Unit 4 java programming ii 21 collected by bipin

Unit-4/ Java Programming-II
21
Collected by Bipin Timalsina

Unit-4/ Java Programming-II
22
Collected by Bipin Timalsina
Checkbox Group
It is possible to create a set of mutually exclusive check boxes in which one and only one check
box in the group can be checked at any one time. These check boxes are often called radio
buttons, because they act like the station selector on a car radio — only one station can be
selected at any one time. For creating a set of mutually exclusive check boxes, we must first
define the group to which they will belong and then specify that group when we construct the
check boxes. Check box groups are objects of type CheckBoxGroup . Only the default
constructor is defined, which creates an empty group.
We can determine which check box in a group is currently selected by calling
getSelectedCheckbox( ). We can set a check box by calling setSelectedCheckbox( ). These
methods are as follows:
Checkbox getSelectedCheckbox( )
void setSelectedCheckbox(Checkbox wh)
Here, wh is the check box that we want to be selected. The previously selected check box will be
turned off.
Example: CheckBoxGroup
package awtexample;
import java.awt.*;
public class CheckBoxGroupExample
{
CheckBoxGroupExample(){
Frame f= new Frame("CheckboxGroup Example");
Label l1 = new Label("Choose your Faculty");
l1.setBounds(100,50,200,20);
CheckboxGroup cbg = new CheckboxGroup();
Checkbox checkBox1 = new Checkbox("BIM", cbg, true);
checkBox1.setBounds(100,100, 50,50);
Checkbox checkBox2 = new Checkbox("BSc.CSIT", cbg, false);
checkBox2.setBounds(100,200, 100,50);
Checkbox checkBox3 = new Checkbox("BCA", cbg, false);
checkBox3.setBounds(100,300, 50,50);
f.add(l1);

Unit-4/ Java Programming-II
23
Collected by Bipin Timalsina
f.add(checkBox1); f.add(checkBox2); f.add(checkBox3);
f.setSize(500,500);
f.setLayout(null);
f.setVisible(true);
}
public static void main(String args[]) {
new CheckBoxGroupExample();
}
}

Unit-4/ Java Programming-II
24
Collected by Bipin Timalsina
Choice Controls
The Choice class is used to create a pop -up list of items from which the user may choose. Thus,
a Choice control is a form of menu. When inactive, a Choice component takes up only enough
space to show the currently selected item. When the user clicks on it, the whole list of choices
pops up, and a new selection can be made. Each item in the list is a string that appears as a left
justified label in the order it is added to the Choice object.
 Choice only defines the default constructor, which creates an empty list.
 In order to add a selection to the list, add( ) is used. It has this general form:
void add(String name)
Here, name is the name of the item being added. Items are added to the list in the order in
which calls to add( ) occur.
 In order to determine which item is currently selected, we may call either any of the
following methods:
String getSelectedItem( )
int getSelectedIndex( )
 The getSelectedItem( ) method returns a string containing the name of the item.