Java AWT Choice

by

Java AWT (Abstract Window Toolkit) Choice is a class in the Java programming language that provides a compact menu of choices. It is used to create a drop-down list of items from which the user can choose one item.

Here is an example of how to create a Choice in Java AWT:

import java.awt.Choice;
import java.awt.Frame;

public class MyFrame extends Frame {

    public MyFrame() {
        // Create a new Choice
        Choice choice = new Choice();

        // Add some items to the Choice
        choice.add("Item 1");
        choice.add("Item 2");
        choice.add("Item 3");

        // Add the Choice to the Frame
        add(choice);

        // Set the properties of the Frame
        setTitle("Java AWT Choice Example");
        setSize(300, 200);
        setVisible(true);
    }

    public static void main(String[] args) {
        new MyFrame();
    }
}

In the example above, we create a new Choice, add some items to it, and then add the Choice to a Frame. When we run the program, we will see a Frame with a drop-down list containing the three items we added to the Choice. When the user selects an item from the list, we can use the getSelectedItem() method of the Choice class to get the selected item.

AWT Choice Class Declaration:

The AWT Choice class is declared as follows:

public class Choice extends Component implements ItemSelectable, Accessible

The Choice class extends the Component class and implements two interfaces – ItemSelectable and Accessible.

Here is a brief explanation of each of these:

  • Component: This is the base class for all AWT components. It provides methods for managing the size, position, and visibility of the component.
  • ItemSelectable: This interface is used to indicate that an object can be selected. The Choice class implements this interface to allow items in the list to be selected.
  • Accessible: This interface is used to provide accessibility information for a component. The Choice class implements this interface to allow assistive technologies to interact with the component.

Choice Class constructor:

The Choice class in AWT provides a default constructor that can be used to create a new Choice object. The syntax for the constructor is as follows:

public Choice()

This constructor creates a new Choice object with an empty list of items.

Here’s an example of how to create a new Choice object using the default constructor:

Choice choice = new Choice();

This will create a new Choice object called choice. The list of items in the choice will be empty until items are added using the add() method.

Alternatively, the Choice class also provides a constructor that allows you to initialize the list of items when creating the Choice object. The syntax for this constructor is as follows:

public Choice(String[] items)

Here, the items parameter is an array of String objects that will be added to the choice. For example:

String[] choices = {"Red", "Green", "Blue"};
Choice colorChoice = new Choice(choices);

This will create a new Choice object called colorChoice with three items – “Red”, “Green”, and “Blue”.

Methods inherited by class:

The Choice class in AWT inherits several methods from its superclass, Component. Here are some of the commonly used inherited methods:

  • void setFont(Font font): Sets the font used to display the text in the Choice component.
  • void setSize(int width, int height): Sets the size of the Choice component.
  • void setLocation(int x, int y): Sets the location of the Choice component.
  • void setVisible(boolean visible): Sets the visibility of the Choice component.

In addition to the inherited methods, the Choice class also provides its own set of methods for managing the list of items in the Choice component. Here are some of the commonly used methods:

  • void add(String item): Adds an item to the list of choices in the Choice component.
  • void add(String item, int index): Adds an item to the list of choices in the Choice component at a specified index.
  • void remove(String item): Removes an item from the list of choices in the Choice component.
  • int getItemCount(): Returns the number of items in the list of choices in the Choice component.
  • String getItem(int index): Returns the item at the specified index in the list of choices in the Choice component.
  • String getSelectedItem(): Returns the currently selected item in the list of choices in the Choice component.

These methods allow you to add and remove items from the list of choices in the Choice component, as well as retrieve information about the items in the list and the currently selected item.

Choice Class Methods:

The Choice class in AWT provides several methods to manage the list of items in the choice component. Here are some of the commonly used methods:

  • void add(String item): Adds an item to the end of the list of choices in the Choice component.
  • void add(String item, int index): Inserts an item into the list of choices at the specified index.
  • void remove(String item): Removes the specified item from the list of choices in the Choice component.
  • void removeAll(): Removes all items from the list of choices in the Choice component.
  • int getItemCount(): Returns the number of items in the list of choices in the Choice component.
  • String getItem(int index): Returns the item at the specified index in the list of choices in the Choice component.
  • int getSelectedIndex(): Returns the index of the currently selected item in the list of choices in the Choice component.
  • String getSelectedItem(): Returns the currently selected item in the list of choices in the Choice component.
  • void select(int index): Selects the item at the specified index in the list of choices in the Choice component.
  • void select(String item): Selects the specified item in the list of choices in the Choice component.

