构造函数必须调用super（）或this（）

Question

Can anyone help me with the following error report (for the code at the bottom):

Exception in thread "AWT-EventQueue-0" java.lang.VerifyError: Constructor must call super() or this() before return in method org.jfree.ui.RectangleInsets.<init>()V at offset 0
at org.jfree.chart.axis.Axis.<clinit>(Axis.java:153)
at org.jfree.chart.StandardChartTheme.<init>(StandardChartTheme.java:233)
at org.jfree.chart.StandardChartTheme.<init>(StandardChartTheme.java:319)
at org.jfree.chart.ChartFactory.<clinit>(ChartFactory.java:231)
at odesolver.ODESolver.createGraph(ODESolver.java:81)
at odesolver.ODESolver.<init>(ODESolver.java:35)
at odesolver.ODESolver$2.run(ODESolver.java:105)
at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:251)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:733)
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.awt.EventQueue.dispatchEvent(EventQueue.java:703)
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)
BUILD SUCCESSFUL (total time: 2 seconds)  

which relates to the following 3 lines of the code:

ODESolver.java:81

JFreeChart chart = ChartFactory.createXYLineChart(

ODESolver.java:35

createGraph();

ODESolver.java:105

new ODESolver(); // Let the constructor do the job

Whole program:

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */
package odesolver;

/**
 *
 * @author User
 */
import java.awt.*;       // Using AWT containers and components
import java.awt.event.*; // Using AWT events and listener interfaces
import javax.swing.*;    // Using Swing components and containers
import org.jfree.data.xy.XYSeries;
import org.jfree.data.xy.XYSeriesCollection;
import org.jfree.chart.JFreeChart;
import org.jfree.chart.ChartFactory;
import org.jfree.chart.plot.PlotOrientation;
import org.jfree.chart.ChartPanel;
import org.jfree.data.general.Series;

// A Swing GUI application inherits the top-level container javax.swing.JFrame
public class ODESolver extends JFrame {
   private JTextField tfInput, tfOutput;
   private int numberIn;   // input number
   private int sum = 0;    // accumulated sum, init to 0

   /** Constructor to setup the GUI */
   public ODESolver() {
      // Retrieve the content-pane of the top-level container JFrame
      // All operations done on the content-pane
      Container cp = getContentPane();
      cp.setLayout(new GridLayout(2, 2, 5, 5));

      createGraph();


      add(new JLabel("Enter an Integer: "));
      tfInput = new JTextField(10);
      add(tfInput);
      add(new JLabel("The Accumulated Sum is: "));
      tfOutput = new JTextField(10);
      tfOutput.setEditable(false);  // read-only
      add(tfOutput);

      // Allocate an anonymous instance of an anonymous inner class that
      //  implements ActionListener as ActionEvent listener
      tfInput.addActionListener(new ActionListener() {
         @Override
         public void actionPerformed(ActionEvent e) {
            // Get the String entered into the input TextField, convert to int
            numberIn = Integer.parseInt(tfInput.getText());
            sum += numberIn;      // accumulate numbers entered into sum
            tfInput.setText("");  // clear input TextField
            tfOutput.setText(sum + ""); // display sum on the output TextField
         }
      });

      setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);  // Exit program if close-window button clicked
      setTitle("ODE Accumulator"); // "this" Frame sets title
      setSize(350, 120);  // "this" Frame sets initial size
      setVisible(true);   // "this" Frame shows


   }

   private JPanel createGraph() {

        JPanel panel = new JPanel();
        XYSeries series = new XYSeries("MyGraph");
        series.add(0, 1);
        series.add(1, 2);
        series.add(2, 5);
        series.add(7, 8);
        series.add(9, 10);


        XYSeriesCollection dataset = new XYSeriesCollection();
        dataset.addSeries(series);

        JFreeChart chart = ChartFactory.createXYLineChart(
                "XY Chart",
                "x-axis",
                "y-axis",
                dataset, 
                PlotOrientation.VERTICAL,
                true,
                true,
                false
                );
        ChartPanel chartPanel = new ChartPanel(chart);


        panel.add(chartPanel);

        return panel;
    }

   /** The entry main() method */
   public static void main(String[] args) {
      // Run the GUI construction in the Event-Dispatching thread for thread-safety
      SwingUtilities.invokeLater(new Runnable() {
         @Override
         public void run() {
            new ODESolver(); // Let the constructor do the job
         }
      });
   }
}

Maybe the problem is that there are files in ODESolver, src and lib with errors, as netbeans reports (see screenshot below). I don't know which files are upposed to have errors though, as none of then have an exclamation mark on them, as they usually do of they have errors.

Answer 1

You appear to be running an old version of JFreeChart which produces this error. Upgrade to version 1.0.13 as found here

Answer 2

通过将jar文件添加到类路径（而不是包含它们的文件夹）解决了问题

Answer 3

The various constructors of JFrame do important initialisation work, that any JFrame requires. Therefore, every JFrame that is ever created must have one of those constructors called. But because an ODESolver is also a JFrame , that applies to ODESolver objects too.

Fortunately, the Java language enforces this. We can't create an ODESolver , without one of the JFrame constructors getting called. The way it enforces it is by requiring every ODESolver constructor to be mapped to a JFrame constructor.

When we create an ODESolver , one of the ODESolver constructors will get called. But that constructor must specify which JFrame constructor will get called. The way it does that is by doing one of the following.

• specifying explicitly which JFrame constructor to use, via a call to super() , with or without some arguments;
• calling another ODESolver constructor, via a call to this() , with or without some arguments.

In either case, the call to super() or this() must be the first line of the ODESolver constructor.