java - 公开课 DiscoLight 帮助

Question

如果有人能为我的作业指明这段代码的正确方向，我将非常感激。

我已经粘贴了需要完成的整个代码，但我需要以下方法的帮助 public void changeColour(Circle aCircle) 该方法允许随机更改圆圈的颜色，如果 0 到来，圆圈的光应变为红色，1 变为绿色，2 变为紫色。

public class DiscoLight
{
   /* instance variables */
   private Circle light;   // simulates a circular disco light in the Shapes window
   private Random randomNumberGenerator;

   /**
    * Default constructor for objects of class DiscoLight
    */
   public DiscoLight()
   {
      super();
      this.randomNumberGenerator = new Random();           
   }


   /**
    * Returns a randomly generated int between 0 (inclusive) 
    * and number (exclusive). For example if number is 6,
    * the method will return one of 0, 1, 2, 3, 4, or 5.
    */
   public int getRandomInt(int number)
   {
      return this.randomNumberGenerator.nextInt(number);
   }


   /** 
    * student to write code and comment here for setLight(Circle) for Q4(i)
    */
   public void setLight(Circle aCircle)
   {
       this.light = aCircle;

   }


   /**
    * student to write code and comment here for getLight() for Q4(i)
    */
   public Circle getLight()
   {
       return this.light;
   }

   /** 
    * Sets the argument to have a diameter of 50, an xPos 
    * of 122, a yPos of 162 and the colour GREEN.
    * The method then sets the receiver's instance variable
    * light, to the argument aCircle.
    */ 
   public void addLight(Circle aCircle)
   {
      //Student to write code here, Q4(ii)
      this.light = aCircle;
      this.light.setDiameter(50);
      this.light.setXPos(122);
      this.light.setYPos(162);
      this.light.setColour(OUColour.GREEN);
   }


   /** 
    * Randomly sets the colour of the instance variable 
    * light to red, green, or purple.
    */  
   public void changeColour(Circle aCircle)
   {
       //student to write code here, Q4(iii)
       if (getRandomInt() == 0)
       {
           this.light.setColour(OUColour.RED);
       }
       if (this.getRandomInt().equals(1))
       {
           this.light.setColour(OUColour.GREEN);
       }
       else
       if (this.getRandomInt().equals(2))
       {
            this.light.setColour(OUColour.PURPLE);
       }
   }


   /** 
    * Grows the diameter of the circle referenced by the 
    * receiver's instance variable light, to the argument size.  
    * The diameter is incremented in steps of 2,
    * the xPos and yPos are decremented in steps of 1 until the
    * diameter reaches the value given by size. 
    * Between each step there is a random colour change.  The message 
    * delay(anInt) is used to slow down the graphical interface, as required.
    */   
   public void grow(int size)
   {   
       //student to write code here, Q4(iv) 
   }


   /** 
    * Shrinks the diameter of the circle referenced by the 
    * receiver's instance variable light, to the argument size.  
    * The diameter is decremented in steps of 2,
    * the xPos and yPos are incremented in steps of 1 until the
    * diameter reaches the value given by size. 
    * Between each step there is a random colour change.  The message 
    * delay(anInt) is used to slow down the graphical interface, as required.
    */     
   public void shrink(int size)
   {   
       //student to write code here, Q4(v)
   }


   /** 
    * Expands the diameter of the light by the amount given by
    * sizeIncrease (changing colour as it grows).
    * 
    * The method then contracts the light until it reaches its
    * original size (changing colour as it shrinks).
    */     
   public void lightCycle(int sizeIncrease)
   {
      //student to write code here, Q4(vi)
   }


   /** 
    * Prompts the user for number of growing and shrinking
    * cycles. Then prompts the user for the number of units
    * by which to increase the diameter of light.
    * Method then performs the requested growing and 
    * shrinking cycles.
    */     
   public void runLight()
   {  
    //student to write code here, Q4(vii)
   }  


   /**
    * Causes execution to pause by time number of milliseconds
    */
   private void delay(int time)
   {
      try
      {
         Thread.sleep(time); 
      }
      catch (Exception e)
      {
         System.out.println(e);
      } 
   }

}

Answer 1

在//student to write code here下面的第一行调用getRandomInt()时，您忘记传递参数。不过，您的编译器应该已经指出了这一点。

getRandomInt() 方法上方的文档注释告诉您它期望什么作为参数，以及您期望什么作为返回值。

此外，如果您希望灯呈红色、绿色或紫色的机会均等，您应该可以通过单次调用 getRandomInt() 来实现。将值存储在变量中，然后使用 switch 语句打开正确的灯:

int randomValue = getRandomInt(/* I am not telling you what to put here */);

switch (randomValue) {
    case 0: light.setColour(OUColour.RED); break;
    case 1: light.setColour(OUColour.GREEN); break;
    case 2: light.setColour(OUColour.PURPLE); break;
}