Trailing Deque

.block

height: 600
scrolling: no
border: no
license: cc-by-4.0

ArrayQueue.pde

/**
 * ArrayQueue (v1.1.1)
 * GoToLoop (2020/Apr/20)
 * https://Discourse.Processing.org/t/linkedlist-vs-arraylist/19946/14
 */

//package java.util; // Uncomment this line if this is a ".java" file

import java.util.Collection;
import java.util.Queue;
import java.util.List;
import java.util.ArrayList;
import java.util.Iterator;
import java.io.Serializable;

static // Comment this out if this is a ".java" file
  public class ArrayQueue<E> implements Queue<E>, Cloneable, Serializable {

  //static final long serialVersionUID = 8_779_387_929_858_209_947L;
  static final long serialVersionUID = 779_387_929;

  protected final List<E> list;

  public ArrayQueue() {
    list = new ArrayList<E>();
  }

  public ArrayQueue(final int initialCapacity) { // Ignored by Pjs
    list = new ArrayList<E>(initialCapacity);
  }

  public ArrayQueue(final Collection<? extends E> c) {
    list = new ArrayList<E>(c);
  }

  public void clear() {
    list.clear();
  }

  public int size() {
    return list.size();
  }

  public boolean isEmpty() {
    return list.isEmpty();
  }

  public boolean offer(final E e) {
    return add(e);
  }

  public boolean add(final E e) { // No return (void) on Pjs
    return list.add(e);
  }

  public E peek() {
    return isEmpty()? null : element();
  }

  public E element() {
    return list.get(0);
  }

  public E poll() {
    return isEmpty()? null : remove();
  }

  public E remove() {
    return list.remove(0);
  }

  public boolean remove(final Object o) {
    return list.remove(o);
  }

  public boolean removeAll(final Collection<?> c) {
    return list.removeAll(c);
  }

  public boolean addAll(final Collection<? extends E> c) { // void on Pjs
    return list.addAll(c);
  }

  public boolean retainAll(final Collection<?> c) { // Undefined on Pjs
    return list.retainAll(c);
  }

  public boolean containsAll(final Collection<?> c) { // Undefined on Pjs
    return list.containsAll(c);
  }

  public boolean contains(final Object o) {
    return list.contains(o);
  }

  public Object[] toArray() {
    return list.toArray();
  }

  public <T> T[] toArray(final T[] a) { // Parameter ignored by Pjs
    return list.toArray(a);
  }

  public Iterator<E> iterator() {
    return list.iterator();
  }

  public ArrayQueue<E> clone() {
    return new ArrayQueue<E>(list);
  }

  public String toString() { // Undefined on Pjs
    return list.toString();
  }
}

index.html

<script defer src=https://Unpkg.com/processing-js></script>
<canvas data-processing-sources="Trailing_Deque.pde PointXY.pde ArrayQueue.pde"></canvas>

PointXY.pde

final class PointXY {
  static final color FG = #0000FF;
  static final short BOLD = 3;

  int x, y;

  PointXY(final int px, final int py) {
    setXY(px, py);
  }

  PointXY setXY(final int px, final int py) {
    x = px;
    y = py;
    return this;
  }

  PointXY lineXY(final PointXY other) {
    line(other.x, other.y, x, y);
    return this;
  }

  String toString() {
    return "[ " + x + ", " + y + " ]";
  }
}

Trailing_Deque.pde

/**
 * Trailing Deque (v4.0.0)
 * by  Quarks (2013/Feb)
 * for Rialobran
 * mod GoToLoop
 *
 * https://Forum.Processing.org/two/discussion/3864/
 * how-to-draw-multiple-user-defined-lines#Item_3
 *
 * https://www.OpenProcessing.org/sketch/878488
 * https://Bl.ocks.org/GoToLoop/571eaa4797963ffbacdd706542c30637
 */

import java.util.Queue;
import java.util.ArrayDeque; // not needed anymore

static final boolean JAVA = 1/2 != 1/2.;

static final byte MAX_TRAIL_POINTS = 5;
final Queue<PointXY> trails = new ArrayQueue<PointXY>(MAX_TRAIL_POINTS);
//final Queue<PointXY> trails = new ArrayDeque<PointXY>(MAX_TRAIL_POINTS);

static final color BG  = 0350;
static final short FPS = 30;
static final String GFX = JAVA2D; // use JAVA2D, FX2D or P2D

void setup() {
  size(800, 600, GFX);

  frameRate(FPS);
  noLoop();

  stroke(PointXY.FG);
  strokeWeight(PointXY.BOLD);
}

void draw() {
  background(BG);

  PointXY tt = trails.peek();
  for (final PointXY t : trails)  tt = t.lineXY(tt);

  if (JAVA)  println(trails);
  else { // Pjs doesn't implement ArrayList::toString()
    for (final PointXY xy : trails)  print(xy);
    println("\n");
  }
}

void mousePressed() {
  trails.add( trails.size() == MAX_TRAIL_POINTS
    ? trails.remove().setXY(mouseX, mouseY)
    : new PointXY(mouseX, mouseY) );

  redraw();
}