JOptionPane cancel button doesn't work properly

Question

I am working with JOptionPane. it works great when user clicks on the ok button, but when clicking on the cancel button and when closing the message as well, it displays the error message.

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

    try {
        String num = JOptionPane.showInputDialog("Number to Search:");
        int number = Integer.parseInt(num);
        s.search(number);
   }catch (Exception e) {
        JOptionPane.showMessageDialog(this, "WRONG INPUT: you must insert integers", "Erorr", JOptionPane.ERROR_MESSAGE);
    } 
} 

Answer 1

Use

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

    try {
        String num = JOptionPane.showInputDialog("Number to Search:");
        if(num != null)
        { 
            int number = Integer.parseInt(num);
            s.search(number);
        }
    }catch (Exception e) {
        JOptionPane.showMessageDialog(this, "WRONG INPUT: you must insert integers", "Erorr", JOptionPane.ERROR_MESSAGE);
    } 
} 

JOptionPane returns null when one closes it or presses cancel. So just check this as the above code shows. And an exception will be thrown when you pass null to Integer.parseInt().