Three types of data entry fields appear in BreezySwing: IntegerField, and DoubleField, and JTextField (actually, a built-in class in javax.swing). As the names imply, each type of field is suited for the input and output of a specific type of data. In the case of the numeric fields, conversion between numbers and text is handled internally within the field object. Thus, the input method getNumber returns a number, whereas the output method setNumber expects a numeric argument, when used with the numeric fields. The DoubleField method setPrecision is available to modify the precision used to display floating-point numbers. The methods getText and setText are used to read and write strings with text fields. The data entry field methods are summarized in the next table:
| Field Type | Method | What it does |
| IntegerField, DoubleField |
getNumber() | Returns (as input) the number contained in the field. |
| isValidNumber() | Returns true if the contents of the field represent a valid number, or false otherwise. | |
| setNumber(number) | Outputs the number to the field. | |
| DoubleField | setPrecision(width) | Sets the number of digits to display to right of the decimal point. |
| JTextField | getText() | Returns (as input) the string contained in the field. |
| setText(text) | Outputs the string to the field. |
To make a data entry field read-only, you call the method setEditable(false) on the field.
Note that the input method getNumber returns 0 and resets the field’s data to 0 if the user has entered a number with an invalid format (such as bad digits). This type of error can be detected under program control, before calling getNumber, by calling the method isValidNumber on the field.