Transcript Even-Driven Programming and basic Graphical User Interface

Even-Driven Programming and
basic Graphical User Interface
Exam 2 – Section 02
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Section 02
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Exam 2 – Section 01
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Avg: 128.8 (85%)
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Exam 2
1. In String class, substring() is a(n)
Attribute
Method
Statement
Criteria
Exam 2
2. The following statement:
double[] studentGPA = new double[12];
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only declares the array studentGPA and did not
allocate memory for this array
only allocates memory for this array studentGPA
and did not declare it
creates 12 studentGPA objects
declares the array named studentGPA and
allocates memory for this array
Exam 2
3. Suppose an array contains 1024 elements.
What are the least and the greatest number
of comparisons for a successful search
using linear search?
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1 and 10
1 and 1024
1 and 8
1 and 1023
Exam 2
4. Suppose a sorted array contains 1024
elements. What are the least and the
greatest number of comparisons for a
successful search using binary search?
1 and 1024
1 and 10
1 and 8
1 and 9
Exam 2
5. Which of the followings is the constructor of
the class MyString?
public String MyString (String str) {…..}
public MyString(String str) { ….}
public void MyString(String str) {….}
public Boolean MyString(String str) {….}
Exam 2
6. The amount of memory allocated to store an
array depends on:
a. the name of the array
b. the size of the array
c. the size and type of values in the array
d. none of the above
Exam 2
6. The amount of memory allocated to store an
array depends on:
a. the name of the array
b. the size of the array
c. the size and type of values in the array
d. none of the above
Exam 2
7. How many comparisons we need to perform
to find x=10 from the following array with 9
elements using binary search
-100 -80 -20 -10 0 10 20 80 100
a. 1
Pass 1: (0+8)/2 = 4.
0<10
Pass 2: (5+8)/2 = 6.
20>10
b. 2
Pass 3: (5+5)/2 = 5
10=10
c. 3
d. 4
Exam 2
8. Array is a collection of data values of the
different data types
True
False
Exam 2
8. Array is a collection of data values of the
different data types
True
False
Exam 2
9. This is a special method that is invoked
when a new object of a class is created:
a. Main method
b. Constructor
c. New method
d. Void method
Exam 2
10. In order to run a Java program, this
program must include at least one class that
has main method
a. True
b. False
Exam 2
B
A
D
C
Exam 2
E
OR
C
C
OR
E
D
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Or
B
Or
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Exam 2
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E
=
B
D
C
Exam 2
C
B
D
A
D
A
Exam 2
public String ExampleClass(String anExample) {
example = new String(anExample);
}
Constructor doesn’t have a return data type
Exam 2
public class QuestionOne {
private double c;
public QuestionOne() {
c=0;
}
private void methodOne (int a) {
c=a;
}
public double methodTwo() {
return c;
}
}
public class QuestionOneMain {
public static void main(String args[]) {
QuestionOne q1;
q1 = new QuestionOne();
q1.c = 12;
q1.methodOne( 12);
double result = q1.methodTwo();
}
}
C is a private data member and thus can not be assessed outside of QuestionOne
Class
methodOne is also a private method
Exam 2
17.
obj = new QuestionTwo(); //count = 0
obj.modifyCount(); // count = (0+10)*2 = 20
obj.printCount();
count=20
Exam 2
18.
String resultStr = q3.getSubMessage(16,22);
// resultStr = “Easter”
System.out.println("A part of this message is "+
resultStr+" length="+resultStr.length());
resultStr = “Easter” and length=6
What is Graphical User Interface (GUI)
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A graphical user interface is a method of
interacting with a computer through a
metaphor of direct manipulation of graphical
images and widgets in addition to text.
GUI display visual elements such as icons,
windows, menu, buttons, checkboxes…
Examples
Examples
GUI in Java
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Java.AWT package:
GUI objects are implemented by using native GUI
objects and may behave differently on different OSs.
Javax.swing package (only available from JDK 1.2
onward):
GUI objects are implemented fully in Java and
therefore behave the same on different OSs.
