Add some comments

Author: Josef-Friedrich

jbox2d-library/src/main/java/de/pirckheimer_gymnasium/jbox2d/dynamics/World.java

@@ -2102,7 +2102,6 @@ public void setParticleUserDataBuffer(Object[] buffer, int capacity)
 
     /**
      * Get contacts between particles
-     *
      */
     public ParticleContact[] getParticleContacts()
     {
@@ -2116,7 +2115,6 @@ public int getParticleContactCount()
 
     /**
      * Get contacts between particles and bodies
-     *
      */
     public ParticleBodyContact[] getParticleBodyContacts()
     {
@@ -2130,7 +2128,6 @@ public int getParticleBodyContactCount()
 
     /**
      * Compute the kinetic energy that can be lost by damping force
-     *
      */
     public float computeParticleCollisionEnergy()
     {

jbox2d-library/src/main/java/de/pirckheimer_gymnasium/jbox2d/particle/ParticleBodyContact.java

@@ -30,26 +30,36 @@ public class ParticleBodyContact
 {
     /**
      * Index of the particle making contact.
+     *
+     * @permalink https://github.com/google/liquidfun/blob/7f20402173fd143a3988c921bc384459c6a858f2/liquidfun/Box2D/Box2D/Particle/b2ParticleSystem.h#L101-L102
      */
     public int index;
 
     /**
      * The body making contact.
+     *
+     * @permalink https://github.com/google/liquidfun/blob/7f20402173fd143a3988c921bc384459c6a858f2/liquidfun/Box2D/Box2D/Particle/b2ParticleSystem.h#L104-L105
      */
     public Body body;
 
     /**
      * Weight of the contact. A value between 0.0f and 1.0f.
+     *
+     * @permalink https://github.com/google/liquidfun/blob/7f20402173fd143a3988c921bc384459c6a858f2/liquidfun/Box2D/Box2D/Particle/b2ParticleSystem.h#L110-L111
      */
     float weight;
 
     /**
      * The normalized direction from the particle to the body.
+     *
+     * @permalink https://github.com/google/liquidfun/blob/7f20402173fd143a3988c921bc384459c6a858f2/liquidfun/Box2D/Box2D/Particle/b2ParticleSystem.h#L113-L114
      */
     public final Vec2 normal = new Vec2();
 
     /**
      * The effective mass used in calculating force.
+     *
+     * @permalink https://github.com/google/liquidfun/blob/7f20402173fd143a3988c921bc384459c6a858f2/liquidfun/Box2D/Box2D/Particle/b2ParticleSystem.h#L116-L117
      */
     float mass;
 }

jbox2d-library/src/main/java/de/pirckheimer_gymnasium/jbox2d/particle/ParticleColor.java

@@ -29,6 +29,8 @@
  * Small color object for each particle
  *
  * @author Daniel Murphy
+ *
+ * @permalink https://github.com/google/liquidfun/blob/7f20402173fd143a3988c921bc384459c6a858f2/liquidfun/Box2D/Box2D/Particle/b2Particle.h#L80-L266
  */
 public class ParticleColor
 {
@@ -42,6 +44,17 @@ public ParticleColor()
         a = (byte) 50;
     }
 
+    /**
+     * Constructor with four elements: r (red), g (green), b (blue), and a
+     * (opacity). Each element can be specified 0 to 255.
+     *
+     * @param r red
+     * @param g green
+     * @param b blue
+     * @param a alpha (opacity)
+     *
+     * @permalink https://github.com/google/liquidfun/blob/7f20402173fd143a3988c921bc384459c6a858f2/liquidfun/Box2D/Box2D/Particle/b2Particle.h#L84-L91
+     */
     public ParticleColor(byte r, byte g, byte b, byte a)
     {
         set(r, g, b, a);
@@ -68,11 +81,29 @@ public void set(ParticleColor color)
         a = color.a;
     }
 
+    /**
+     * True when all four color elements equal 0. When true, a particle color
+     * buffer isn't allocated.
+     *
+     * @return True when all four color elements equal 0.
+     *
+     * @permalink https://github.com/google/liquidfun/blob/7f20402173fd143a3988c921bc384459c6a858f2/liquidfun/Box2D/Box2D/Particle/b2Particle.h#L97-L103
+     */
     public boolean isZero()
     {
         return r == 0 && g == 0 && b == 0 && a == 0;
     }
 
+    /**
+     * Sets color for current object using the four elements described above.
+     *
+     * @param r red
+     * @param g green
+     * @param b blue
+     * @param a alpha (opacity)
+     *
+     * @permalink https://github.com/google/liquidfun/blob/7f20402173fd143a3988c921bc384459c6a858f2/liquidfun/Box2D/Box2D/Particle/b2Particle.h#L109-L117
+     */
     public void set(byte r, byte g, byte b, byte a)
     {
         this.r = r;

jbox2d-library/src/main/java/de/pirckheimer_gymnasium/jbox2d/particle/ParticleContact.java

@@ -28,9 +28,14 @@
 public class ParticleContact
 {
     /**
-     * Indices of the respective particles making contact.
+     * Index of the respective particle making contact.
      */
-    public int indexA, indexB;
+    public int indexA;
+
+    /**
+     * Index of the respective particle making contact.
+     */
+    public int indexB;
 
     /**
      * The logical sum of the particle behaviors that have been set.