Creating a main method?

[Brainz]

I'm creating a simple .java file that has a method called scaleUp, which just increases the size of a picture. The problem I'm having is in creating the main method. The following is what I've come up with:

public class ScaleUp
{

public static Picture main(String[] args)
{

public Picture scaleUp(int numTimes)
{
Picture targetPicture =
new Picture(this.getWidth() * numTimes,
this.getHeight() * numTimes);
Pixel sourcePixel = null;
Pixel targetPixel = null;
int targetX = 0;
int targetY = 0;

for (int sourceX = 0;
sourceX < this.getWidth();
sourceX++)
{
for (int sourceY=0;
sourceY < this.getHeight();
sourceY++)
{
sourcePixel = this.getPixel(sourceX,sourceY);

for (int indexY = 0; indexY < numTimes; indexY++)
{
for (int indexX = 0; indexX < numTimes; indexX++)
{
targetX = sourceX * numTimes + indexX;
targetY = sourceY * numTimes + indexY;
targetPixel = targetPicture.getPixel(targetX,
targetY);
targetPixel.setColor(sourcePixel.getColor());
}
}
}
}

return targetPicture;

}
}
}

When I try to compile the above, I got the following message
3 errors found:
File: C:\Users\Umar\Desktop\ScaleUp.java [line: 7]
Error: C:\Users\Umar\Desktop\ScaleUp.java:7: illegal start of expression
File: C:\Users\Umar\Desktop\ScaleUp.java [line: 7]
Error: C:\Users\Umar\Desktop\ScaleUp.java:7: ';' expected
File: C:\Users\Umar\Desktop\ScaleUp.java [line: 7]
Error: C:\Users\Umar\Desktop\ScaleUp.java:7: ';' expected



What am I doing wrong?
Thanks in advance.

[masijade]

You are declaring a method inside another method. You can't do that.

[JosAH]

public class ScaleUp
{

public static Picture main(String[] args)
  {                          

public Picture scaleUp(int numTimes)
  {
   ...

What am I doing wrong?

You are trying to define a method in the body of another method; Java can't do that. Your class structure has to be like this:

public class ScaleUp {

   public static void main(String[] args) { ... }
   public Picture scaleUp(int numTimes) { ... }
   ...

Note the return type of the main( ... ) method; it has to be void by definition.

kind regards,

Jos

edit: darn, so early in the morning and already too slow ... ;-)

[Brainz]

Thanks for the quick response.
I have another question though, what do I declare after:

public static void main(String[] args) {

I tried this:

public static void main(String[] args) {
String fileName = FileChooser.pickAFile();
     Picture pictObj = new Picture(fileName);                            
}
public Picture scaleUp(int numTimes)
  {...}

but I was returned many errors like the following:

File: C:\Users\Umar\Desktop\ScaleUp.java [line: 10]
Error: C:\Users\Umar\Desktop\ScaleUp.java:10: cannot find symbol
symbol : method getWidth()
location: class ScaleUp

I think I have to refer to my method or an object that can call on the method getWidth(), but I'm not sure how to do this.

Thanks again for the help.

[JosAH]

Thanks for the quick response.
I have another question though, what do I declare after:

public static void main(String[] args) {

I tried this:

public static void main(String[] args) {
String fileName = FileChooser.pickAFile();
     Picture pictObj = new Picture(fileName);                            
}
public Picture scaleUp(int numTimes)
  {...}

but I was returned many errors like the following:

File: C:\Users\Umar\Desktop\ScaleUp.java [line: 10]
Error: C:\Users\Umar\Desktop\ScaleUp.java:10: cannot find symbol
symbol : method getWidth()
location: class ScaleUp

I think I have to refer to my method or an object that can call on the method getWidth(), but I'm not sure how to do this.

Thanks again for the help.

