java - Wait for library method to finish before continuing -

i have problem. have wait method call library finish before can continue code. how can that? code:

random random = new random(); int node1 = random.nextint(graph.getnumberofvertices() + 1); int node2 = random.nextint(graph.getnumberofvertices() + 1);  matrixwrappedpath path = graph.getshortestpath(node1, node2);  int pathlength = 0; if (path != null) {     pathlength = path.getlength(); } 

the exception i'm getting library (http://grph.inria.fr/javadoc/index.html) is:

exception in thread "main" java.lang.illegalstateexception: cannot compute distance because 2 vertices not connected

at grph.algo.distance.distancematrix.getdistance(distancematrix.java:56)

at grph.matrixwrappedpath.getlength(matrixwrappedpath.java:47)

the distancematrix class runs bfs (org.dipergrafs.algo.bfs.bfsalgorithm) multithreaded (org.dipergrafs.algo.singlesourcesearchalgorithm, method "compute":

public r[] compute(final grph g, intset sources) { final r[] r = createarray(sources.getgreatest() + 1);  new multithreadprocessing(g.getvertices(), grph.getnumberofthreadstocreate()) {      @override     protected void run(int threadid, int source)     {     r[source] = compute(g, source);     }  };  return r; } 

) , fills distancematrix. if distancematrix not finished yet, getdistance(node1, node2) method cannot values distancematrix. read countdownlatch , wait(), notify(), can't figure out how this. way solve this?

you're wrong when assuming there multithreading issue there.

the error message clear :

(...)cannot compute distance because 2 vertices not connected  

you're taking 2 random nodes in graph, these nodes not connected. that's why library cannot compute distance.

are sure didn't forget add edges in graph ? ;)