Mutable jcombobox

Question

People,

I’m working on a vacation record.

The person places the initial date and a combo with the amount of days (10,15, 20 and 30) appears for her to complete it.

Until 30 days of holidays are launched for the employee the screen does not close.(Each iteration adds the amount of the previous until 30) But I wanted the amount of days available on Jcombobox to be changeable. For example I launched 20 days, jcombobox should give only the option of 10. I launched 15 days only option of 15 and releasing 10 days option of 10 and 20. However I cannot clean and re-fix values in the combo.

A Nullpointerexception error appears

if (crt.getSomaQuantidadeFerias(rf.getText(),   ex.getText()) < 30) {
                        int soma = 30 - crt.getSomaQuantidadeFerias(rf.getText(), ex.getText());


                        inicio_ferias.setText("");
                        qtd.setSelectedItem(null);
                        inicio_ferias.setText("");
                        termino_ferias.setText("");
                        tfmes.setText("");
                        try{
                        qtd.removeAllItems();

                        if(soma == 10){
                            qtd.addItem("10");
                            qtd.addItem("20");
                        }else if(soma == 15){
                            qtd.addItem("15");
                        }else if(soma == 20){
                            qtd.addItem("10");
                        }}catch(Exception e){
                            e.printStackTrace();
                            System.out.println(e.getMessage());
                        }

The printStackTrace()

java.lang.NullPointerException
    at view.TelaFerias$4.actionPerformed(TelaFerias.java:439)
    at javax.swing.JComboBox.fireActionEvent(Unknown Source)
    at javax.swing.JComboBox.setSelectedItem(Unknown Source)
    at view.TelaFerias$2.actionPerformed(TelaFerias.java:385)
    at javax.swing.AbstractButton.fireActionPerformed(Unknown Source)
    at javax.swing.AbstractButton$Handler.actionPerformed(Unknown Source)
    at javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source)
    at javax.swing.DefaultButtonModel.setPressed(Unknown Source)
    at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(Unknown Source)
    at java.awt.Component.processMouseEvent(Unknown Source)
    at javax.swing.JComponent.processMouseEvent(Unknown Source)
    at java.awt.Component.processEvent(Unknown Source)
    at java.awt.Container.processEvent(Unknown Source)
    at java.awt.Component.dispatchEventImpl(Unknown Source)
    at java.awt.Container.dispatchEventImpl(Unknown Source)
    at java.awt.Component.dispatchEvent(Unknown Source)
    at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source)
    at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)
    at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)
    at java.awt.Container.dispatchEventImpl(Unknown Source)
    at java.awt.Window.dispatchEventImpl(Unknown Source)
    at java.awt.Component.dispatchEvent(Unknown Source)
    at java.awt.EventQueue.dispatchEvent(Unknown Source)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
    at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
    at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
    at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
    at java.awt.EventDispatchThread.run(Unknown Source)

How can I clear the predefined values and put new ones?

Answer 1

Good for the error this line would be important to analyze:

at javax.swing.JComboBox.setSelectedItem(Unknown Source)

says that the selected value is null,

try to take that line qtd.setSelectedItem(null); and the qtd.removeAllItems(); does not need to be inside the Try...

take a look too if this method crt.getSomaQuantidadeFerias is asking as parameter two strings and returning an integer correctly.