Java AWT Chapter 1

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Questions and Answers

What does the TextField class primarily implement?

A complex text formatting tool

A character display area

A multi-line text entry area

A single-line text entry area (correct)

Which constructor initializes a text field with a specified string and width?

TextField(String str)

TextField()

TextField(int numChars)

TextField(String str, int numChars) (correct)

What method is used to obtain the current text contained in a TextField?

setEchoChar()

getText() (correct)

echoCharIsSet()

setText()

Which method allows you to set a character that will be echoed in the TextField?

setEchoChar() Signup and view all the answers

What is the purpose of the echoCharIsSet() method in the TextField class?

To determine if an echo character has been set Signup and view all the answers

What is the purpose of the AWT in Java?

To develop GUI or window-based applications. Signup and view all the answers

Which of the following is NOT a type of container in AWT?

Button Signup and view all the answers

Which layout manager is used by default in a Window class?

BorderLayout Signup and view all the answers

What method is used to add a control component to a window in AWT?

add() Signup and view all the answers

Which of the following components is NOT a subclass of Component in AWT?

Window Signup and view all the answers

What distinguishes a Frame from a Dialog in the AWT class hierarchy?

Dialog has borders and a title. Signup and view all the answers

What functionality does an Applet provide in AWT?

Can be embedded into a web page. Signup and view all the answers

To what class does the method add() belong in AWT?

Container Signup and view all the answers

What is the purpose of the getLabel( ) method in the Button class?

To obtain the label of the button Signup and view all the answers

Which statement is true regarding the initial state of a Checkbox created using Checkbox() constructor?

The label is blank and the checkbox is unchecked Signup and view all the answers

What does the setState(boolean on) method do in the Checkbox class?

It sets the checkbox state based on the boolean value Signup and view all the answers

What is the correct syntax to create a Checkbox that is initially checked?

Checkbox c3=new Checkbox("Option", true); Signup and view all the answers

Which method is used to set the label of a Button in Java?

setLabel(String str) Signup and view all the answers

In which scenario would you use a CheckboxGroup?

To group checkboxes where only one can be selected at a time Signup and view all the answers

Which option correctly describes the behavior of a checkbox?

Clicking toggles its state between checked and unchecked Signup and view all the answers

What color is set as the background in the provided Button class applet?

Red Signup and view all the answers

What is the primary difference between the first and second constructors of GridLayout?

The first constructor does not specify rows and columns, while the second does. Signup and view all the answers

How many buttons are added in the GridLayout example using the first constructor?

5 Signup and view all the answers

What is the main purpose of the setLayout method in the Applet class?

To define the layout manager for the applet. Signup and view all the answers

What additional parameters does the third constructor of GridLayout take compared to the first?

Horizontal and vertical gaps. Signup and view all the answers

What is the result of using the constructor Frame() without arguments?

A standard window without a title. Signup and view all the answers

What method is used to set the size of a frame in pixels?

setSize(int newWidth, int newHeight) Signup and view all the answers

What is the purpose of the `setEchoChar('*')` method in the TextField?

It specifies the character displayed instead of the real input. Signup and view all the answers

Which title setting method is specific to Frame class?

setTitle(String str) Signup and view all the answers

Which constructor of TextArea allows for initial text input?

TextArea(String str) Signup and view all the answers

In the context of GridLayout, what does the '2' signify in GridLayout(2,3)?

The number of rows in which components will be arranged. Signup and view all the answers

In the context of TextField, what does the parameter passed to its constructor specify?

The maximum number of characters. Signup and view all the answers

Which method is unique to the TextArea class as opposed to TextField?

append(String str) Signup and view all the answers

What does the `numLines` parameter in the TextArea constructor control?

Height of the TextArea in lines. Signup and view all the answers

Which of the following options is NOT a valid scroll bar constant for TextArea?

SCROLLBARS_HORIZONTAL Signup and view all the answers

Which layout manager is used in the provided init() method of the first text field program?

FlowLayout Signup and view all the answers

What will happen when a single character is typed in the TextField with setEchoChar('*') set?

The asterisk will replace the typed character in the display. Signup and view all the answers

Study Notes

Introduction to AWT

AWT (Abstract Window Toolkit) is an API for developing GUI (Graphical User Interface) applications in Java.
Components in AWT are platform-dependent, meaning they adapt to the display characteristics of the operating system.
GUI design in Java is facilitated through pre-defined classes in the java.awt package.

AWT Class Hierarchy

AWT employs a class hierarchy consisting of Component and Container.
Components: Include elements such as buttons, text fields, and scrollbars.
Containers: Hold components and types include Window, Frame, Dialog, and Panel.
Window: Lacks borders and a title, uses BorderLayout by default.
Frame: A subclass of Window, includes a title bar, menu bar, and supports resizing.
Dialog: Features borders and a title, used for pop-up messages.
Applet: Java program running within a web browser, embedded in an HTML page using the APPLET tag.

AWT Controls

AWT supports various controls including:
- Labels
- TextField
- TextArea
- Buttons
- Checkboxes
- Choice
- Lists
- Menus

Adding Controls

Controls are added to a window using the add() method defined in Container.
Syntax for adding: Component add(Component compObj)

Button Class

The Button class methods include:
- setLabel(String str): Sets the button label.
- getLabel(): Retrieves the current label.

Checkbox

A Checkbox is used for binary options (on/off) and features a label for clarity.
Checkbox constructors:
- Checkbox(): Creates an unchecked checkbox without a label.
- Checkbox(String str): Creates an unchecked checkbox with a specified label.
- Checkbox(String str, boolean on): Initializes a checkbox with a specified label and state.

Methods of Checkbox

boolean getState(): Retrieves the current state of the checkbox.
void setState(boolean on): Sets the state of the checkbox.

TextField

The TextField class serves as a single-line text-entry area for user input.
Constructors include:
- TextField(): Creates a default text field.
- TextField(int numChars): Creates a text field of specified width.
- TextField(String str): Initializes with a defined string.

Methods of TextField

String getText(): Retrieves the text contained in the field.
void setText(String str): Updates the text field with a new string.
void setEchoChar(char ch): Displays a specific character instead of typed characters.

TextArea

TextArea is a multiline editor for extended text input.
Constructors allow setting dimensions and initial text.
Methods include:
- void append(String str): Adds specified string to the existing text.

Grid Layout

Utilizes a grid layout manager for arranging components in a grid form.
Constructors enable specifying rows and columns of components along with gaps.

Frame Class

Frame is a subclass of Window that includes title and menu bars, borders, and resizing capabilities.
Constructors initialize frames with or without titles.
Methods include:
- void setSize(int newWidth, int newHeight): Sets the frame size in pixels.
- void setTitle(String str): Updates the frame's title.

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Description

Explore the fundamentals of Java's Abstract Window Toolkit (AWT) in this quiz. Understand key concepts and components essential for developing GUI applications using Java. This chapter covers the basics and the class hierarchy involved in Java AWT.