Question

I have to make a marks program that displays a set of marks that a user enters and some calculations (average, maximum, minimum, range, etc.). It should also be able to sort the marks in ascending order. I managed (with help) to display the marks and sort them but I cannot get the program to do the calculations and display them. This is all the code I have so far:

 ArrayList <Integer> marks = new ArrayList();

 private void addButtonActionPerformed(java.awt.event.ActionEvent evt) {
    Collections.addAll(marks, (Integer.parseInt(markInput.getText())));

    StringBuilder text = new StringBuilder();
    for (Integer mark: marks) {
    text.append(mark.toString()).append('\n');
    }

    markdisplayTextArea.setText(text.toString());
    }

 private void sortButtonActionPerformed(java.awt.event.ActionEvent evt) {
    Collections.sort(marks);

    StringBuilder text = new StringBuilder();
    for (Integer mark: marks) {
    text.append(mark.toString()).append('\n');
    }

    markdisplayTextArea.setText(text.toString());
    }

 private void analyzeButtonActionPerformed(java.awt.event.ActionEvent evt) {

    analyzeTextArea.setText("Class average:" +);
    analyzeTextArea.setText("Maximum mark:" +);
    analyzeTextArea.setText("Minimum mark:" +);
    analyzeTextArea.setText("Range of marks:" +);
    }

The calculations must be displayed in a TextArea when the "analyze" button is pressed. I currently have no idea of how to go about doing the calculations or displaying them. Any guidance would be appreciated.

Answer 1

Here is my suggested code for your problem…

ArrayList<Integer> marks = new ArrayList<Integer>();

// Called when the user clicks a button
public void actionPerformed(ActionEvent e) {
    Object clickedButton = e.getSource();
    if(clickedButton == addButton) {
        addButtonActionPerformed();
    }
    else if(clickedButton == sortButton) {
        sortButtonActionPerformed();
    }
    else if(clickedButton == analyzeButton) {
        analyzeButtonActionPerformed();
    }
}

 private void addButtonActionPerformed() {
    Collections.addAll(marks, (Integer.parseInt(markInput.getText())));

    StringBuilder text = new StringBuilder();
    for (Integer mark: marks) {
        text.append(mark.toString()).append('\n');
    }

    markdisplayTextArea.setText(text.toString());
}

 private void sortButtonActionPerformed() {
    Collections.sort(marks);

    StringBuilder text = new StringBuilder();
    for (Integer mark: marks) {
        text.append(mark.toString()).append('\n');
    }

    markdisplayTextArea.setText(text.toString());
}

private void analyzeButtonActionPerformed() {

    String output = "Class average:" + calculateAverage() + "\n" +
                    "Maximum mark:" + calculateMaximum() + "\n" +
                    "Minimum mark:" + calcualteMinimum() + "\n" +
                    "Range of marks:" + calculateRange();

    analyzeTextArea.setText(output);
}

private int calculateAverage(){
    // calculate and return the answer
}

private int calculateMaximum(){
    // calculate and return the answer
    int maximum = 0;
    for (Integer currentMark: marks){
        if (currentMark > maximum){
            maximum = currentMark;
        }
    }
    return maximum;
}

private int calcualteMinimum(){
    // calculate and return the answer
}

private int calculateRange(){
    // calculate and return the answer
}

Now, these are my main changes, and why I made them…

1. I added a actionPerformed() method. If you don’t have this already, it allows you to listen for button clicks. You need to add a line myButton.addActionListener(this); for each of your buttons. You’ll probably also need to change your public class MyClass line to say public class MyClass implements ActionListener, and add a line import java.awt.event.*
2. I changed your analyzeButtonActionPerformed() method so that it outputs the values you requested. Now you need to implement the calculate() methods at the end – I have done one of them for you to give you the general idea. When you click the analyze button, it should do all the 4 calculations and put the answers in the textarea.

Why don’t you have a bit of a look at my changes, and see whether you can see what they’re supposed to be doing. Have a go at implementing some of the changes, and the calculate methods, and see if you can get it working. Don’t just copy-paste my answer – make some changes bit-by-bit to see how it all works, and fix any compilation errors as they appear.