These methods allow you to add and remove items from the list of choices in the Choice component, retrieve information about the items in the list and the currently selected item, and select a particular item in the list.

Java AWT Choice Example:

Here is an example of how to use the Choice class in Java AWT:

import java.awt.Choice;
import java.awt.Frame;
import java.awt.Label;
import java.awt.event.ItemEvent;
import java.awt.event.ItemListener;

public class ChoiceExample extends Frame implements ItemListener {
    
    private Choice colorChoice;
    private Label label;
    
    public ChoiceExample() {
        setTitle("Choice Example");
        
        // Create a Choice component
        colorChoice = new Choice();
        colorChoice.add("Red");
        colorChoice.add("Green");
        colorChoice.add("Blue");
        colorChoice.addItemListener(this);
        
        // Create a Label component
        label = new Label("Choose a color:");
        
        // Add components to the frame
        add(label);
        add(colorChoice);
        
        // Set the size and visibility of the frame
        setSize(200, 100);
        setVisible(true);
    }
    
    public void itemStateChanged(ItemEvent e) {
        // Get the selected item from the Choice component
        String color = colorChoice.getSelectedItem();
        
        // Update the Label component with the selected color
        label.setText("You chose " + color);
    }
    
    public static void main(String[] args) {
        ChoiceExample example = new ChoiceExample();
    }
}

In this example, we create a new ChoiceExample class that extends the Frame class and implements the ItemListener interface. We create a Choice component called colorChoice with three items – “Red”, “Green”, and “Blue”. We add an ItemListener to the colorChoice component so that we can detect when the user selects a new color. We also create a Label component called label with some initial text.

In the itemStateChanged() method, we get the currently selected item from the colorChoice component and update the text of the label component to display the selected color.

Finally, we create an instance of the ChoiceExample class and set its size and visibility. When the user selects a new color from the colorChoice component, the text of the label component will update to display the selected color.

Java AWT Choice Example with ActionListener:

Here is an example of how to use the Choice class in Java AWT with an ActionListener:

import java.awt.Choice;
import java.awt.Frame;
import java.awt.Label;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

public class ChoiceExample implements ActionListener {
    
    private Frame frame;
    private Choice colorChoice;
    private Label label;
    
    public ChoiceExample() {
        frame = new Frame("Choice Example");
        
        // Create a Choice component
        colorChoice = new Choice();
        colorChoice.add("Red");
        colorChoice.add("Green");
        colorChoice.add("Blue");
        colorChoice.addActionListener(this);
        
        // Create a Label component
        label = new Label("Choose a color:");
        
        // Add components to the frame
        frame.add(label);
        frame.add(colorChoice);
        
        // Set the size and visibility of the frame
        frame.setSize(200, 100);
        frame.setVisible(true);
    }
    
    public void actionPerformed(ActionEvent e) {
        // Get the selected item from the Choice component
        String color = colorChoice.getSelectedItem();
        
        // Update the Label component with the selected color
        label.setText("You chose " + color);
    }
    
    public static void main(String[] args) {
        ChoiceExample example = new ChoiceExample();
    }
}

In this example, we create a new ChoiceExample class that uses an ActionListener instead of an ItemListener. We create a Frame object called frame, a Choice object called colorChoice, and a Label object called label. We add the colorChoice and label components to the frame.

In the constructor, we add an ActionListener to the colorChoice component. When the user selects a new color, the actionPerformed() method is called. In this method, we get the currently selected item from the colorChoice component and update the text of the label component to display the selected color.

Finally, we create an instance of the ChoiceExample class and set the size and visibility of the frame. When the user selects a new color from the colorChoice component, the text of the label component will update to display the selected color.