Processing 3.x not recognizing random() function

I'm trying to create a basic "tree" shape in processing. I have an initial constructor that takes my arguments and draws them in fixed locations on the background, but I also have a secondary constructor that is supposed to assign random values that I specify so that each time it is drawn the trees are in different locations. However, I am having an issue with Processing where it says The function random(int) does not exist and I can't seem to find a solution to the issue.

I realize this is a naive approach to graphics, but I am just trying to get my feet wet with Processing.

My Tree.java class:

import processing.core.PApplet;
import java.util.Random;

public class Tree{

    // Instance variables
    private int centerX, centerY;
    private float scale;
    private int trunkR, trunkG, trunkB, leavesR, leavesG, leavesB;
    private static PApplet sketch;

    public Tree(int theCenterX, int theCenterY, float theScale,
                int theTrunkR, int theTrunkG, int theTrunkB,
                int theLeavesR, int theLeavesG, int theLeavesB)
    {
        centerX = theCenterX;
        centerY = theCenterY;
        scale = theScale;
        trunkR = theTrunkR;
        trunkG = theTrunkG;
        trunkB = theTrunkB;
        leavesR = theLeavesR;
        leavesG = theLeavesG;
        leavesB = theLeavesB;
    }

    public Tree(){
        centerX = random(960.0);
        centerY = random(700.0);
        scale = random(2.0);
        trunkR = random(255.0);
        trunkG = random(255.0);
        trunkB = random(255.0);
        leavesR = random(255.0);
        leavesG = random(255.0);
        leavesB = random(255.0);
    }

    public void draw(){
        sketch.noStroke();
        sketch.fill(trunkR, trunkG, trunkB);
        sketch.rect(centerX, centerY, 80*scale, 300*scale);

        sketch.fill(leavesR, leavesG, leavesB);
        sketch.triangle(centerX - 40*scale, centerY + 40*scale, centerX + 40*scale, centerY - 80*scale, centerX + 120*scale, centerY + 40*scale);
    }

    public static void setup(PApplet theSketch){
        sketch = theSketch;
    }
}

And here is my main class that calls the tree class to create the objects:

Tree tree, tree2, tree3, tree4, randomTree;

void settings(){
    size(1000, 1000);
}

void setup(){
    setupGraphicClasses();

    tree = new Tree(width/2 - 400, height/2 - 100, 1.0, 67, 12, 12, 27, 129, 28);
    tree2 = new Tree(width/2 + 200, height/2 + 150, 1.5, 67, 12, 12, 27, 129, 28);
    tree3 = new Tree(width/2, height/2 - 80, 0.5, 67, 12, 12, 27, 129, 28);
    tree4 = new Tree(width/2 + 320, height/2 - 170, 0.9, 67, 12, 12, 27, 129, 28);
    randomTree = new Tree();
}

void draw() {
    background(127);

    noStroke();
    fill(16, 85, 17);
    rect(0, 500, 1000, 500);
    fill(70, 195, 255);
    rect(0, 0, 1000, 500);
    tree.draw();
    tree4.draw();
    tree2.draw();
    tree3.draw();
    randomTree.draw();
}

public void setupGraphicClasses() {
    Tree.setup(this);
}

Why would I be getting this error? I have tried casting the instance variables as float since those are the parameters the random() function accepts as parameters, but then I get a different error message.