How must I initialize a Graphics object?

[crackcrack]

Hi,
I've a problem with Graphics Abstract class;
how must I do to initialize a Graphics object?

I must execute this code:

Graphics gr;
gr.drawString("Image",30,0);
gr.drawString("not",30,30);
gr.drawString("Found",30,60);
image.paintIcon(null,gr,0,0);

the compiler returns my the error:
"gr not initialized"

How can I do to initialize this last?

Thank.