You have a scope problem indeed, because statement is a local method variable defined here:
protected void createContents() {
...
Statement statement = null; // local variable
...
btnInsert.addMouseListener(new MouseAdapter() { // anonymous inner class
@Override
public void mouseDown(MouseEvent e) {
...
try {
statement.executeUpdate(query); // local variable out of scope here
} catch (SQLException e1) {
e1.printStackTrace();
}
...
});
}
When you try to access this variable inside mouseDown() method you are trying to access a local variable from within an anonymous inner class and the scope is not enough. So it definitely must be final (which given your code is not possible) or declared as a class member so the inner class can access this statement variable.
Sources:
How to solve it?
You could…
Make statement a class member instead of a local variable:
public class A1 { // Note Java Code Convention, also class name should be meaningful
private Statement statement;
...
}
You could…
Define another final variable and use this one instead, as suggested by @HotLicks:
protected void createContents() {
...
Statement statement = null;
try {
statement = connect.createStatement();
final Statement innerStatement = statement;
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
...
}
But you should…
Reconsider your approach. If statement variable won’t be used until btnInsert button is pressed then it doesn’t make sense to create a connection before this actually happens. You could use all local variables like this:
btnInsert.addMouseListener(new MouseAdapter() {
@Override
public void mouseDown(MouseEvent e) {
try {
Class.forName("com.mysql.jdbc.Driver");
try (Connection connect = DriverManager.getConnection(...);
Statement statement = connect.createStatement()) {
// execute the statement here
} catch (SQLException ex) {
ex.printStackTrace();
}
} catch (ClassNotFoundException ex) {
e.printStackTrace();
}
});