Question

The input file should be called 'data.txt' and should be created according to the highlighted instructions below. Note that even though you know the name of the input file, you should not hard-code this name into your program. Instead, prompt the user for the name of the input file.

The input file should contain (in order): the weight (a number greater than zero and less than or equal to 1), the number, n, of lowest numbers to drop, and the numbers to be averaged after dropping the lowest n values.

You should also prompt the user for the name of the output file, and then print your results to an output file with the name that the user specified.

• Your program should allow the user to re-enter the input file name if one or more of the exceptions in the catch clauses are caught.
• Your methods for getting data and printing results should each throw a FileNotFoundException which should be caught in the main method.
• Use try-with-resources statements (Links to an external site.) in your methods for getting and printing the data, and so avoid the need to explicitly close certain resources.
• In your readData method, use hasNextDouble to check ahead of time whether there's a double in the data. That way when you try to get the nextDouble, your code won't throw a NoSuchElementException.

You can use a writeFile method that does all the work (i.e., does not call a writeData method the way that Horstmann’s readFile method calls a readData method). Use a try-with-resources statement in your writeFile method when creating a new PrintWriter.

The inputValues come from a single line in a text file (data.txt) such as the following:
0.5 3 10 70 90 80 20

The output in the output file must give the weighted average, the data and weight that were used to calculate the weighted average, and the number of values dropped before the weighted average was calculated.

Your output should look very much like the following: "The weighted average of the numbers is 42.5, when using the data 10.0, 70.0, 90.0, 80.0, 20.0, where 0.5 is the weight used, and the average is computed after dropping the lowest 3 values."

Write the output to a file with the filename that the user chose to name the output file (e.g., output.txt). Don't hard-code the output file name in your program.

Creating the Input File

To create the input file, while in NetBeans with your project open, first click to highlight the top-level folder of your project, which should be called WeightedAvgDataAnalyzer.

Then from the File menu do this:

File->New File

Keep the Project name at the top; keep Filter blank

Categories choose Other (at the bottom of the categories list)
File Types choose Empty File (at the bottom of the files list)
Next->

FileName: data.txt
Folder: this should be blank; if it's not, delete whatever's there.
Finish

In the empty file data.txt that you just created, add a single line of data like that shown in the example above, where the weight is a double (greater than 0.0 and less than or equal to 1.0) and the other numbers are the number, n, of lowest values to drop and then the numbers to be averaged after dropping the lowest n values.

Code In Java

Answer 1

import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileWriter;
import java.io.PrintWriter;
import java.util.Arrays;
import java.util.LinkedList;
import java.util.Scanner;
public class WeightedAvgDataAnalyzer {
public static LinkedList<LinkedList<Double>> inputDataList = new LinkedList<LinkedList<Double>>();//LinkedList to store input data
public static LinkedList<String> outputDataList = new LinkedList<String>();//LinkedList to store calculated data
public static void main(String[] args) {
Scanner userInput = null;// User Input Scanner
try {
userInput = new Scanner(System.in);// User Input Scanner
//Iterating infinite loop till user enters correct input file
while (true) {
System.out.println("Pleasee Enter Input File Name:");
String inFileName = userInput.next(); //Getting Input File Name from user
File file = new File(inFileName); //Creating File object using Input File Name
//Checking weather file is exists or not
if (file.exists()) {
readData (inFileName); //Reading data from input text file and creating data list
break;//terminating infinite loop
} else {
throw new FileNotFoundException("File not Found!");
}
}
System.out.println("Pleasee Enter Output File Name:");
String outFileName = userInput.next(); //Getting Out File Name from user
calculateWeightedAvg(); //Calculating Average Weighted Value of input data
writeFile (outFileName);//Writing Average Weighted Value to output file
} catch (Exception e) {
e.printStackTrace();
} finally {
try {
if (userInput != null) {
userInput.close();//closing scanner
}
} catch (Exception e) {
e.printStackTrace();
}
}
}
// This method is to read input file
public static void readData(String fileName) {
//try-with-resources statement to read input file
try (Scanner scanner = new Scanner(new File(fileName))) {
//Iterating scanner for each line of input text file
while (scanner.hasNextDouble()) {
String line = scanner.nextLine();// getting new line from text file
String[] lineArray = line.trim().split("\\s+");// Splitting each line by space to get string array
LinkedList<Double> subDataList = new LinkedList<Double>();//Creating sublist for each line of input text file
subDataList.add(Double.parseDouble(lineArray[0])); //Adding weight into list
subDataList.add(Double.parseDouble(lineArray[1])); //Adding dropping value
//Iterating loop to get Data from line
for (int i=2;i<lineArray.length;i++) {
subDataList.add(Double.parseDouble(lineArray[i])); //Adding rest of the data
}
inputDataList.add(subDataList);//adding sub list into actual list
}
} catch (Exception e) {
e.printStackTrace();
}
}
// This method will calculate weighted average data and storing it to output list
public static void calculateWeightedAvg () {
try {
//Checking weather input list is not empty
if (inputDataList != null && inputDataList.size()>0) {
//Iterating input list
for (int i=0;i<inputDataList.size();i++) {
LinkedList<Double> subDataList = inputDataList.get(i);//Getting each sublist
//Checking weather sublist is not empty
if (subDataList != null && subDataList.size()>0) {
String outputMsg1 = "The weighted average of the numbers is ";//Creating output message
String outputMsg2 = " when using the data ";//Creating output message
Double weight = subDataList.get(0);//Getting weight
Double dropingValue = subDataList.get(1);//Getting dropping value
Double[] dataArry = new Double[subDataList.size()-2];//Creating Data Array
int dataCount = 0;//Declaring data count as zero
//iterating loop to get data and adding them into double array
for (int j=2;j<subDataList.size();j++) {
outputMsg2 = outputMsg2 + subDataList.get(j) +", ";//Creating output message
dataArry[dataCount] = subDataList.get(j);//adding data in array
dataCount++;//increasing data count by 1
}
outputMsg2 = outputMsg2+"where "+weight+ " is the weight used, and the average " +
"is computed after dropping the lowest "+dropingValue+" values.";//Creating output message
Arrays.sort(dataArry);//Sorting data array
double totalWeightedValue = 0;//Declaring total Weighted Value
dataCount = 0;//setting data count as zero again for below use
//Below loop will iterate till dropping values reached in the array
for (double k=(int)dataArry.length-1;k>=dropingValue;k--) {
double data = dataArry[(int) k]; //getting data
double weightedValue = data*weight; //calculating weighted value
totalWeightedValue = totalWeightedValue + weightedValue; //adding weighted value to total weighted value
dataCount++; //data count increase by 1
}
double totalWeightedAvg = totalWeightedValue/dataCount;//calculating average weighted value
outputDataList.add(outputMsg1+totalWeightedAvg+outputMsg2); //finally appending all the output message and adding it to output list
}
}
}
} catch (Exception e) {
e.printStackTrace();
}
}
// This method is to write to output file
public static void writeFile(String fileName) {
//Checking weather output list is not empty
if (outputDataList != null && outputDataList.size()>0) {
//try-with-resources statement to write in output file
try (PrintWriter pw = new PrintWriter(new FileWriter(fileName))) {
//iterating output list to get output data
for (int i=0;i<outputDataList.size();i++) {
pw.println(outputDataList.get(i));//writting output data into output file
}
} catch (Exception ioe) {
ioe.printStackTrace();
}
System.out.println("Output File Created!");
}
}
}

OUTPUT:

Console X <terminated> WeightedAvgData Analyzer (Java Application CA Program FilesVavajre7bir Pleasee Enter Input File Name: data.txt Pleasee Enter Output File Name: output.txt putput File Created!

data.txt - Notepad File Edit Format View Help 0.5 3 10 70 90 80 20 output.txt - Notepad File Edit Format View Help The weighted average of the numbers is 42.5 when using the data 10.0, 70.0, 90.0, 80., 20.0, where 0.5 is the weight used, and the average is computed after dropping the lowest 3.0 values.