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How can I fix a floating decimal error in Java?

I am trying to create a simple program just using the built-in Math methods, but everytime I run it I get a floating decimal error, so I wonder what a floating decimal is and how error occurs.
Here is my code:
private void btnCalculateActionPerformed(java.awt.event.ActionEvent evt) {
double dblSquareRoot = Double.parseDouble(lblSquareRoot.getText());
double dblRandomNumber = Double.parseDouble(lblRandomNumber.getText());
double dblSquareNumber = Double.parseDouble(lblSquareNumber.getText());
double dblRoundUp = Double.parseDouble(lblRoundUp.getText());
double dblRoundDown = Double.parseDouble(lblRoundDown.getText());
lblOutputSquareRoot.setText("" + Math.sqrt(dblSquareRoot));
lblOutputSquareNumber.setText("" + Math.pow(dblSquareNumber, 2));
lblOutputRoundUp.setText("" + Math.ceil(dblRoundUp));
lblOutputRoundDown.setText("" + Math.floor(dblRoundDown));
}
private void btnGenerateActionPerformed(java.awt.event.ActionEvent evt) {
double dblRandomNumber = (Math.random() * 101.0);
txtRandomNumber.setText("" + df.format(dblRandomNumber));
txtSquareRoot.setText("" + df.format(dblRandomNumber));
txtSquareNumber.setText("" + df.format(dblRandomNumber));
txtRoundUp.setText("" + df.format(dblRandomNumber));
txtRoundDown.setText("" + df.format(dblRandomNumber));
df.format = "###.00";
}
error-
Exception in thread "AWT-EventQueue-0" java.lang.NumberFormatException: For input string: "Square Root"
at sun.misc.FloatingDecimal.readJavaFormatString(FloatingDecimal.java:1250)
at java.lang.Double.parseDouble(Double.java:540)
at mathMethods.btnCalculateActionPerformed(mathMethods.java:230)
at mathMethods.access$100(mathMethods.java:13)
at mathMethods$2.actionPerformed(mathMethods.java:97)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2018)
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2341)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252)
at java.awt.Component.processMouseEvent(Component.java:6516)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3320)
at java.awt.Component.processEvent(Component.java:6281)
at java.awt.Container.processEvent(Container.java:2229)
at java.awt.Component.dispatchEventImpl(Component.java:4872)
at java.awt.Container.dispatchEventImpl(Container.java:2287)
at java.awt.Component.dispatchEvent(Component.java:4698)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4832)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4492)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4422)
at java.awt.Container.dispatchEventImpl(Container.java:2273)
at java.awt.Window.dispatchEventImpl(Window.java:2719)
at java.awt.Component.dispatchEvent(Component.java:4698)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:735)
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.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87)
at java.awt.EventQueue$4.run(EventQueue.java:708)
at java.awt.EventQueue$4.run(EventQueue.java:706)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:705)
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)

It looks like you're trying to parse strings from the labels instead of the text fields. Take a look at the variable names.

How to change icon of label with mouse entered event?

Here is the code of mouse entered event of label 1 . And the exception is occuring .I have already worked on previous version but I don't why this happening now.
private void jLabel1MouseEntered(java.awt.event.MouseEvent evt) {
ImageIcon n_cig;
n_cig = new ImageIcon(getClass().getResource("masterproject/Cfull.png"));
jLabel1.setIcon(n_cig);
}
private void jLabel1MouseExited(java.awt.event.MouseEvent evt) {
ImageIcon n_cig;
n_cig = new ImageIcon(getClass().getResource("masterproject/No Cigarretes.png"));
jLabel1.setIcon(n_cig);
}
And the exceptions are here
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at javax.swing.ImageIcon.<init>(ImageIcon.java:205)
at masterproject.design.jButton1ActionPerformed(design.java:384)
at masterproject.design.access$300(design.java:15)
at masterproject.design$3.actionPerformed(design.java:148)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2018)
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2341)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252)
at java.awt.Component.processMouseEvent(Component.java:6505)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3321)
at java.awt.Component.processEvent(Component.java:6270)
at java.awt.Container.processEvent(Container.java:2229)
at java.awt.Component.dispatchEventImpl(Component.java:4861)
at java.awt.Container.dispatchEventImpl(Container.java:2287)
at java.awt.Component.dispatchEvent(Component.java:4687)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4832)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4492)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4422)
at java.awt.Container.dispatchEventImpl(Container.java:2273)
at java.awt.Window.dispatchEventImpl(Window.java:2719)
at java.awt.Component.dispatchEvent(Component.java:4687)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:735)
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.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87)
at java.awt.EventQueue$4.run(EventQueue.java:708)
at java.awt.EventQueue$4.run(EventQueue.java:706)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:705)
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)

