Getting user input in Textfield

Question

I have a textfield called "time" in a JPanel, on a JFrame.
When i try getting the user input,
int t = Integer.parseInt(time.getText());
I have a nullpointer exception error.
my code is something like this.
JTextField Time = new JTextField(2);
Time.addActionListener(this);
int t = Integer.parseInt(Time.getText());Is there anything that I miss out?
The above textfield is located in a JPanel, which is located in another JPanel for layout purposes, is that the reason that it cant work?

Answer 1

Is the explanation for the above the same as your last post?
No. The last post (reply 10) was about a way to avoid having to declare a variable, JButton in particular, in class scope.
I did try to explain the answer to you question in reply 11 in reply 9. The comments in the code point out what is happening with the scope to explain why one way works and the other does not.
I'll try again. Let's start with a couple of definitions. A declaration is this
    JTextField Text;where JTextField is the type and Text is the name of the variable. We have declared a variable named Text of type JTextField. Now java knows that any time it encounters the variable Time that it is a JTextField.
Next is instantiation
    Text = new JTextField(2);Here we have instantiated the variable Time and it now points to a real JTextField. You can do both declaration and instantiation at the same time like this
    JTextField Text = new JTextField(2);So on to the issue of scope. Consider your first code block from above
public class MyClient1 extends JFrame implements ActionListener
    JLabel Length;
    JTextField Time;
    JButton Clear, Play;
    public MyClient1()
        JButton Play = new JButton(" Play ");
        Play.addActionListener(this);
        Play.setBounds(410,0,90,20);
        JButton Clear = new JButton(" Clear ");
        Clear.addActionListener(this);
        Clear.setBounds(310,0,90,20);
        JTextField Time = new JTextField(2); //the JTextField is present and it can't work
        Time.addActionListener(this);
        Time.setBounds(80,0,40,20);
        Time.setText("0");
    }You have declared and instantiated the variable Text inside the constructor. This variable is therefore private to this constructor, ie the method whose body is inside the curley braces {...}. No one outside these curley braces can ever know that there exists something called Time. So the code in your actionPerformed method does not have access to Time and when you try to use the variable it will throw a NullPointerException, ie, java is saying it doesn't exist — it is null. You can test this by adding a line like this System.out.println("Test = " + Test); in the actionPerformed method.
The declaration in class scope, ie, this line
    JTextField Time;placed above the constructor is still null because it has not been instantiated.
In the second code block you did instantiate this member variable declaration inside the constructor. They are the same thing, the declaration and the instantiation are referring to the same object. Success! But in the first code block the member variable declaration and the declaration–and–instantiation statement inside the constructor are not even related, they are not the same.
The java tutorial explains this in Scope. They use the word visibility in a more specialized way than I have above.