package neo4j;import java.io.File;import java.io.IOException;import javax.management.relation.Relation;import org.neo4j.graphdb.GraphDatabaseService;import org.neo4j.graphdb.Node;import org.neo4j.graphdb.Relationship;import org.neo4j.graphdb.RelationshipType;import org.neo4j.graphdb.Transaction;import org.neo4j.graphdb.factory.GraphDatabaseFactory;import org.neo4j.io.fs.FileUtils;public class test { public enum RelTypes implements RelationshipType{  KNOWS } private static void registerShutdownHook( final GraphDatabaseService graphDb ) {  // Registers a shutdown hook for the Neo4j instance so that it  // shuts down nicely when the VM exits (even if you "Ctrl-C" the  // running example before it's completed)  /*為了確保neo4j數(shù)據(jù)庫的正確關(guān)閉，我們可以添加一個關(guān)閉鉤子方法   * registerShutdownHook。這個方法的意思就是在jvm中增加一個關(guān)閉的   * 鉤子，當(dāng)jvm關(guān)閉的時候，會執(zhí)行系統(tǒng)中已經(jīng)設(shè)置的所有通過方法   * addShutdownHook添加的鉤子，當(dāng)系統(tǒng)執(zhí)行完這些鉤子后，jvm才會關(guān)閉。   * 所以這些鉤子可以在jvm關(guān)閉的時候進行內(nèi)存清理、對象銷毀等操作。*/  Runtime.getRuntime().addShutdownHook( new Thread()  {   @Override   public void run()   {    graphDb.shutdown();   }  } ); } public static void main(String[] args) throws IOException {  FileUtils.deleteRecursively( new File( "db" ) );   GraphDatabaseService graphdb=new GraphDatabaseFactory().newEmbeddedDatabase("db");  Relationship relationship;  Transaction tx=graphdb.beginTx();  try{   Node node1=graphdb.createNode();   Node node2=graphdb.createNode();   node1.setProperty("message", "Hello");   node2.setProperty("message", "World");   relationship = node1.createRelationshipTo(node2, RelTypes.KNOWS);   relationship.setProperty("message", "brave neo4j");   tx.success();   System.out.println("successfully");  }  finally{   tx.finish();  }  registerShutdownHook(graphdb); }}