i++;
        }
        return pline.substring(0, i).trim(); // Extract the student name and return
    }

    /**
     * Extracts the value from an input line.
     *
     * @param pline a line containing a student name, followed by a value
     * @return the value associated with the name
     */
    public static double[] extractValue(String pline) {
        int i = 0; // Locate the start of the first digit
        while (!Character.isDigit(pline.charAt(i))) {
            i++;
        }
        // Extract and convert the value
        String scoreString = pline.substring(i).trim(); // extract score and return
        Scanner score = new Scanner(scoreString); // new scanner for score
        int testScore1 = score.nextInt(); // value of first score
        int testScore2 = score.nextInt();// value of second score
        int testScore3 = score.nextInt();// value of third score
        int finalscore = score.nextInt();// value of final score
        double average = testScore1 * 0.2 + testScore2 * 0.2 + testScore3 * 0.2 + finalscore * 0.4; // calculates the weighted average
        double[] result = new double[5];// new array for input
        result[0] = testScore1;// value of first score
        result[1] = testScore2;// value of second score
        result[2] = testScore3;// value of third score
        result[3] = finalscore;//value of final score
        result[4] = average; // value of average
        return result;// return average
    }
}

Answer 1

问题出在输入文件中，它必须有很少的空格，否则它不起作用

Java，我不断收到StringIndexOutOfboundsException

1 个答案: