Task: Barnsley fern
Go: package main

import (
    "image"
    "image/color"
    "image/draw"
    "image/png"
    "log"
    "math/rand"
    "os"
)


const (
    xMin = -2.1820
    xMax = 2.6558
    yMin = 0.
    yMax = 9.9983
)


var (
    width = 200
    n     = int(1e6)
    c     = color.RGBA{34, 139, 34, 255} 
)

func main() {
    dx := xMax - xMin
    dy := yMax - yMin
    fw := float64(width)
    fh := fw * dy / dx
    height := int(fh)
    r := image.Rect(0, 0, width, height)
    img := image.NewRGBA(r)
    draw.Draw(img, r, &image.Uniform{color.White}, image.ZP, draw.Src)
    var x, y float64
    plot := func() {
        
        ix := int(fw * (x - xMin) / dx)
        iy := int(fh * (yMax - y) / dy)
        img.SetRGBA(ix, iy, c)
    }
    plot()
    for i := 0; i < n; i++ {
        switch s := rand.Intn(100); {
        case s < 85:
            x, y =
                .85*x+.04*y,
                -.04*x+.85*y+1.6
        case s < 85+7:
            x, y =
                .2*x-.26*y,
                .23*x+.22*y+1.6
        case s < 85+7+7:
            x, y =
                -.15*x+.28*y,
                .26*x+.24*y+.44
        default:
            x, y = 0, .16*y
        }
        plot()
    }
    
    f, err := os.Create("bf.png")
    if err != nil {
        log.Fatal(err)
    }
    if err := png.Encode(f, img); err != nil {
        log.Fatal(err)
    }
}

Java: import java.awt.*;
import java.awt.image.BufferedImage;
import javax.swing.*;

public class BarnsleyFern extends JPanel {

    BufferedImage img;

    public BarnsleyFern() {
        final int dim = 640;
        setPreferredSize(new Dimension(dim, dim));
        setBackground(Color.white);
        img = new BufferedImage(dim, dim, BufferedImage.TYPE_INT_ARGB);
        createFern(dim, dim);
    }

    void createFern(int w, int h) {
        double x = 0;
        double y = 0;

        for (int i = 0; i < 200_000; i++) {
            double tmpx, tmpy;
            double r = Math.random();

            if (r <= 0.01) {
                tmpx = 0;
                tmpy = 0.16 * y;
            } else if (r <= 0.08) {
                tmpx = 0.2 * x - 0.26 * y;
                tmpy = 0.23 * x + 0.22 * y + 1.6;
            } else if (r <= 0.15) {
                tmpx = -0.15 * x + 0.28 * y;
                tmpy = 0.26 * x + 0.24 * y + 0.44;
            } else {
                tmpx = 0.85 * x + 0.04 * y;
                tmpy = -0.04 * x + 0.85 * y + 1.6;
            }
            x = tmpx;
            y = tmpy;

            img.setRGB((int) Math.round(w / 2 + x * w / 11),
                    (int) Math.round(h - y * h / 11), 0xFF32CD32);
        }
    }

    @Override
    public void paintComponent(Graphics gg) {
        super.paintComponent(gg);
        Graphics2D g = (Graphics2D) gg;
        g.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                RenderingHints.VALUE_ANTIALIAS_ON);

        g.drawImage(img, 0, 0, null);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(() -> {
            JFrame f = new JFrame();
            f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            f.setTitle("Barnsley Fern");
            f.setResizable(false);
            f.add(new BarnsleyFern(), BorderLayout.CENTER);
            f.pack();
            f.setLocationRelativeTo(null);
            f.setVisible(true);
        });
    }
}