Finding highest of 10

Question

I'm gonna be honest, I've been working on an assignment and I am BEYOND stuck. I'm creating a simple java applet that lets the user input 10 numbers. the program sanitizes that input, making sure only a number is entered, and that the number must be between 0 and 9.

so far no problems. used given examples, searched the web for proper syntax and logic. my code compiles without complaining. however once i try my first number, as long as its valid input, my program just ups and tells me the number i just entered is the largest, and doesn't wait for to enter 10 numbers.

My guess is that i have half an applet program, and I'm not outputting right, or something in my loop is wrong, but the logic seems good.

almost forgot to mention. i don't know how to make output text in the applet, any help with that would be awesome, but its not my primary concern.

my current code:

import java.awt.*;
import java.applet.*;
import java.awt.event.*;
import javax.swing.JOptionPane;

public class largest extends Applet implements ActionListener{
private static final long serialVersionUID = 1L;


//Create components for Applet
Label numberLabel = new Label("Enter a number:");
TextField numberField = new TextField(10);  // Sets the size of the text field, You still may type as much data into the field that you want, input will need to be sanitized later

Label topNumberLabel = new Label("The top number is:");
Button calcButton = new Button("Ok");
public void init()
{
    // Add controls to the applet window
    add(numberLabel);
    add(numberField);
    add(topNumberLabel);
    add(calcButton);
    calcButton.addActionListener(this);
    setSize(300, 200);  // Sets the size of the applet window
}

public void actionPerformed(ActionEvent e) {
    // Variables for counting, user input, and storage for largest number
    double counter = 0;
    double number = 0;
    double largest = 0;

    // Allows user to input 10 times
    while (counter<10)
    {
        try { //Sanitize user input, make sure input entered is a number
            number = Double.parseDouble(numberField.getText());
        } catch (NumberFormatException ex) {
            numberField.requestFocus();
            JOptionPane.showMessageDialog(null, "Input invalid, please enter an integer",
                    "///-D-A-T-A---E-R-R-O-R-\\\\\\", JOptionPane.ERROR_MESSAGE);
            return;
        }
        if (number < 0 || number > 9) { //Sanitize user input, make sure the given number is between 0 and 9
            numberField.requestFocus();
            JOptionPane.showMessageDialog(null,
                    "The number entered must be between 0 and 9",
                    "///-D-A-T-A---E-R-R-O-R-\\\\\\", JOptionPane.ERROR_MESSAGE);
            return;
        }
        counter++;

    // Determine what the largest number entered is by comparing to a baseline
    // of previous numbers or zero if just beginning loop
    if (number > largest)largest=number;

    }

        // Display's the largest number that got entered by user
        JOptionPane.showMessageDialog(null," The largest number entered was " + largest);
    }

}

Answer 1

You are looping the 10 times as expected, but each time you are just getting the field's value with getText(). This doesn't wait for the user to change the number, so all 10 of the numbers are the same. You must define counter and largest as fields, and change each time actionPerformed is called. Here's code:

import java.awt.*;
import java.applet.*;
import java.awt.event.*;
import javax.swing.JOptionPane;

public class largest extends Applet implements ActionListener{
    private static final long serialVersionUID = 1L;

    private int counter = 0; // These are the variables
    private double largest = 0; // from actionPerformed().

    // ...

    public void actionPerformed(ActionEvent e) {
        // Variable for user input
        double number = 0;

        try { //Sanitize user input, make sure input entered is a number
            number = Double.parseDouble(numberField.getText());
        } catch (NumberFormatException ex) {
            numberField.requestFocus();
            JOptionPane.showMessageDialog(null,
                    "Input invalid, please enter an integer",
                    "///-D-A-T-A---E-R-R-O-R-\\\\\\",
                    JOptionPane.ERROR_MESSAGE);
            return;
        }
        if (number < 0 || number > 9) { //Sanitize user input, make sure the given number is between 0 and 9
            numberField.requestFocus();
            JOptionPane.showMessageDialog(null,
                    "The number entered must be between 0 and 9",
                    "///-D-A-T-A---E-R-R-O-R-\\\\\\",
                    JOptionPane.ERROR_MESSAGE);
            return;
        }
        counter++;
        // Determine what the largest number entered is by comparing to a baseline
        // of previous numbers or zero if just beginning loop
        if (number > largest)largest=number;
        // Allows user to input 10 times
        if (counter==10)
        {
            // Display's the largest number that got entered by user
            JOptionPane.showMessageDialog(null,
                    "The largest number entered was " + largest);
        }
    }
}

Answer 2

It is because this line

number = Double.parseDouble(numberField.getText());

is done 10 times as soon as you've entered a number in the field, you wouldn't get the time to change the number in the field before the loop is finished.