Offers new features compared to Java.AWT package
Event-driven programming
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An event occurs when the user interacts with
a GUI object (click a button, move a mouse,
press a key…)
Plan for this week
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Create a frame
Create a button and handling button event
Create a frame
Code
import javax.swing.*;
Import GUI swing
package
public class JFrameSubclass extends JFrame {
private static final int FRAME_WIDTH=300;
private static final int FRAME_HEIGHT=200;
private static final int FRAME_X_ORIGIN=150;
private static final int FRAME_Y_ORIGIN = 250;
public JFrameSubclass () {
setTitle("My First Subclass");
setSize(FRAME_WIDTH, FRAME_HEIGHT);
setLocation(FRAME_X_ORIGIN,
FRAME_Y_ORIGIN);
setDefaultCloseOperation(EXIT_ON_CLOSE);
}
}
Code
import javax.swing.*;
Create a subclass that
inherits JFrame class
public class JFrameSubclass extends JFrame {
private static final int FRAME_WIDTH=300;
private static final int FRAME_HEIGHT=200;
private static final int FRAME_X_ORIGIN=150;
private static final int FRAME_Y_ORIGIN = 250;
public JFrameSubclass () {
setTitle("My First Subclass");
setSize(FRAME_WIDTH, FRAME_HEIGHT);
setLocation(FRAME_X_ORIGIN,
FRAME_Y_ORIGIN);
setDefaultCloseOperation(EXIT_ON_CLOSE);
}
}
JFrame class
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Type: “JFrame class Java” in Google and
choose the link:
http://java.sun.com/j2se/1.4.2/docs/api/javax/
swing/JFrame.html
Code
import javax.swing.*;
Constant declarations
public class JFrameSubclass extends JFrame {
private static final int FRAME_WIDTH=300;
private static final int FRAME_HEIGHT=200;
private static final int FRAME_X_ORIGIN=150;
private static final int FRAME_Y_ORIGIN = 250;
public JFrameSubclass () {
setTitle("My First Subclass");
setSize(FRAME_WIDTH, FRAME_HEIGHT);
setLocation(FRAME_X_ORIGIN,
FRAME_Y_ORIGIN);
setDefaultCloseOperation(EXIT_ON_CLOSE);
}
}
Code
import javax.swing.*;
Constructor for this
JFrameSubclass class
public class JFrameSubclass extends JFrame {
private static final int FRAME_WIDTH=300;
private static final int FRAME_HEIGHT=200;
private static final int FRAME_X_ORIGIN=150;
private static final int FRAME_Y_ORIGIN = 250;
public JFrameSubclass () {
setTitle("My First Subclass");
setSize(FRAME_WIDTH, FRAME_HEIGHT);
setLocation(FRAME_X_ORIGIN,
FRAME_Y_ORIGIN);
setDefaultCloseOperation(EXIT_ON_CLOSE);
}
}
Using methods from JFrame class
setTitle methods:
Description is available at:
http://java.sun.com/j2se/1.4.2/docs/api/java/awt/Frame.html#set
Title(java.lang.String)
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setTitle
public void setTitle(String title)
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Sets the title for this frame to the specified string.
Example:
setTitle("My First Subclass”);
Using methods in JFrame
setSize(int, int)
Avaiable at:
http://java.sun.com/j2se/1.4.2/docs/api/java/awt/Compo
nent.html#setSize(int,%20int)
public void setSize(int width, int height)
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–
Resizes this component so that it has width width and
height height.
Example:
setSize(FRAME_WIDTH, FRAME_HEIGHT);
Using methods in JFrame
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setLocation
http://java.sun.com/j2se/1.4.2/docs/api/java/awt/Component
.html#setLocation(int,%20int)
public void setLocation(int x, int y)
Moves this component to a new location. The top-left corner of
the new location is specified by the x and y parameters in the
coordinate space of this component's parent.
Example: setLocation(FRAME_X_ORIGIN, FRAME_Y_ORIGIN);
Using methods in JFrame
setDefaultCloseOperation:
http://java.sun.com/j2se/1.4.2/docs/api/javax/swing/JFra
me.html#setDefaultCloseOperation(int)
public void setDefaultCloseOperation(int operation)
Example:
setDefaultCloseOperation(EXIT_ON_CLOSE);
Using public constants in JFrame
EXIT_ON_CLOSE
http://java.sun.com/j2se/1.4.2/docs/api/javax
/swing/JFrame.html#EXIT_ON_CLOSE
 public static final int EXIT_ON_CLOSE
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Create a button
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Create a dumb GUI first
Add a module to handle event later
Create a dumb GUI
Code
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
Packages included for
event and GUI objects
public class JButtonFrame extends JFrame {
private static final int FRAME_WIDTH=300;
private static final int FRAME_HEIGHT=200;
private static final int FRAME_X_ORIGIN=150;
private static final int FRAME_Y_ORIGIN = 250;
private static final int BUTTON_WIDTH=80;
private static final int BUTTON_HEIGHT=30;
private JButton cancelButton;
private JButton okButton;
Code
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class JButtonFrame extends JFrame {
private static final int FRAME_WIDTH=300;
private static final int FRAME_HEIGHT=200;
private static final int FRAME_X_ORIGIN=150;
private static final int FRAME_Y_ORIGIN = 250;
private static final int BUTTON_WIDTH=80;
private static final int BUTTON_HEIGHT=30;
private JButton cancelButton;
private JButton okButton;
Code
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class JButtonFrame extends JFrame {
private static final int FRAME_WIDTH=300;
private static final int FRAME_HEIGHT=200;
private static final int FRAME_X_ORIGIN=150;
private static final int FRAME_Y_ORIGIN = 250;
private static final int BUTTON_WIDTH=80;
private static final int BUTTON_HEIGHT=30;
private JButton cancelButton;
private JButton okButton;
Code
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class JButtonFrame extends JFrame {
private static final int FRAME_WIDTH=300;
private static final int FRAME_HEIGHT=200;
private static final int FRAME_X_ORIGIN=150;
private static final int FRAME_Y_ORIGIN = 250;
private static final int BUTTON_WIDTH=80;
private static final int BUTTON_HEIGHT=30;
private JButton cancelButton;
private JButton okButton;
Constructor for this class
public JButtonFrame () {
Container contentPane= getContentPane();
setTitle("My Button class");
setResizable(false);
setSize(FRAME_WIDTH, FRAME_HEIGHT);
setLocation(FRAME_X_ORIGIN, FRAME_Y_ORIGIN);
contentPane.setLayout(null);
contentPane.setBackground(Color.white);
Constructor for this class
okButton = new JButton("OK");
okButton.setBounds(70,125,BUTTON_WIDTH,BUTTON_HEIGHT);
contentPane.add(okButton);
cancelButton = new JButton("Cancel");
cancelButton.setBounds(160,125,BUTTON_WIDTH,BUTTON_HEIGHT);
contentPane.add(cancelButton);
setDefaultCloseOperation(EXIT_ON_CLOSE);
}
}