问Java 7多线程叉加入调度程序

EN

public class QuadtreeFindMultiThread extends RecursiveTask<IntArrayList> {
private Quadtree T;
private ObjectArrayList<Node> leaf_nodes;
private ObjectArrayList<Entry> candidatePoints;
private static int POINT_THRESHOLD = 50;
private static int NODE_THRESHOLD = 1;

public QuadtreeFindMultiThread(Quadtree T) {
    this.T = T
    this.leaf_nodes = T.get_nonempty_leaf_nodes();
    this.candidatePoints = new IntArrayList();
}

private QuadtreeFindMultiThread(Quadtree T, IntArrayList leaf_nodes) {
    this.T = T;
    this.leaf_nodes = leaf_nodes; // reference copy
    this.candidatePoints = new IntArrayList();
}

private IntArrayList QuadtreeFind() {
    //...
            //...
            return candidatePoints;
}

private int getPointNum(){
    int count = 0;
    for(Node node:this.leaf_nodes){
        count += node.getAllPoints().size();
    }
    return count;
}
@Override
public IntArrayList compute() {

    if (this.getPointNum() <= POINT_THRESHOLD || this.leaf_nodes.size() <= NODE_THRESHOLD) {// trivial problem, solve by single thread
        this.candidatePoints = QuadtreeFind();

    } else {// START: divide and conquer
    // Divide Step: partition this.leaf_nodes by direction: NW, NE, SW, SE
        Partition leaf_nodes to four quadrants: leaf_nodes_NW,
                    leaf_nodes_NE,
                    leaf_nodes_SW,
                    leaf_nodes_SE



    // Conquer Step
    QuadtreeFindMultiThread thread_NW = new QuadtreeFindMultiThread(
                this.T, leaf_nodes_NW);
    QuadtreeFindMultiThread thread_NE = new QuadtreeFindMultiThread(
                this.T, leaf_nodes_NE);
            QuadtreeFindMultiThread thread_SW = new QuadtreeFindMultiThread(
                this.T, leaf_nodes_SW);
            QuadtreeJoinMultiThread thread_SE = new QuadtreeFindMultiThread(
                this.T, leaf_nodes_SE);
        // fork three new sub threads
        thread_NE.fork();
        thread_SW.fork();
        thread_SE.fork();
        this.candidatePoints.addAll(thread_NW.compute()); // main thread
        this.candidatePoints.addAll(thread_NE.join());
        this.candidatePoints.addAll(thread_SW.join());
        this.candidatePoints.addAll(thread_SE.join());

    }// END: divide and conquer
    return this.candidatePoints;
}


}