Java中的ObjectPool

最近在写编辑器(Java+JOGL)的碰撞检测模块，检测函数中，需要用到大量的临时对象，Vector3f, Matrix4f，诸如此类； Java本来就慢，如果我们毫无顾忌的使用　new, 真的是不好意思。。。幸好发现了这个ObjectPool的概念，虽然很简单，但很实用。

/** * * @author Yong.Xue */public class IPoolVec3 { private static ArrayList<Vector3f> objects = new ArrayList<Vector3f>(256); private static int n = 256; public static Vector3f Alloc(float x, float y, float z) { if(n > 0) { Vector3f v = objects.remove(–n); v.set(x, y, z); return v; } else { return new Vector3f(); } } public static Vector3f Alloc() { if(n > 0) { Vector3f v = objects.remove(–n); v.zero(); return v; } else { return new Vector3f(); } } public static void Free(Vector3f v) { if(v == null) { return; } objects.add(v); ++n; }}

使用方法如下

/** * Tests the triangle for interdiv with a ray. * @param ray * @return the distance between the ray origin and the interdiv point */ public float Intersect(IRay ray) { // map tmp vectors to local names Vector3f e1 = IPoolVec3.Alloc(); Vector3f e2 = IPoolVec3.Alloc(); Vector3f p = IPoolVec3.Alloc(); Vector3f q = IPoolVec3.Alloc(); Vector3f s = IPoolVec3.Alloc(); try { // test raydirection e1.sub(m_pvPositions[1], m_pvPositions[0]); e2.sub(m_pvPositions[2], m_pvPositions[0]); p.cross(ray.m_vDirection, e2); float a = e1.dot(p); // if the result is “zero”, the pick ray is parallel to the triangle if ((-IMath.EPSILON < a) && (a < IMath.EPSILON)) { return (-1f); } float f = 1.0f / a; // compute barycentric coordinates s.sub(ray.m_vOrigin, m_pvPositions[0]); final float u = f * s.dot(p); if ((0.0f > u) || (u > 1.0f)) { return (-1f); } q.cross(s, e1); final float v = f * ray.m_vDirection.dot(q); if ((0.0f > u) || (u + v > 1.0f)) { return (-1f); } // compute the interdiv point on the ray final float l = f * e2.dot(q); if (l < 0.0f) { return (-1f); } return (l * l); } finally { IPoolVec3.Free(s); IPoolVec3.Free(q); IPoolVec3.Free(p); IPoolVec3.Free(e2); IPoolVec3.Free(e1); } }

恩，所有的临时对象都不是new，而是从object pool中取得一个引用；如果pool里没有了，才实行new操作；

最重要的一点是，使用完毕后，一定要归还啊，否则就会造成类似C/C++中的内存泄漏，pool中可用元素越来越少。。

蚁穴虽小，溃之千里。