In Processing, which is the fastest way to delete previous text - text

Question

I tried to rewrite text with the backgroud color, but the edge (outline) of the old text remains on the screen. I have no idea why. Can you please help me?
background(-1);
noLoop();
fill(#500F0F);
text("99", 300, 200);
fill(-1);
text("99",300, 200);
Outcome:

Answer 1

In the future, please try to post a MCVE. The code in your post draws the text completely off the screen, which makes me wonder what else is different in your real code. Are you using a draw() function? Please avoid these uncertainties by posting a MCVE.
Anyway, your basic problem is caused by anti-aliasing. By default, Processing uses anti-aliasing to make drawings appear more smooth and less pixelated. You can see this if you zoom in to a drawing and notice the edges are a bit blurry. This is a good thing for most drawings, but in your case it's causing the blurry edges to show through.
So, to fix that problem, you could disable anti-aliasing by calling the noSmooth() function:
size(500, 500);
noSmooth();
background(255);
noLoop();
fill(#500F0F);
text("99", 300, 200);
fill(255);
text("99",300, 200);
Also notice that I'm using 255 as a paramter instead of -1. I'm not sure what a color parameter of -1 is supposed to do, so I'd keep it between 0 and 255 just to be safe.
But it's a little fishy that you need to "delete" any text in the first place. Like George's comment says, why don't you just call the background() function to clear out old frames?
Here's a small example:
void draw() {
background(64);
if (mousePressed) {
text("hello", 20, 40);
}
}