我收到此错误：
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at graph_traversing.search_string.search_btnActionPerformed(search_string.java:84)
at graph_traversing.search_string.access$000(search_string.java:12)
at graph_traversing.search_string$1.actionPerformed(search_string.java:45)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2018)
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2341)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252)
at java.awt.Component.processMouseEvent(Component.java:6505)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3320)
at java.awt.Component.processEvent(Component.java:6270)
at java.awt.Container.processEvent(Container.java:2229)
at java.awt.Component.dispatchEventImpl(Component.java:4861)
at java.awt.Container.dispatchEventImpl(Container.java:2287)
at java.awt.Component.dispatchEvent(Component.java:4687)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4832)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4492)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4422)
at java.awt.Container.dispatchEventImpl(Container.java:2273)
at java.awt.Window.dispatchEventImpl(Window.java:2719)
at java.awt.Component.dispatchEvent(Component.java:4687)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:735)
at java.awt.EventQueue.access$200(EventQueue.java:103)
at java.awt.EventQueue$3.run(EventQueue.java:694)
at java.awt.EventQueue$3.run(EventQueue.java:692)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87)
at java.awt.EventQueue$4.run(EventQueue.java:708)
at java.awt.EventQueue$4.run(EventQueue.java:706)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:705)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:242)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:161)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:150)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:146)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:138)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:91)
尝试运行此代码时：
package graph_traversing;
import org.neo4j.graphdb.GraphDatabaseService;
import org.neo4j.graphdb.factory.GraphDatabaseFactory;
import org.neo4j.graphdb.index.Index;
import org.neo4j.graphdb.Node;
import org.neo4j.graphdb.Relationship;
import org.neo4j.graphdb.RelationshipType;
public class search_string extends javax.swing.JFrame
{
public search_string() { initComponents(); }
@SuppressWarnings("unchecked")
private static enum RelTypes implements RelationshipType
{
INCLUDES
}
GraphDatabaseService db;
private static final String DB_PATH = "C:\\Users\\fereshteh\\Downloads\\Compressed\\neo4j-community-1.9.4\\DB";
private static Index<Node> nodeIndex;
String [] str;
Node [] nodes;
Relationship rel;
String find;
// <editor-fold defaultstate="collapsed" desc="Generated Code">
private void initComponents() {
jLabel1 = new javax.swing.JLabel();
search_txb = new javax.swing.JTextField();
search_btn = new javax.swing.JButton();
setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
jLabel1.setText(" Enter The Word Please");
search_btn.setText("Search");
search_btn.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
search_btnActionPerformed(evt);
}
});
javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
getContentPane().setLayout(layout);
layout.setHorizontalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addGap(46, 46, 46)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addComponent(search_btn)
.addComponent(jLabel1, javax.swing.GroupLayout.PREFERRED_SIZE, 147, javax.swing.GroupLayout.PREFERRED_SIZE)
.addComponent(search_txb, javax.swing.GroupLayout.PREFERRED_SIZE, 289, javax.swing.GroupLayout.PREFERRED_SIZE))
.addContainerGap(65, Short.MAX_VALUE))
);
layout.setVerticalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addGap(38, 38, 38)
.addComponent(jLabel1, javax.swing.GroupLayout.PREFERRED_SIZE, 36, javax.swing.GroupLayout.PREFERRED_SIZE)
.addGap(39, 39, 39)
.addComponent(search_txb, javax.swing.GroupLayout.PREFERRED_SIZE, 43, javax.swing.GroupLayout.PREFERRED_SIZE)
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, 71, Short.MAX_VALUE)
.addComponent(search_btn)
.addGap(50, 50, 50))
);
pack();
}// </editor-fold>
private void search_btnActionPerformed(java.awt.event.ActionEvent evt) {
str=search_txb.toString().split(" ");
db = new GraphDatabaseFactory().newEmbeddedDatabase( DB_PATH );
for(int i=0;i<str.length;++i)
{
find=str[i];
nodes [i]= nodeIndex.get( "name", find ).getSingle();
}
String s = "hi";
for(int i=0; i<nodes.length; ++i)
{
rel= (Relationship) nodes[i].getRelationships();
for(int j=i+1;j<nodes.length;++j)
{
s=rel.toString();
}
}
System.out.println(s);
}
public static void main(String args[])
{
java.awt.EventQueue.invokeLater(new Runnable() {public void run() {new search_string().setVisible(true);} });
}
// Variables declaration - do not modify
private javax.swing.JLabel jLabel1;
private javax.swing.JButton search_btn;
private javax.swing.JTextField search_txb;
// End of variables declaration
}
我现在第一个错误属于这一行：
nodes [i]= nodeIndex.get( "name", find ).getSingle();
我试图解决它，通过改变它几次但无法解决。
如果您帮助我正确运行代码，那将是您的好意。