The reason that you get a NullPointerException is because for some reason the image file that you're trying to specify cannot be located. So the getResource() method returns a null.
Create a utility function to handle these kind of exception in future
public ImageIcon createImageIcon(String path,
String description) {
java.net.URL imgURL = getClass().getResource(path);
if (imgURL != null) {
return new ImageIcon(imgURL, description);
} else {
System.err.println("Couldn't find file: " + path);
return null;
}
}
Check using this function that wheather or not you are able to access the image or not

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException in Resultset

I'm Trying to run this code to get the ResultSet row by row into an Array so i can put them in a jTable. I don't get why i get this error, i'm new in this.
I would be totally thankfull if you could help me.
try {
int pos = 1;
for (int r=0;r<rsCount;r++){
String[] na = null;
res.absolute(pos);
int a=1;
while(res.next()){
na[a]=res.getString(a+1);
a+=1;
}
pos+=1;
for(int c=0;c<8;c++){
tabla.setValueAt(na[c], r, c);
}
}
} catch (SQLException ex) {
Logger.getLogger(Reporte.class.getName()).log(Level.SEVERE, null, ex);
}
}
And here is the OUTPUT:
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at Main.Reporte.jButton1ActionPerformed(Reporte.java:254)
at Main.Reporte.access$000(Reporte.java:17)
at Main.Reporte$1.actionPerformed(Reporte.java:78)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2018)
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2341)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252)
at java.awt.Component.processMouseEvent(Component.java:6505)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3321)
at java.awt.Component.processEvent(Component.java:6270)
at java.awt.Container.processEvent(Container.java:2229)
at java.awt.Component.dispatchEventImpl(Component.java:4861)
at java.awt.Container.dispatchEventImpl(Container.java:2287)
at java.awt.Component.dispatchEvent(Component.java:4687)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4832)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4492)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4422)
at java.awt.Container.dispatchEventImpl(Container.java:2273)
at java.awt.Window.dispatchEventImpl(Window.java:2719)
at java.awt.Component.dispatchEvent(Component.java:4687)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:729)
at java.awt.EventQueue.access$200(EventQueue.java:103)
at java.awt.EventQueue$3.run(EventQueue.java:688)
at java.awt.EventQueue$3.run(EventQueue.java:686)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87)
at java.awt.EventQueue$4.run(EventQueue.java:702)
at java.awt.EventQueue$4.run(EventQueue.java:700)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:699)
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)

Your string array is not being properly instantiated. You need to instantiate it like:
String[] na = new String[100];
If you don't know how big the array is going to be you might want to consider using an ArrayList
ArrayList<String> na = new ArrayList<String>();
then each string can be added with:
na.add(res.getString(a+1));

AWT-EventQueue-0" java.lang.ArrayIndexOutOfBoundsException

i am a beginner in java, and i am trying to understand the problem in what my friend wrote, the problem from what i think is that the array size are different. if anyone can help it would be much appreciated.
the problem
Exception in thread "AWT-EventQueue-0" java.lang.ArrayIndexOutOfBoundsException: 3
at fmenu$fillbuttonListener.actionPerformed(fmenu.java:115)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2018)
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2341)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252)
at java.awt.Component.processMouseEvent(Component.java:6505)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3320)
at java.awt.Component.processEvent(Component.java:6270)
at java.awt.Container.processEvent(Container.java:2229)
at java.awt.Component.dispatchEventImpl(Component.java:4861)
at java.awt.Container.dispatchEventImpl(Container.java:2287)
at java.awt.Component.dispatchEvent(Component.java:4687)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4832)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4492)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4422)
at java.awt.Container.dispatchEventImpl(Container.java:2273)
at java.awt.Window.dispatchEventImpl(Window.java:2719)
at java.awt.Component.dispatchEvent(Component.java:4687)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:735)
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.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87)
at java.awt.EventQueue$4.run(EventQueue.java:708)
at java.awt.EventQueue$4.run(EventQueue.java:706)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:705)
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)
and here is where i think the problem is
public void actionPerformed(ActionEvent e)
{
Random randomNumbers = new Random();
studentarray = new Object[numofstudent];
quizarray = new Object[numofstudent][numofquiz]; //quizarray = new int[numofstudent][numofquiz]; (original)
for(int i=0; i<numofstudent; i++)
{
quizarray[0][i] = baseid+i;
System.out.println(quizarray[0][i]);
//studentarray[i] = baseid+i;
for(int j=1; j<numofquiz+1; j++)
{
int number = randomNumbers.nextInt(100);
quizarray[j][i] = number; // row column
System.out.println(quizarray[j][i]);
}
}

