Acces bean class property through a JButton

[Kasun Wixkramanayake]

I have tried to assign a value to a bean class property through a jTextfield and retrive it (Using netbeans).

this is the bean class

public class Bean {
    private Double d ;


    public Double getD() {
        return d;
    }

    public void setD(Double d) {
        this.d = d;
    }

}
this is the code that i have written inside the actionevent
private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {
    

b.setD(Double.valueOf(jTextField1.getText()));

System.out.print(b.getD());
    }

but when i try this
the following exception has been thrown
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at se.Log.jButton1ActionPerformed(Log.java:79)
at se.Log.access$000(Log.java:19)
at se.Log$1.actionPerformed(Log.java:46)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1995)
at javax.swing.AbstractButton$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:6038)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3260)
at java.awt.Component.processEvent(Component.java:5803)
at java.awt.Container.processEvent(Container.java:2058)
at java.awt.Component.dispatchEventImpl(Component.java:4410)
at java.awt.Container.dispatchEventImpl(Container.java:2116)
at java.awt.Component.dispatchEvent(Component.java:4240)
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:2429)
at java.awt.Component.dispatchEvent(Component.java:4240)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:599)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:273)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:183)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:173)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:168)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:160)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:121)

[mohammad mahdi ghaseminya]

Hi,
Are You create first object of your bean?
you must create an instance of it in your main class's constructor.

mainClass{

public  mainClass(){
Bean b=new Bean();
}
}

[Ashutosh M Kulkarni]

This is what you could do.

    private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {

        b.setD(Double.valueOf(jTextField1.getText()));
        labelForD.setText(String.valueOf(b.getD()));

    }

Note that above code is not foolproof and in fact, is quite vulnerable. But I have just added one line to your code, to show what could be done. If you are to use this professionally for some project, you might wanna put some checks on what value is entered through jTextField1 because it may contain a lot of special characters, multiple decimal points, letters, etc.

In line 04 (refer code above), I have put a label on the frame which will be modified to whatever value user enters from the textfield.
Please refer to attachment to see an example.

Regards,
Ashutosh

[Kasun Wixkramanayake]

@mohammad mahdi ghaseminya


i have created a bean class instance inside the Action but still get the error message

private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                         
     Bean b=null;

b.setD(Double.valueOf(jTextField1.getText()));

System.out.print(b.getD());
    } 

[mohammad mahdi ghaseminya]

No!
if you create null object you cant reach attributes!
also if you want to use this bean in your main class it is useful to create it in construction,

[Kasun Wixkramanayake]

@mohammad mahdi ghaseminya
thank you brother.it works

[Ashutosh M Kulkarni]

So looks like I made the post for nothing... LOL

never mind.