How to use org.jbox2d.collision

public void writeCache(SimplexCache cache) {
 cache.metric = getMetric();
 cache.count = m_count;
 for (int i = 0; i < m_count; ++i) {
  cache.indexA[i] = (vertices[i].indexA);
  cache.indexB[i] = (vertices[i].indexB);
 }
}

public EPCollider() {
 for (int i = 0; i < 2; i++) {
  ie[i] = new ClipVertex();
  clipPoints1[i] = new ClipVertex();
  clipPoints2[i] = new ClipVertex();
 }
}

 @Override
 public int compareTo(ContactID o) {
  return getKey() - o.getKey();
 }
}

public DefaultWorldPool(int argSize, int argContainerSize) {
 vecs = new OrderedStack<Vec2>(argSize, argContainerSize) {
  protected Vec2 newInstance() { return new Vec2(); }
 };
 vec3s = new OrderedStack<Vec3>(argSize, argContainerSize) {
  protected Vec3 newInstance() { return new Vec3(); }
 };
 mats = new OrderedStack<Mat22>(argSize, argContainerSize) {
  protected Mat22 newInstance() { return new Mat22(); }
 };
 aabbs = new OrderedStack<AABB>(argSize, argContainerSize) {
  protected AABB newInstance() { return new AABB(); }
 };
 rots = new OrderedStack<Rot>(argSize, argContainerSize) {
  protected Rot newInstance() { return new Rot(); }
 };
 mat33s = new OrderedStack<Mat33>(argSize, argContainerSize) {
  protected Mat33 newInstance() { return new Mat33(); }
 };
 dist = new Distance();
 collision = new Collision(this);
 toi = new TimeOfImpact(this);
}

 protected AABB newInstance() { return new AABB(); }
};

/**
 * Blank manifold point with everything zeroed out.
 */
public ManifoldPoint() {
  localPoint = new Vec2();
  normalImpulse = tangentImpulse = 0f;
  id = new ContactID();
}

/**
 * @deprecated please use {@link #raycast(RayCastOutput, RayCastInput, IWorldPool)} for better
 *             performance
 * @param output
 * @param input
 * @return
 */
public final boolean raycast(final RayCastOutput output, final RayCastInput input) {
 return raycast(output, input, new DefaultWorldPool(4, 4));
}

public ContactID(final ContactID c) {
 set(c);
}

@Override
public float getAreaRatio() {
 if (m_root == NULL_NODE) {
  return 0.0f;
 }
 final int root = m_root;
 float rootArea = m_aabb[root].getPerimeter();
 float totalArea = 0.0f;
 for (int i = 0; i < m_nodeCapacity; ++i) {
  if (m_height[i] < 0) {
   // Free node in pool
   continue;
  }
  totalArea += m_aabb[i].getPerimeter();
 }
 return totalArea / rootArea;
}

public void collideEdgeAndPolygon(Manifold manifold, final EdgeShape edgeA, final Transform xfA,
  final PolygonShape polygonB, final Transform xfB) {
 collider.collide(manifold, edgeA, xfA, polygonB, xfB);
}

/**
 * creates a manifold with 0 points, with it's points array full of instantiated ManifoldPoints.
 */
public Manifold() {
 points = new ManifoldPoint[Settings.maxManifoldPoints];
 for (int i = 0; i < Settings.maxManifoldPoints; i++) {
  points[i] = new ManifoldPoint();
 }
 localNormal = new Vec2();
 localPoint = new Vec2();
 pointCount = 0;
}

protected Contact(IWorldPool argPool) {
 m_fixtureA = null;
 m_fixtureB = null;
 m_nodeA = new ContactEdge();
 m_nodeB = new ContactEdge();
 m_manifold = new Manifold();
 pool = argPool;
}

 /**
  * copies this manifold from the given one
  * 
  * @param cp manifold to copy from
  */
 public void set(Manifold cp) {
  for (int i = 0; i < cp.pointCount; i++) {
   points[i].set(cp.points[i]);
  }

  type = cp.type;
  localNormal.set(cp.localNormal);
  localPoint.set(cp.localPoint);
  pointCount = cp.pointCount;
 }
}

public boolean isEqual(final ContactID cid) {
 return getKey() == cid.getKey();
}

/**
 * Creates a manifold point as a copy of the given point
 * @param cp point to copy from
 */
public ManifoldPoint(final ManifoldPoint cp) {
  localPoint = cp.localPoint.clone();
  normalImpulse = cp.normalImpulse;
  tangentImpulse = cp.tangentImpulse;
  id = new ContactID(cp.id);
}

public Collision(IWorldPool argPool) {
 incidentEdge[0] = new ClipVertex();
 incidentEdge[1] = new ClipVertex();
 clipPoints1[0] = new ClipVertex();
 clipPoints1[1] = new ClipVertex();
 clipPoints2[0] = new ClipVertex();
 clipPoints2[1] = new ClipVertex();
 pool = argPool;
}

  /**
   * Sets this manifold point form the given one
   * @param cp the point to copy from
   */
  public void set(final ManifoldPoint cp){
    localPoint.set(cp.localPoint);
    normalImpulse = cp.normalImpulse;
    tangentImpulse = cp.tangentImpulse;
    id.set(cp.id);
  }
}

@Override
public float getAreaRatio() {
 if (m_root == null) {
  return 0.0f;
 }
 final DynamicTreeNode root = m_root;
 float rootArea = root.aabb.getPerimeter();
 float totalArea = 0.0f;
 for (int i = 0; i < m_nodeCapacity; ++i) {
  final DynamicTreeNode node = m_nodes[i];
  if (node.height < 0) {
   // Free node in pool
   continue;
  }
  totalArea += node.aabb.getPerimeter();
 }
 return totalArea / rootArea;
}

public ManifoldPoint[] getPoints () {
  for (int i = 0; i < manifold.points.length; i++) {
    points[i].contactID = manifold.points[i].id.getKey();
    points[i].localPoint.set(manifold.points[i].localPoint.x, manifold.points[i].localPoint.y);
    points[i].normalImpulse = manifold.points[i].normalImpulse;
    points[i].tangentImpulse = manifold.points[i].tangentImpulse;
  }
  return points;
}

public ClipVertex() {
 v = new Vec2();
 id = new ContactID();
}