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POnullPointerException when passing an arrayList to another function?
 

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  1. POnullPointerException when passing an arrayList to another function?
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    <p>in the project im working on, i need to take input from the text box and some selected files from the JFileChooser... i wish to pass the arrayList of files to another class where it has to be processed.. but im getting a nullPointerException here... m new to java so really dont know how to work this out... :-/ plz help!! i have included the indexing class as well:</p> <pre><code> import java.io.*; import java.awt.*; import java.awt.event.*; import java.util.*; import javax.swing.*; //notice javax public class home extends JFrame { JLabel lab=new JLabel("MiniGoogle",JLabel.CENTER); JLabel lab2=new JLabel("Select Files:",JLabel.CENTER); JLabel lab3=new JLabel("Enter Keywords",JLabel.CENTER); JPanel pane = new JPanel(new BorderLayout(0,50)); JButton search = new JButton("Search!"); JTextField kw=new JTextField(25); JButton Browse=new JButton("Browse"); JFileChooser fc= new JFileChooser(); ArrayList files=new ArrayList(); String dest; home() // the frame constructor method { setBounds(100,100,350,350); setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); Container con = this.getContentPane(); // inherit main frame con.add(pane); JPanel s=new JPanel(new FlowLayout()); JPanel r=new JPanel(new FlowLayout()); search.setActionCommand("search"); r.add(lab2); r.add(Browse); r.add(lab3); r.add(kw); pane.add ("North", lab); pane.add ("Center", r); s.add(search); pane.add("South",s); setVisible(true); // display this frame Browse.addActionListener(new ActionListener(){ public void actionPerformed(ActionEvent e) { fc = new JFileChooser(); fc.setMultiSelectionEnabled(true); fc.setCurrentDirectory(new java.io.File("C:/Ananya/Files/DSA/project 2/searchfiles")); fc.setDialogTitle(dest); fc.setFileSelectionMode(JFileChooser.FILES_AND_DIRECTORIES); fc.setAcceptAllFileFilterUsed(false); if (fc.showOpenDialog(fc) == JFileChooser.APPROVE_OPTION) { files.addAll(Arrays.asList(fc.getSelectedFiles())); } else { System.out.println("No Selection "); } } }); search.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent e){ String text=kw.getText(); if(text.equals("")||files==null) { JOptionPane.showMessageDialog(null,"Empty fields!","Error!",JOptionPane.WARNING_MESSAGE); } else { try{ new Indexing(files,text);/*this is where the exception is thrown*/ }catch(Exception ex) { System.out.println(ex+"home"); } } } }); } public static void main(String args[])throws IOException { new home(); } } </code></pre> <p>this is my indexing class:</p> <pre><code>public class Indexing{ HashMap map=new HashMap(); int n; ArrayList temp; String s; public Indexing(ArrayList files,String kw)throws IOException { for(int i=0;i&lt;2;i++) { temp=new ArrayList(50); BufferedReader br = new BufferedReader(new FileReader((File)files.get(i))); String line = "", str = ""; while ((line = br.readLine()) != null) { str += line + " "; } StringTokenizer st = new StringTokenizer(str); while (st.hasMoreTokens()) { temp=new ArrayList(50); s = st.nextToken(); s.trim(); s.toLowerCase(); char ch=s.charAt(s.length()-1); if(!(Character.isLetterOrDigit(ch))) s=s.substring(0,s.length()-1); if(map.get(s)==null) { temp.add(files.get(i)); map.put(s,temp); } else if(!(((ArrayList)map.get(s)).contains(files.get(i)))) { ((ArrayList)map.get(s)).add(files.get(i)); } } } ArrayList result=(ArrayList)map.get(kw); new SearchResults(result,kw); //line 43 } } </code></pre> <p>this is the SearchResults class:</p> <pre><code>import java.awt.*; import java.awt.event.*; import javax.swing.*; import java.io.*; import java.util.*; public class SearchResults { JFrame jtfMainFrame; JLabel msg; JPanel p; JPanel s; File fl; JButton buttons[]; JLabel files[]; public SearchResults(ArrayList results,String kw) { jtfMainFrame = new JFrame(kw+" - MiniGoogle Search"); jtfMainFrame.setSize(50, 50); p=new JPanel(new BorderLayout(0,60)); msg=new JLabel(("Results for "+kw+":"),JLabel.CENTER); p.add("North",msg); s=new JPanel(new FlowLayout()); int l=results.size(); //line 22 for(int i=0;i&lt;l;i++) { fl=(File)results.get(i); files[i].setText((i+1)+"."+ fl); buttons[i]=new JButton("Go!"); s.add(files[i]); s.add(buttons[i]); buttons[i].addActionListener(new ActionListener() { public void actionPerformed(ActionEvent e) { String[] commands = {"cmd", "/c",fl.getAbsolutePath()}; try{Runtime.getRuntime().exec(commands);}catch(Exception ex) { System.out.println(ex); } } }); } p.add("Center",s); p.add("South",msg); jtfMainFrame.setBounds(100,100,350,350); jtfMainFrame.setVisible(true); } public static void main(String[] args) { // Set the look and feel to Java Swing Look try { UIManager.setLookAndFeel(UIManager .getCrossPlatformLookAndFeelClassName()); } catch (Exception e) { System.out.println(e); } } } </code></pre> <p>this is the exception trace:</p> <pre><code> java.lang.NullPointerException at SearchResults.&lt;init&gt;(SearchResults.java:22) at Indexing.&lt;init&gt;(Indexing.java:46) at home$2.actionPerformed(home.java:75) at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1995) at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2318) at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:387) at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:242) at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:236) at java.awt.Component.processMouseEvent(Component.java:6041) at javax.swing.JComponent.processMouseEvent(JComponent.java:3265) at java.awt.Component.processEvent(Component.java:5806) at java.awt.Container.processEvent(Container.java:2058) at java.awt.Component.dispatchEventImpl(Component.java:4413) at java.awt.Container.dispatchEventImpl(Container.java:2116) at java.awt.Component.dispatchEvent(Component.java:4243) at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4322) at java.awt.LightweightDispatcher.processMouseEvent(Container.java:3986) at java.awt.LightweightDispatcher.dispatchEvent(Container.java:3916) at java.awt.Container.dispatchEventImpl(Container.java:2102) at java.awt.Window.dispatchEventImpl(Window.java:2440) at java.awt.Component.dispatchEvent(Component.java:4243) at java.awt.EventQueue.dispatchEvent(EventQueue.java:599) at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:273) at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:183) </code></pre>
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    1. USAnanya Shandilya
    1. USAnanya Shandilya
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    1. COplease include the exception trace and highlight the lines it refers to.
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      1. POnullPointerException when passing an arrayList to another function?
      1. USaioobe
    2. COYou forgot `super()`
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      1. USEng.Fouad
    3. CO@Eng.Fouad, `super()` is inserted implicitly.
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