You define:
quizarray = new Object[numofstudent][numofquiz]
But then access it using
quizarray[0][i]
Where i is < numofstudent. I think you just want:
quizarray[i][0]

Jlist - ClearSelection with observer pattern

This is my first post, I'm having an issue in my application, I'm programing in Java.
I need to implement the observer pattern, because I have a main window and I need to add elements. When I add a element then the main window should be updated. I put the implements and extends Observable and Observer in the right classes and in the main window, I also override the update method. But when the update executes it throws me an exception.
Here is the code and the exeption:
#Override
public void update(Observable o, Object arg) {
// Update Hotels
this.popularHoteles(unDepartamento.getListaHoteles());
}
private void popularHoteles(ArrayList<Hotel> Hoteles) {
listaHoteles.removeAll();
if (fechasCorrectas()) {
listaHoteles.setListData(Hoteles.toArray());
}
}
where "listaHoteles" is a Jlist item on my from.
when i execute the setListDadta i recive this exeption:
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at
diaztaranto.interfaces.MenuPrincipal.listaHotelesValueChanged(MenuPrincipal.java:937)
at
diaztaranto.interfaces.MenuPrincipal.access$800(MenuPrincipal.java:20)
at
diaztaranto.interfaces.MenuPrincipal$9.valueChanged(MenuPrincipal.java:345)
at javax.swing.JList.fireSelectionValueChanged(JList.java:1798) at
javax.swing.JList$ListSelectionHandler.valueChanged(JList.java:1812)
at
javax.swing.DefaultListSelectionModel.fireValueChanged(DefaultListSelectionModel.java:184)
at
javax.swing.DefaultListSelectionModel.fireValueChanged(DefaultListSelectionModel.java:164)
at
javax.swing.DefaultListSelectionModel.fireValueChanged(DefaultListSelectionModel.java:211)
at
javax.swing.DefaultListSelectionModel.changeSelection(DefaultListSelectionModel.java:405)
at
javax.swing.DefaultListSelectionModel.changeSelection(DefaultListSelectionModel.java:415)
at
javax.swing.DefaultListSelectionModel.removeSelectionIntervalImpl(DefaultListSelectionModel.java:576)
at
javax.swing.DefaultListSelectionModel.clearSelection(DefaultListSelectionModel.java:420)
at javax.swing.JList.clearSelection(JList.java:2045) at
diaztaranto.interfaces.MenuPrincipal.popularHoteles(MenuPrincipal.java:998)
at
diaztaranto.interfaces.MenuPrincipal.update(MenuPrincipal.java:1043)
at java.util.Observable.notifyObservers(Observable.java:159) at
java.util.Observable.notifyObservers(Observable.java:115) at
diaztaranto.dominio.Hotel.agregarComentario(Hotel.java:212) at
diaztaranto.interfaces.Evaluacion.botonEvaluarActionPerformed(Evaluacion.java:135)
at diaztaranto.interfaces.Evaluacion.access$000(Evaluacion.java:6)
at
diaztaranto.interfaces.Evaluacion$1.actionPerformed(Evaluacion.java:56)
at
javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2018)
at
javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2341)
at
javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
at
javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
at
javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252)
at java.awt.Component.processMouseEvent(Component.java:6505) at
javax.swing.JComponent.processMouseEvent(JComponent.java:3321) at
java.awt.Component.processEvent(Component.java:6270) at
java.awt.Container.processEvent(Container.java:2229) at
java.awt.Component.dispatchEventImpl(Component.java:4861) at
java.awt.Container.dispatchEventImpl(Container.java:2287) at
java.awt.Component.dispatchEvent(Component.java:4687) at
java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4832)
at
java.awt.LightweightDispatcher.processMouseEvent(Container.java:4492)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4422)
at java.awt.Container.dispatchEventImpl(Container.java:2273) at
java.awt.Window.dispatchEventImpl(Window.java:2719) at
java.awt.Component.dispatchEvent(Component.java:4687) at
java.awt.EventQueue.dispatchEventImpl(EventQueue.java:729) at
java.awt.EventQueue.access$200(EventQueue.java:103) at
java.awt.EventQueue$3.run(EventQueue.java:688) at
java.awt.EventQueue$3.run(EventQueue.java:686) at
java.security.AccessController.doPrivileged(Native Method) at
java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at
java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87)
at java.awt.EventQueue$4.run(EventQueue.java:702) at
java.awt.EventQueue$4.run(EventQueue.java:700) at
java.security.AccessController.doPrivileged(Native Method) at
java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:699) 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)
any one knows why this is happen?
Thanks in advice!