GRAPHICAL USER INTERFACE (GUI) AND OBJECT-ORIENTED DESIGN (OOD) - Java Programming: From Problem Analysis to Program Design - page 344

TABLE 6-4 Some Methods of the class JTextField (continued)

Method / Description

public JTextField(String str, int columns)
//Constructor to initialize the object with the text specified
//by str and to set the size of the text field.

public void setText(String str)
//Method to set the text of the text field to the string specified
//by str.

public String getText()
//Method to return the text contained in the text field.

public void setEditable( boolean b)
//If the value of the boolean variable b is false, the user cannot
//type in the text field.
//In this case, the text field is used as a tool to display
//the result.

public void addActionListener(ActionListener obj)
//Method to register a listener object to a JTextField.

Consider the following statements:

private JTextField lengthTF, widthTF, areaTF,
perimeterTF; //Line 1

lengthTF = new JTextField(10); //Line 2
widthTF = new JTextField(10); //Line 3
areaTF = new JTextField(10); //Line 4
perimeterTF = new JTextField(10); //Line 5
The statement in Line 1 declares four reference variables, lengthTF , widthTF , areaTF ,and
perimeterTF ,oftype JTextField . The statement in Line 2 instantiates the
object lengthTF and sets the width of this text field to 10 characters. That is, this text field
can display no more than 10 characters. The meaning of the other statements is similar.
Placing these objects involves using the add method of the class Container as described
in the previous section. The following statements add these components to the container: