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javaswingjtextfieldisnullorempty

Swing: the initial String of JTextField is an empty String

About the constructor of JTextField, the javadoc says:

public JTextField()

Constructs a new TextField. A default model is created, the initial string is null, and the number of columns is set to 0.

But when I use this constructor, the method getText() of JTextField returns an empty String, for example:

boolean b = new JTextField().getText().isEmpty();  // returns true.

Why the value returned by getText() is an empty String instead of null?

Solution

  • JTextField get the text from the Document , default implementation PlainDocument never returns null. even though you tried to call JTextField.setText(null), it will just clear the value of the Document content, but still getText will return empty string.