You didn't show us all of the relevant code: the compiler is complaining about the symbol/method getWidth(); it can't find a definition of it but you didn't show us what you had in mind.

kind regards,

Jos

[Brainz]

Sorry about that:

public class ScaleUp
{                 
public static void main(String[] args) {
String fileName = FileChooser.pickAFile();
     Picture pictObj = new Picture(fileName);                            
}
public Picture scaleUp(int numTimes)
  {
    Picture targetPicture = 
      new Picture(this.getWidth() * numTimes,
                  this.getHeight() * numTimes);
    Pixel sourcePixel = null;
    Pixel targetPixel = null;
    int targetX = 0;
    int targetY = 0;
    
    for (int sourceX = 0;
       sourceX < this.getWidth();
       sourceX++)
    {
        for (int sourceY=0;
        sourceY < this.getHeight();
        sourceY++)
    {
          sourcePixel = this.getPixel(sourceX,sourceY);
          
       for (int indexY = 0; indexY < numTimes; indexY++)
      {
         for (int indexX = 0; indexX < numTimes; indexX++)
        {
          targetX = sourceX * numTimes + indexX;
          targetY = sourceY * numTimes + indexY;
          targetPixel = targetPicture.getPixel(targetX,
                                               targetY);
          targetPixel.setColor(sourcePixel.getColor());
        }
      }
    }
  }

  return targetPicture;

}
}

The errors are:
File: C:\Users\Umar\Desktop\ScaleUp.java [line: 10]
Error: C:\Users\Umar\Desktop\ScaleUp.java:10: cannot find symbol
symbol : method getWidth()
location: class ScaleUp
File: C:\Users\Umar\Desktop\ScaleUp.java [line: 11]
Error: C:\Users\Umar\Desktop\ScaleUp.java:11: cannot find symbol
symbol : method getHeight()
location: class ScaleUp
File: C:\Users\Umar\Desktop\ScaleUp.java [line: 18]
Error: C:\Users\Umar\Desktop\ScaleUp.java:18: cannot find symbol
symbol : method getWidth()
location: class ScaleUp
File: C:\Users\Umar\Desktop\ScaleUp.java [line: 22]
Error: C:\Users\Umar\Desktop\ScaleUp.java:22: cannot find symbol
symbol : method getHeight()
location: class ScaleUp
File: C:\Users\Umar\Desktop\ScaleUp.java [line: 25]
Error: C:\Users\Umar\Desktop\ScaleUp.java:25: cannot find symbol
symbol : method getPixel(int,int)
location: class ScaleUp

[masijade]

Because you haven't defined those methods. You are calling "this.getWidth....", which means, of course, that those methods must either be defined in that class, or one its super classes (i.e. some class "up the extension chain"). Since you are not extending anything, and haven't defined the methods here, those methods simply don't exist.

[Brainz]

Thanks! I see what I did there. You guys have been very helpful but I have another question.

My code now is:

public class ScaleUp
{                 
public static void main(String[] args) {
String fileName = FileChooser.pickAFile();
     Picture pictObj = new Picture(fileName);
}
public Picture scaleUp(int numTimes)
  {
  String fileName = FileChooser.pickAFile();
  Picture origPic = new Picture(fileName);
    Picture targetPicture = 
      new Picture(origPic.getWidth() * numTimes,
                  origPic.getHeight() * numTimes);
    Pixel sourcePixel = null;
    Pixel targetPixel = null;
    int targetX = 0;
    int targetY = 0;
    
    for (int sourceX = 0;
       sourceX < origPic.getWidth();
       sourceX++)
    {
        for (int sourceY=0;
        sourceY < origPic.getHeight();
        sourceY++)
    {
          sourcePixel = origPic.getPixel(sourceX,sourceY);
          
       for (int indexY = 0; indexY < numTimes; indexY++)
      {
         for (int indexX = 0; indexX < numTimes; indexX++)
        {
          targetX = sourceX * numTimes + indexX;
          targetY = sourceY * numTimes + indexY;
          targetPixel = targetPicture.getPixel(targetX,
                                               targetY);
          targetPixel.setColor(sourcePixel.getColor());
        }
      }
    }
  }

  return targetPicture;

}
}

It compiles fine but when I type the following to test my program in the interactions pane:

> String fileName = FileChooser.getMediaPath("rose.jpg");
> Picture p = new Picture(fileName);
> p = p.scaleUp(2);

I get this message:
Static Error: No method in Picture has name 'scaleUp'

I'm a little confused because I thought I did create the scaleUp method within the Picture class.

[masijade]

Because it is the class "ScaleUp" that has that method, not the class "Picture".

[Brainz]

Alright. Then can you please explain how I can get the program to actually spit out targetPicture?

[masijade]

Uhm, add the scaleUp method to the Picture class?

Make the scaleUp method static and modify it to also take a "Picture" as a parameter?

[Brainz]

How would I go about modifying it to take a "Picture" as a parameter?

[masijade]

Uhm

public Picture scaleUp(Picture somePic, int numTimes)