q1

public class RGBColor
{
    private int _red,_green,_blue;

    final int MIN_VALUE = 0, MAX_VALUE = 255;

    //constructors
    public RGBColor()//default constructor, black.
    {
     _red = 0;
     _green = 0;
     _blue = 0;
    }

    public RGBColor(int red, int green, int blue)
    {
     if(isValid(red) && isValid(green) && isValid(blue))
     {
      _red = red;
      _green = green;
      _blue = blue;
     }
     else
     {
      _red = 0;
      _green = 0;
      _blue = 0;
     }
    }

    public RGBColor(RGBColor other)
    {
     _red = other._red;
     _green = other._green;
     _blue = other._blue;
    }

    private boolean isValid(int num)
    {
     if(num < MIN_VALUE ||num > MAX_VALUE)
       return false;
     return true;
    }

    public int getRed()
    {
     return _red;
    }

    public int getGreen()
    {
     return _green;
    }

    public int getBlue()
    {
     return _blue;
    }

    public void setRed(int num)
    {
     if(isValid(_red))
      _red = num;
     return;
    }

    public void setGreen(int num)
    {
     if(isValid(_green))
      _green = num;
     return;
    }

    public void setBlue(int num)
    {
     if(isValid(_blue))
      _blue = num;
     return;
    }

    public String toString()
    {
     return "(" + _red + "," + _green + "," + _blue + ")";
    }

    public boolean equals(RGBColor other)
    {
     if(_red == other._red && _green == other._green && _blue == other._blue)
       return true;
     return false;
    }

    public void mix(RGBColor other)
    {
     _red = Average(_red,other._red);
     _green = Average(_green,other._green);
     _blue = Average(_blue,other._blue);
    }

    private int Average(int num1, int num2)
    {
     return (num1 + num2)/2;
    }

    public double convertToGrayscale()
    {
    return 0.3 * _red + 0.59 * _green + 0.11 * _blue;
    }

    public void invert()
    {
    _red = MAX_VALUE - _red;
    _green = MAX_VALUE - _green;
    _blue = MAX_VALUE - _blue;
    }















}