Exception with JRadioButton

[Echilon]

I'm receiving this error at runtime, after entering a value, selecting the 'Binary' checkbox and clicking go. The value prints out to the console OK, but there seems to be a problem with calling the .isSelected() method on the radio button.

Any help is appreciated .

package convertor;
import java.io.*;
import java.util.*;
import java.awt.*;
import javax.swing.*;
import java.awt.event.*;

public class Main {
    private JFrame mainwindow;
    private Container contentpane;
    private Container convtype;
    
    private JButton gobutton;
    private JTextField input;
    private JTextField binaryout;
    private JTextField decimalout;
    private JRadioButton binaryconv;
    
    public Main() {
    }
    
    public static String bin2dec(String input) {
        int len = input.length();
        int power = len-1;
        int total = 0;
        for(int i=0;i<len;i++) {
            int binval = Character.getNumericValue(input.charAt(i));
            total += Math.pow(2,power)*binval;
            power--;
        }
        return ""+total;
    }
    
    public void bin2all(String inputval) {
        decimalout.setText("1"); // bin2dec(inputval));
    }
    
    public void calculate() {
        String inputval = input.getText();
// System.out.println(inputval);
// System.out.println("S"+binaryconv.isSelected());
        if(binaryconv.isSelected()) {
            bin2all(inputval);
        }
    }
    
    public void drawgui() {
        mainwindow = new JFrame();
        mainwindow.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        mainwindow.setLayout(new GridBagLayout());
        GridBagConstraints c = new GridBagConstraints();
        c.fill = GridBagConstraints.HORIZONTAL;
        c.weightx = 0.5;
        c.ipady = 1;
        c.insets = new Insets(1,1,1,1);
        
        JLabel inputlabel = new JLabel("Input:");
        input = new JTextField("");
        c.gridx = 0;
        c.gridy = 0;
        mainwindow.add(inputlabel,c);
        c.gridx = 1;
        mainwindow.add(input,c);
        
        contentpane = new JPanel(new GridLayout(1,4));
        c.gridx = 0;
        c.gridwidth = 2;
        c.gridy = 1;
        JRadioButton binaryconv = new JRadioButton("Binary");
        ButtonGroup ctype = new ButtonGroup();
        ctype.add(binaryconv);
        contentpane.add(binaryconv);
        gobutton = new JButton("Go");
        contentpane.add(gobutton);
        gobutton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) { calculate(); }
        });
        mainwindow.add(contentpane,c);
        
        JLabel binarylabel = new JLabel("Binary:");
        binaryout = new JTextField();
        c.gridx = 0;
        c.gridy = 2;
        mainwindow.add(binarylabel,c);
        c.gridx = 1;
        mainwindow.add(binaryout,c);
        
        mainwindow.pack();
        mainwindow.setVisible(true);
    }
    
    public static void main(String[] args) {
        Main main = new Main();
        main.drawgui();
    }
    
}

Give the error:

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
        at convertor.Main.calculate(Main.java:42)
        at convertor.Main$1.actionPerformed(Main.java:76)
        at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1995)

 

[obadare]

You declared binaryconv twice. Scoping problem

Try changing

JRadioButton binaryconv = new JRadioButton("Binary");

to

binaryconv = new JRadioButton("Binary");

 

[Echilon]

Ah, that fixed it. Thanks.