線程“ AWT-EventQueue-0”中的異常java.lang.NumberFormatException：空字符串OS內核模擬

Question

我正在用GUI在Java中進行OS內核仿真的項目。 我創建了一個Jtable，用於添加流程（任務）。 現在，我嘗試使用FIFO（先進先出）算法執行進程。 我正在嘗試實現Button功能，以使用fifo算法執行進程。 按下按鈕后，在這里引發了以下異常。

Exception in thread "AWT-EventQueue-0" java.lang.NumberFormatException: empty String

我在以下功能中可能在這里做錯了

private void fifo_BtnActionPerformed(java.awt.event.ActionEvent evt) {
    //DefaultTableModel model = (DefaultTableModel) processTable.getModel();

    int totalNoOfProcess = p.totalProcess();

    for (int i = 0; i < totalNoOfProcess; i++) {
        Process cp = p.getPCB(i);

        double burstTime = cp.getBurst_time();

        while (burstTime > 0) {
            burstTime = burstTime - cpuTime;
            cp.setStatus("running");

            DefaultTableModel newRow = new DefaultTableModel();
            newRow.equals(model);

            newRow.setValueAt(new Object[]{
                (Double.parseDouble(processID_TF.getText())), processNameTF.getText(), Double.parseDouble(burstTimeTF.getText()), Double.parseDouble(priorityTF.getText()), statusTF.getText().trim()
            },i, i);

            //newRow.addRow(new Object[] {(Double.parseDouble(processID_TF.getText())), processNameTF.getText(), Double.parseDouble(burstTimeTF.getText()), Double.parseDouble(priorityTF.getText()), statusTF.getText().trim()});
            model.removeRow(i);
            //model.setValueAt(newRow, i, i);

            for (int a = 0; a < 100; a++) {
                model.fireTableDataChanged();
            }
        }
        cp.setBurst_time(0);
        cp.setStatus("Completed");
        DefaultTableModel anotherRow = new DefaultTableModel();
        anotherRow.equals(model);

        anotherRow.addRow(new Object[] {
            (Double.parseDouble(processID_TF.getText())), processNameTF.getText(), Double.parseDouble(burstTimeTF.getText()), Double.parseDouble(priorityTF.getText()), statusTF.getText().trim()
        });
        model.removeRow(i);
        model.setValueAt(anotherRow, i, i);
        model.fireTableDataChanged();
    }
}

這是我的add_processes函數

private void add_processBtnActionPerformed(java.awt.event.ActionEvent evt)     
{   
    p.createPCB((Double.parseDouble(processID_TF.getText())), processNameTF.getText(), Double.parseDouble(burstTimeTF.getText()), Double.parseDouble(priorityTF.getText()), statusTF.getText().trim());

    Process process = p.getPCB(count);

    process.setId(Double.parseDouble(processID_TF.getText()));
    process.setName(processNameTF.getText().trim());
    process.setBurst_time(Double.parseDouble(burstTimeTF.getText()));
    process.setPriority(Double.parseDouble(priorityTF.getText()));
    process.setStatus(statusTF.getText());

    model.addRow(new Object[]{process.getId(), process.getName(), process.getBurst_time(), process.getPriority(), process.getStatus()});

    //model.fireTableDataChanged();
    processID_TF.setText("");
    processNameTF.setText("");
    burstTimeTF.setText("");
    priorityTF.setText("");

    count++;
}     

這是按下fifo按鈕后引發的整個異常錯誤。 添加過程功能正常

Exception in thread "AWT-EventQueue-0" java.lang.NumberFormatException: empty String
    at sun.misc.FloatingDecimal.readJavaFormatString(FloatingDecimal.java:992)
    at java.lang.Double.parseDouble(Double.java:510)
    at ahmed.riphah.OS.ProcessManagementGUI.fifo_BtnActionPerformed(ProcessManagementGUI.java:251)
    at ahmed.riphah.OS.ProcessManagementGUI.access$100(ProcessManagementGUI.java:14)
    at ahmed.riphah.OS.ProcessManagementGUI$2.actionPerformed(ProcessManagementGUI.java:96)
    at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1995)
    at javax.swing.AbstractButton$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:6297)
    at javax.swing.JComponent.processMouseEvent(JComponent.java:3275)
    at java.awt.Component.processEvent(Component.java:6062)
    at java.awt.Container.processEvent(Container.java:2039)
    at java.awt.Component.dispatchEventImpl(Component.java:4660)
    at java.awt.Container.dispatchEventImpl(Container.java:2097)
    at java.awt.Component.dispatchEvent(Component.java:4488)
    at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4575)
    at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4236)
    at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4166)
    at java.awt.Container.dispatchEventImpl(Container.java:2083)
    at java.awt.Window.dispatchEventImpl(Window.java:2489)
    at java.awt.Component.dispatchEvent(Component.java:4488)
    at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:668)
    at java.awt.EventQueue.access$400(EventQueue.java:81)
    at java.awt.EventQueue$2.run(EventQueue.java:627)
    at java.awt.EventQueue$2.run(EventQueue.java:625)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:87)
    at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:98)
    at java.awt.EventQueue$3.run(EventQueue.java:641)
    at java.awt.EventQueue$3.run(EventQueue.java:639)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:87)
    at java.awt.EventQueue.dispatchEvent(EventQueue.java:638)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269)
    at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161)
    at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)

Answer 1

當您單擊該按鈕時，GUI中的文本字段之一為空，從而導致：

Double.parseDouble( aTextField.getText() );

失敗（這是異常告訴您的內容）。

因此，有兩種情況：

• 要么必須填寫文本字段，在這種情況下，您可以在單擊按鈕時驗證是否正確設置了所有字段。

例如：

if( processID_TF.getText().match("\\d+") ){
   // proceed with normal behaviour
}else{
   JOptionPane.showMessageDialog(null, "You must indicate a correct process ID.");
}

• 或者該字段是可選的，在這種情況下，您可以在上面的代碼行周圍使用try / catch塊，並在catch塊中設置默認值。

例如：

double value;
try{
    value = Double.parseDouble(processID_TF.getText());
}catch(Exception e){
    value = 0.; // Default value
}