How do I sort an array of objects by their attribute?

cekoivisto

Let's say I define a class with int x and int y, and make an array of instances of that class. How can I sort that array by x values in decreasing order?

GoToLoop

http://docs.Oracle.com/javase/8/docs/api/java/util/Arrays.html#sort-java.lang.Object:A-

http://docs.Oracle.com/javase/8/docs/api/java/lang/Comparable.html

https://forum.Processing.org/two/discussions/tagged?Tag=compareto()

/**
 * Comparable Dots (v1.0)
 * GoToLoop (2017-Feb-19)
 *
 * https://forum.Processing.org/two/discussion/20852/
 * how-do-i-sort-an-array-of-objects-by-their-attribute#Item_1
 */

static final short DOTS = 5;
final Dot[] dots = new Dot[DOTS];

void setup() {
  size(300, 200);
  noLoop();
  for (int i = 0; i < DOTS; dots[i++] = new Dot());
  mousePressed();
}

void draw() {
  background((color) random(#000000));
  frame.setTitle("Frame: " + frameCount);
}

void keyPressed() {
  mousePressed();
}

void mousePressed() {
  for (final Dot d : dots) {
    final int x = (int) random(width);
    final int y = (int) random(height);
    d.setXY(x, y);
  }

  println();
  println(dots);

  java.util.Arrays.sort(dots);
  println(dots);

  redraw = true;
}

class Dot implements Comparable<Dot>, Cloneable {
  short x, y;

  Dot() {
  }

  Dot(final int x, final int y) {
    setXY(x, y);
  }

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

  @Override int compareTo(final Dot d) {
    //return x - d.x; // Ascending
    return d.x - x; // Descending
  }

  @Override int hashCode() {
    return x | y << 020;
  }

  @Override boolean equals(final Object o) {
    return o.hashCode() == hashCode();
  }

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

  @Override Dot clone() {
    try {
      return (Dot) super.clone();
    }
    catch (final CloneNotSupportedException cause) {
      throw new RuntimeException(cause);
    }
  }
}