return value for Methods

Question

I am writing a program for my assignment, but for my defaultFan and toString methods I am getting an error stating "invalid method declaration; return type required. However I am unsure what how to resolve this. I tried putting void in front of the two methods and it worked but then I get errors stating I cannot assign variables to final variables slow, medium, and fast. I am not sure if this is correct. How would I fix this?

I also have a hard time using test programs. My professor wants us to use a test program that creates 2 fan objets; the first assign maximum speed, radius 10, color yellow and on status. and the second assign medium speed, radius 5 color blue and off status, and to display the fan objects by invoking their toString methods. Would it be possible for someone to explain how test programs work, and how I would go about creating one for this program. Here is my code:

public class fan {

  private final int slow = 1;
  private final int medium = 2;
  private final int fast = 3;
  private int speed;
  private boolean fanOn;
  private double radius;
  private String color;

  public void defaultFan( )
  {
  int speed = 1;
  boolean fanOn = false;
  double radius = 5;
  String color = "blue";
  }

  public fan(final int slow, final int medium, final int fast, int
speed, boolean fanOn, double radius, String color) {

  this.slow = slow;
  this.medium = medium;
  this.fast = fast;
  this.speed = speed;
  this.fanOn = fanOn;
  this.radius = radius;
  this.color = color;
  }

  public final int getSlow(){
    return slow;
  }

  public final int getMedium() {
    return medium;
  }

  public final int getFast() {
    return fast;
  }

  public int getSpeed() {
    return speed;
  }

  public boolean getfanOn() {
    return fanOn;
  }

  public double getradius() {
    return radius;
  }

  public String getcolor() {
    return color;
  }

  public void setSlow(final int slow) {
    this.slow = slow;
  }

  public void setMedium(final int medium) {
    this.medium = medium;
  }

  public void setFast(final int fast) {
    this.fast = fast;
  }

  public void setSpeed(int speed) {
    this.speed = speed;
  }

  public void setFanOn(boolean fanOn) {
    this.fanOn = fanOn;
  }

  public void setRadius(double radius) {
    this.radius = radius;
  }

  public void setColor(String color) {
    this.color = color;
  }

  public void toString() {
    if(fanOn = true ) {
  System.out.println("The speed of the fan is " + speed + ", the color
of the the fan is " + color + ", and the radius of the fan is " +
radius + ".");
}
  else {
    System.out.println("The fan is off but the color is " + color +"
and the radius is " + radius + ".");
  }

} }

Answer 1

Write your toString method like this

public String toString() {
    String description = "";
    if (fanOn = true) {
        description += "The speed of the fan is " + speed
                + ", the color  of the the fan is " + color
                + ", and the radius of the fan is " + radius + ".";
    } else {
        description += "The fan is off but the color is " + color
                + " and the radius is " + radius + ".";
    }
    return description;
}

I am not sure what you want to do with slow/medium/fast(seems a redundancy with speed). But if you want to modify it, don't declare it as final.

private int slow = 1;
private int medium = 2;
private int fast = 3;

You need a constructor for your test program. (by the way, you should name your class Fan)

public fan(int speed, double radius, String color, boolean fanOn ) {
    this.speed = speed;
    this.radius = radius;
    this.color = color;
    this.fanOn = fanOn;     
}

Your test program should look like this.

public static void main(String args[]) {
    fan fan1 = new fan(100, 100, "red", true);
    fan fan2 = new fan(200, 200, "green", false);
}