Apple Developer Connection Student Program/ADC Tools Sampler CD Disk 3 1999.iso/Documentation/Books/Learn Java on the Macintosh/Learn Java Projects/12.04 - Payroll/Payroll.java

Text File | 1996-04-22 | 5KB | 185 lines

/* -----------------------------------------------------------
   This illustrates a few standard classes and basic applet behavior.
   Enter an employee number for an employee into a text field.
   If this employee exists, the applet will find the employee and
   display the employee's payroll information. Otherwise, the applet
   will create a new employee and add the employee to the database.

   Java's classes: Applet     (applet)
                   TextField  (awt)     to enter new employee data
                   Label      (awt)     read-only text
                   GridLayout (awt)     aligns by columns and rows
                   Event      (awt)     user-generated action
                   Hashtable  (util)    database
                   String     (lang)    text
                   Integer    (lang)    number

   Custom classes: Payroll
                   Employee             payroll information

----------------------------------------------------------- */
import java.applet.Applet;
import java.awt.*;
import java.util.*;

public class Payroll extends Applet {
    Hashtable  db;
    TextField  textFieldEmployee;
    TextField  textFieldWage;
    TextField  textFieldHours;
    Label      labelEarned;
    Employee   current;

    /* Create user interface needed by this applet. */
    public void init() {

        // Create the employee database.
        db = new Hashtable();

        // Arrange the user interface in a grid.
        setLayout(new GridLayout(4,2)); // 4 rows, 2 columns

        // 1st row.
        add(new Label("Employee number:"));
        textFieldEmployee = new TextField(20); // 20 columns wide
        add(textFieldEmployee);

        // 2nd row.
        add(new Label("Hourly wage:"));
        textFieldWage = new TextField(20); // 20 columns wide
        add(textFieldWage);

        // 3rd row.
        add(new Label("Hours worked:"));
        textFieldHours = new TextField(20); // 20 columns wide
        add(textFieldHours);

        // 4th row.
        add(new Label("Earned income:"));
        labelEarned = new Label();
        add(labelEarned);

        setCurrent(null);
    }


    /** Handle events that propogate to the applet. This will include new text field data. */
    public boolean action(Event e, Object arg) {
        Employee employee;
        int         number;

        // Create/retrieve the employee according to the number the user entered.
        if (e.target == textFieldEmployee) {

            number = intFromTextField(textFieldEmployee);
            employee = findEmployee(number);

            // Create a new employee if the employee is not already there.
            if (employee == null)
                employee = addNew(number);

            // Display this employee's payroll information.
            setCurrent(employee);

        // Set the hourly wage for the current employee.
        } else if (e.target == textFieldWage) {

            if (current != null) {
                current.hourlyWage = intFromTextField(textFieldWage);
                recalcEarned();
            }

        // Set the number of hours worked for the current employee.
        } else if (e.target == textFieldHours) {

            if (current != null) {
                current.hoursWorked = intFromTextField(textFieldHours);
                recalcEarned();
            }
        }

        return super.action(e, arg);
    }

    /** This is a utility routine to retrieve an integer from a text field. */
    int intFromTextField(TextField tf) {
        String  s;
        int     value;

        s = tf.getText();
        try {
           value = Integer.parseInt(s);
        } catch (Exception e) {
           value = 0;
           setCurrent(null);
        }

        return value;
    }

    /** Do a database lookup using the employee's number as the key. */
    Employee findEmployee(int number) {
        return (Employee)db.get(new Integer(number));
    }

    /** Set the text fields to display the correct information for the current employee. */
    void setCurrent(Employee e) {
        current = e;

        // If there isn't a current employee, initialize the fields to 0.
        if (e == null) {
           textFieldEmployee.setText("0");
           textFieldWage.setText("0");
           textFieldHours.setText("0");
        } else {
            textFieldWage.setText(Integer.toString(current.hourlyWage));
            textFieldHours.setText(Integer.toString(current.hoursWorked));
        }

        recalcEarned();

    }

    /** Create a new employee and add it to the database */
    Employee addNew(int number) {
        Employee e = new Employee();
        e.idNumber = number;
        e.hourlyWage = 0;
        e.hoursWorked = 0;

        db.put(new Integer(number), e);  // Add to the database using (key, value)

        setCurrent(e);

        return e;
    }

    /** Recalculate the text to display in the "Earned income:" label. */
    void recalcEarned() {
        int earned;

        if (current != null)
            earned = current.earnedIncome();
        else
            earned = 0;

        labelEarned.setText(Integer.toString(earned));
    }

}

/** Maintain payroll information for an employee. */
class Employee {
    int idNumber;
    int hourlyWage;
    int hoursWorked;

    int earnedIncome() {
        return hourlyWage * hoursWorked;
    }
}