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CSE142 Program Example handout #18
Input file numbers.txt
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85 93.2 97.5 18.5 394.23
-18 45.2 19.8 47.3
42
8 8 8 8 32
2.4 -2.4 3.5 -500
Log of execution
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This program processes an input file of numbers.
What is the name of the input file? foo.txt
File not found. Please try again.
What is the name of the input file? numbers.dat
File not found. Please try again.
What is the name of the input file? numbers.txt
Total numbers = 5
average = 137.686
minimum = 18.5
maximum = 394.23
Total numbers = 4
average = 23.575
minimum = -18.0
maximum = 47.3
Total numbers = 1
average = 42.0
minimum = 42.0
maximum = 42.0
Total numbers = 5
average = 12.8
minimum = 8.0
maximum = 32.0
Total numbers = 4
average = -124.125
minimum = -500.0
maximum = 3.5
Program file Numbers.java
-------------------------
// Stuart Reges
// 11/8/04
//
// This program processes an input file of numbers, reporting for each line of
// input the number of numbers and their average, minimum and maximum.
import java.io.*;
public class Numbers {
public static void main(String[] args) {
System.out.println("This program processes an input file of numbers.");
System.out.println();
Scanner console = new Scanner(System.in);
Scanner input = getInput(console);
process(input);
}
// prompts the user for a file name and reads the result using the
// console Scanner until the user gives a legal file name
public static Scanner getInput(Scanner console) {
Scanner result = null;
while (result == null) {
System.out.print("What is the name of the input file? ");
String name = console.nextLine();
try {
result = new Scanner(new File(name));
} catch (FileNotFoundException e) {
System.out.println("File not found. Please try again.");
}
}
System.out.println();
return result;
}
// processes an entire input file line by line
public static void process(Scanner input) {
while (input.hasNextLine()) {
String text = input.nextLine();
Scanner data = new Scanner(text);
processLine(data);
}
}
// processes a series of numbers from the given Scanner, reporting
// the number of numbers along with the average, minimum and maximum
// of the numbers; assumes that at least one number can be read
public static void processLine(Scanner data) {
// read first number outside the loop to initialize min/max
double next = data.nextDouble();
double sum = next;
double min = next;
double max = next;
int count = 1;
while (data.hasNextDouble()) {
next = data.nextDouble();
sum += next;
count++;
if (next < min)
min = next;
if (next > max)
max = next;
}
reportResults(count, sum/count, min, max);
}
// reports the overall statistics for a group of numbers
public static void reportResults(int count, double average,
double min, double max) {
System.out.println("Total numbers = " + count);
System.out.println("average = " + average);
System.out.println("minimum = " + min);
System.out.println("maximum = " + max);
System.out.println();
}
}
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