Java Reference
In-Depth Information
p . It must be the case that the border layout is selected as the layout for the panel. The
method can also be applied on objects of type JFrame . Note that only one component
can be added to each of the five areas. For example, if a second button is added to
the west part of the window, it will be placed on top of the first button.
p.setLayout(new GridLayout(3,5,2,1));
Creates a new grid layout. The layout
will have 3 rows, 5 columns, a 2-pixel horizontal gap, and 1-pixel vertical gap.
￿ String s = new ScriptEngineManager().getEngineByName("JavaScript").
Computes the value of the expression e . For example, if e is the string
"2+2" , then the value of s will become the string "4" .
JLabel l = new JLabel("This is a label");
Creates a new label with text
￿ JTextField f = new JTextField("",20);
Creates a text field of size 20 charac-
ters. The first parameter is the initial text in the text field.
Gets the text in the text field.
String s = f.getText();
￿ f.setText("new text");
Sets the text of the text field.
￿ f.setFont(new Font("SansSerif", Font.BOLD,10));
Changes the font of the
text field f . The method also applies to text areas. The new font will be Sans Serif,
bold, and point size 10.
Adds a document listener to the
text field. The document listener interface is called DocumentListener and contains
the insertUpdate , removeUpdate ,and changeUpdate methods.
￿ s = s.trim();
Removes leading and trailing spaces from the string s .
JTextArea a = new JTextArea(20,30);
Creates a text area with 30 lines. Every
line has 20 characters.
￿ String s = a.getText();
Gets the text from the text area.
Sets the text of the text area.
a.setText("new text");
Adds the text area to the panel. Scroll
bars will appear around the text area when the text becomes too big to fit inside.
p.add(new JScrollPane(textArea));
￿ JComboBox fontComboBox = new JComboBox(fontNames);
Creates a new combo
box. The variable fontNames is the area of strings that will be displayed in the combo
String s = (String)fontComboBox.getSelectedItem();
Retrieves the selected
item from the combo box as String .
￿ fontComboBox.setEditable(false);
Makes the combo box not editable.
Adds an action listener to the combo box.
When the value of the combo box is changed, the actionPerformed method of the a
object will be called.
￿ JCheckBox jb = new JCheckBox("Bold");
Creates a check box with label Bold .
Returns true if the check box is selected.
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