Question

Java program

Create a public method named saveData for a class named Signal that will hold digitized acceleration data. Signal has the following field declarations

private

    double timeStep;               // time between each data point

    int numberOfPoints;          // number of data samples in array

    double [] acceleration = new double [1000];          // acceleration data

    double [] velocity = new double [1000];        // calculated velocity data

    double [] displacement = new double [1000];        // calculated disp data

saveData will output a new file containing all of the data in the class. It will have a single String parameter that is the name of the file to be created. That file should have the timeStep on the first line, followed by the acceleration, velocity, and displacement data with all three values for the same index in the array on one line. There should be a comma and a single space separating the acceleration value from the velocity value, and the same between the velocity value and the displacement value. The number of data samples to be output is less than 1000 and is contained in numberOfPoints.

The method should create and open the file, put the timeStep into the file on the first line followed by the information from the arrays. At the end of the method close the file. In the method, be sure to catch an IOException error if there are any problems with the name of the file to be opened.

Answer 1

Program Code [JAVA]

// Signal class

import java.io.File;
import java.io.FileNotFoundException;
import java.io.PrintWriter;

class Signal {

    // Field Declarations

    private double timeStep;
    private int numberOfPoints;
    double[] acceleration = new double[1000];
    double[] velocity = new double[1000];
    double[] displacement = new double[1000];

    // Constructor which initializes number of points to 0

    public Signal() {
        numberOfPoints = 0;
    }

    // saveData method

    public void saveData(String fileName) {

        // Opening file & writing using PrintWriter

        try {
            PrintWriter writer = new PrintWriter(new File(fileName));

            // First writing timeStep on first line

            writer.write(timeStep + "\n");

            // Now writing acceleration, velocity and displacement data of same index in array

            for (int i=0; i<numberOfPoints; i++) {

                writer.write(acceleration[i] + ", " + velocity[i] + ", " + displacement[i] + "\n");
            }

            writer.close();

        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }

    }

    // Some additional method to see that saveData is working good

    public void setNumberOfPoints(int numberOfPoints) {
        this.numberOfPoints = numberOfPoints;
    }

    public void setTimeStep(double timeStep) {
        this.timeStep = timeStep;
    }

    public void setData(double acc, double velocity, double displacement) {

        this.acceleration[numberOfPoints] = acc;
        this.velocity[numberOfPoints] = velocity;
        this.displacement[numberOfPoints] = displacement;

        numberOfPoints++;   // For next entry
    }
}

// A class to test method saveData in Signal class

public class TestSignal {

    public static void main(String[] args) {

        // adding some data and then storing in file

        Signal signal = new Signal();

        signal.setTimeStep(3);
        signal.setData(10.1, 5.7, 3.4);
        signal.setData(5.6, 3.25, 5.8);
        signal.setData(8.9, 2.0, 1.3);

        signal.saveData("output.txt");
    }
}

output.txt

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