My code compiles, but won't run; java.lang.NullPointerException?
My code compiles, its for a Fahrenheit-Celsius converter GUI, but it does not run. The following pops up ...
Exception in thread "main" java.lang.NullPointerException
at Temp1.<init>(Temp1.java:35)
at Temp1.main(Temp1.java:17)
Press any key to continue . . .
This is what my code looks like
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
publicclass Temp1extends JFrameimplements ActionListener{
private JTextField jtfNum, jtfCF, jtfResult, jtfResultCF;
private JButton jbtCelF, jbtFahC, jbtClear, jbtClearBoth, jbtClearNum, jbtClearCF, jbtClose;
privatefloat num1, num2, celfah, fahcel;
privatechar cf;
publicstaticvoid main(String [] args){
Temp1 temp =new Temp1();
temp.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
temp.setSize(800,100);
temp.setTitle("Temperature C/F Converter");
temp.setVisible(true);
}
public Temp1(){
JPanel p1 =new JPanel();
p1.setLayout(new FlowLayout());
p1.add(new JLabel("Degrees : "));
p1.add(jtfNum =new JTextField(10));
p1.add(new JLabel("C/F : "));
p1.add(jtfCF =new JTextField(2));
p1.add(new JLabel("Result : "));
p1.add(jtfResult =new JTextField(10));
jtfResult.setEditable(false);
p1.add(jtfResult =new JTextField(2));
jtfResultCF.setEditable(false);
JPanel p2 =new JPanel();
p2.setLayout(new FlowLayout());
p2.add(jbtCelF =new JButton("Convert to Fahrenheit"));
p2.add(jbtFahC =new JButton("Convert to Celsius"));
p2.add(jbtClose =new JButton("Exit Program"));
p2.add(jbtClearNum =new JButton("Clear Degrees"));
p2.add(jbtClearCF =new JButton("Clear C/F"));
p2.add(jbtClearBoth =new JButton("Clear Degrees and C/F"));
p2.add(jbtClear =new JButton("Clear All"));
getContentPane().setLayout(new BorderLayout());
getContentPane().add(p1, BorderLayout.NORTH);
getContentPane().add(p2, BorderLayout.CENTER);
jbtCelF.addActionListener(this);
jbtFahC.addActionListener(this);
jbtClearNum.addActionListener(this);
jbtClearCF.addActionListener(this);
jbtClearBoth.addActionListener(this);
jbtClear.addActionListener(this);
jbtClose.addActionListener(this);
}
publicvoid actionPerformed(ActionEvent e){
String actionCommand = e.getActionCommand();
if (e.getSource()instanceof JButton){
if ("Convert to Fahrenheit".equals(actionCommand))
calculate1();
if ("Convert to Celsius".equals(actionCommand))
calculate2();
else
if ("Clear All".equals(actionCommand)){
jtfCF.setText(" ");
jtfNum.setText(" ");
jtfResult.setText(" ");
}
if ("Clear Degrees and C/F".equals(actionCommand)){
jtfCF.setText(" ");
jtfNum.setText(" ");
}
if ("Clear Degrees".equals(actionCommand)){
jtfNum.setText(" ");
}
if ("Clear C/F".equals(actionCommand)){
jtfCF.setText(" ");
}
}
else
if ("Exit Program".equals(actionCommand))
System.exit(0);
}
privatevoid calculate1(){
float celfah = ((5/9)*(num1 - 32));
float num1 = (Float.parseFloat(jtfNum.getText().trim()));
char cf = (jtfCF.getText().charAt(0));
if (cf == (' '))
jtfCF.setText("C");
if (cf =='F')
jtfCF.setText("F");
jtfResultCF.setText("F");
jtfResult.setText(" + num 1 + ");
if (cf =='C')
jtfCF.setText("C");
jtfResult.setText(" + celfah + ");
jtfResultCF.setText("F");
}
privatevoid calculate2(){
float fahcel = ((9/5)*(num2) + 32);
float num2 = (Float.parseFloat(jtfNum.getText().trim()));
char cf = (jtfCF.getText().charAt(0));
if (cf == (' '))
jtfCF.setText("C");
if (cf =='C')
jtfResultCF.setText("C");
jtfResult.setText(" + num2 + ");
if (cf =='F')
jtfResult.setText(" + fahcel + ");
jtfResultCF.setText("C");
}
}
