Java beginning if statement in for loop being skipped while others work

Back again with another problem that has stumped me completely and cannot for the life of me fix.

So I had previously posted a question about my Java game I am making for a class that with the help of @MadProgrammer was fixed...mostly. Now there is a new problem that needs a post all to it's own

Previous Post: EDITED: Rows and columns with multidimensional array java

Problem: In the code below I have it set up to loop through the variables x and y to make rows and columns on a jPanel. Each time it loops through it should randomly mark the "x,y" location with one of the "terrains" so that later it can "paint" that location with the appropriate colored 20x20 square.

The code runs great except for one thing, it looks like it skips the very first "if statement" that marks the "terran[0]" which is "floor". When the code is ran it "paints" the other three "terrains" and not a single "floor" "terrain".

I have looked for a solution on these posts but no success:
Java if statement is skipped
If statement being skipped during execution
Java - for loops being skipped
Java if-statement being skipped

Here is a working piece of code that results in the problem at hand:

import java.awt.*;
import javax.swing.*;
import java.util.*;

public class gamePanel extends JPanel
{   

    public gamePanel()
    {
        setBounds(115,93,480,480);
    }

    private Random generator = new Random();    

    int floor = 0; //initializes the variable floor to zero for later use
    int dirt = 1;
    int stone = 2;
    int water = 3;

    int width = 24;
    int height = 24;    
    int x, y; // my x & y variables for coordinates

    int[][] coords = new int[width][height]; //my array that I want to store the coordinates for later use in painting


    int[] terrain = {floor, dirt, stone, water}; //my terrain that will determine the color of the paint

    public void mapGen() //what should mark/generate the JPanel
    {
        for(x = 0; x < width; x++)
        {

            for(y = 0; y < height; y++)
            {

                int z = generator.nextInt(20);// part of the randomization

                if(z <= 10)
                {
                    coords[x][y] = terrain[0]; //should mark the coordinates as floor

                }

                if(z == 11)
                {
                    coords[x][y] = terrain[3];//should mark the coordinates as water
                }

                if(z >= 12 && z <= 16)
                {
                    coords[x][y] = terrain[2];//should mark the coordinates as stone
                }

                if(z >= 17 && z <= 19)
                {
                    coords[x][y] = terrain[1];//should mark the coordinates as dirt
                }

                    coords[0][0] = terrain[0]; // sets coordinate 0,0 to floor //need to have these always be floor
                    coords[23][23] = terrain[0]; // sets coordinate 24,24 to floor //^^^^^^^^^^
            }
        }


    }   


    @Override
    public void paintComponent(Graphics g)//what will paint each 20x20 square on the grid what it is assigned
    {
        super.paintComponent(g);

        for(int x = 0; x < width; x++)
        {
            for(int y = 0; y < height; y++)
            {
                mapGen();

                if(coords[x][y] == terrain[floor])//should paint the floor color at marked coordinates
                {
                    g.setColor(Color.white);
                    g.fillRect((x*20), (y*20), 20, 20); 

                }

                if(coords[x][y] == terrain[dirt]);//should paint the dirt color at marked coordinates
                {
                    g.setColor(new Color(135,102,31));
                    g.fillRect((x*20), (y*20), 20, 20);
                }

                if(coords[x][y] == terrain[stone])//should paint the stone color at marked coordinates
                {
                    g.setColor(new Color(196,196,196));
                    g.fillRect((x*20),(y*20),20,20);
                }

                if(coords[x][y] == terrain[water])//should paint the water color at marked coordinates
                {
                    g.setColor(new Color(85,199,237));
                    g.fillRect((x*20),(y*20),20,20);
                }
            }
        }

    }//end paintComponent

public static void main(String[] args)
{
    gamePanel panel = new gamePanel();
    JFrame frame = new JFrame();
    frame.setSize(500,550);
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.getContentPane().add(panel);
    frame.setVisible(true);

}//end main

}// end gamePanel

Please keep in mind that I am a novice programmer and I am still learning. So anything that is not considered "basic" code please explain in detail.