这是我运行StatsDemo时得到的错误。该程序不应该输出到控制台,但运行该程序将会在输出中创建一个名为Results.txt的文件。你应该得到的结果是:你应该得到77.444的平均值和10.021的标准偏差。即使我没有编译错误,我为什么在运行程序时遇到此错误?
运行StatsDemo。
这个程序计算含有一系列数字
的文件统计输入文件名:[DrJava输入框]
java.util.NoSuchElementException:没有找到行
在java中。 util.Scanner.nextLine(Scanner.java:1540)
在StatsDemo.main(StatsDemo.java:34) 在sun.reflect.NativeMethodAccessorImpl.invoke0(本机方法)
在sun.reflect.NativeMethodAccessorImpl.invok E(NativeMethodAccessorImpl.java:62)
在sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
在java.lang.reflect.Method.invoke(Method.java:498)
在edu.rice .cs.drjava.model.compiler.JavacCompiler.runCommand(JavacCompiler.java:272)
下面是代码:
import java.text.DecimalFormat; //for number formatting
import java.util.Scanner; //for keyboard input
import java.io.*; //for using files
public class StatsDemo
{
public static void main(String [] args)throws IOException {
double sum = 0; //the sum of the numbers
int count = 0; //the number of numbers added
double mean = 0; //the average of the numbers
double stdDev = 0; //the standard deviation of the numbers
String line; //a line from the file
double difference; //difference between the value and the mean
//create an object of type Decimal Format
DecimalFormat threeDecimals = new DecimalFormat("0.000");
//create an object of type Scanner
Scanner keyboard = new Scanner (System.in);
String filename; // the user input file name
//Prompt the user and read in the file name
System.out.println("This program calculates statistics"
+ " on a file containing a series of numbers");
System.out.print("Enter the file name: ");
filename = keyboard.nextLine();
//ADD LINES FOR TASK #4 HERE
File rf = new File("Numbers.txt");
Scanner inputFile = new Scanner(rf);
while (inputFile.hasNextDouble())
{
sum += inputFile.nextDouble();
count ++;
inputFile.nextLine();
}
inputFile.close();
mean = sum/count;
//ADD LINES FOR TASK #5 HERE
File rf2 = new File("Numbers.txt");
Scanner inputFile2 = new Scanner(rf2);
sum = 0;
count = 0;
//priming read to read the first line of the file
while (inputFile.hasNext())
{
difference = inputFile.nextDouble() - mean;
sum += Math.pow(difference,2);
count++;
if (inputFile.hasNextDouble())
inputFile.nextLine();
}
inputFile.close();
stdDev = Math.sqrt(sum/count);
//ADD LINES FOR TASK #3 HERE
FileWriter fwriter = new FileWriter("Numbers.txt", true);
PrintWriter outputFile = new PrintWriter(fwriter);
outputFile.print("mean = " + mean);
outputFile.print("deviation = " + stdDev);
outputFile.close();
System.out.println("Data written to file");
}
}
缺少编译器错误并不意味着程序没有bug,实际上你的程序不能处理你给它的输入。虽然我们无法帮助你,但没有代码。 –
因为你做错了什么。 –
因为这是运行时错误。你关了扫描仪,也许?没有线路被发现...很难说没有你的代码 –