state pattern in Paint application Java

I have created a Paint application using Controller, Composite(Shapes) and Command(undo/redo) pattern. Now I wanted to modify it and reduce the complexity using state pattern. I know states will be Box/circle/line... transition will be methods to change from 1 state to another.

Snippet of my code:

 public void canvasClicked(int x, int y, Graphics g) {
    switch(this.Click_Button) {
        case Box:
            add()
            break;
        case Circle:
        default:
            add()
            break;
    }
    this.component.draw();
}

What I am confused is where to start with and how to do it. Do I have to remove the composite pattern and do or is it that I am missing something here?

Any references for drawing tool examples will be appreciated as well.

Thank you