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| Figure 3 - Question 3. |
|---|
class java.awt.Button
Button01class java.awt.Button
Button02class java.awt.Label
Label01class java.awt.Label
Label02 |
True or False: The code shown in Listing 4 will compile and run successfully producing the output shown in Figure 4 .
Listing 4 - Question 4.
/*File Q04.java
************************************************/import java.util.ArrayList;
import java.awt.Button;import java.awt.Label;
import java.awt.Component;public class Q04{
/*Given:
Button and Label are subclasses of the Componentclass.
The getClass method is defined in the Objectclass. When called on a reference to an object,
the method returns the name of the class fromwhich the object was instantiated.
*/public static void main(String[] args){//Create and populate a list designed to
// store references to objects of type Button// and display its contents.
ArrayList<Button>listA = new ArrayList<>();
listA.add(new Button("Button01"));listA.add(new Button("Button02"));
display(listA);System.out.println("");//blank line
//Create and populate a list designed to// store references to objects of type Label
// and display its contents.ArrayList<Label>listB = new ArrayList<>();
listB.add(new Label("Label01"));listB.add(new Label("Label02"));
display(listB);}//end main
//-------------------------------------------//static void display(ArrayList<Object>list){
for(Object n : list){System.out.println(n.getClass());
if(n instanceof Button){System.out.println(
((Button)n).getLabel());}else if(n instanceof Label) {
System.out.println(((Label)n).getText());}//end else
}//end for loop}//end display
}//end class Q04 | Figure 4 - Question 4. |
|---|
class java.awt.Button
Button01class java.awt.Button
Button02class java.awt.Label
Label01class java.awt.Label
Label02 |
True or False: The code shown in Listing 5 will compile and run successfully producing the output shown in Figure 5 .
Listing 5 - Question 5.
/*File Q05.java
************************************************/import java.util.ArrayList;
import java.awt.Window;import java.awt.Frame;
import javax.swing.JFrame;public class Q05{
/*Given:
Component extends ObjectContainer extends Component
Window extends ContainerFrame extends Window
JFrame extends FrameThe getClass method is defined in the Object
class. When called on a reference to an object,the method returns the name of the class from
which the object was instantiated.*/
public static void main(String[]args){
Frame frame0 = new Frame("Frame0");ArrayList<Frame>listA = new ArrayList<>();
listA.add(frame0);listA.add(new Frame("Frame1"));
display(listA);ArrayList<Window>listB = new ArrayList<>();
listB.add(new Window(frame0));listB.add(new Window(frame0));
display(listB);ArrayList<JFrame>listC = new ArrayList<>();
listC.add(new JFrame("JFrame0"));listC.add(new JFrame("JFrame1"));
display(listC);}//end main
//-------------------------------------------//static void display(
ArrayList<? super JFrame>list){
for(Object n : list){System.out.println(n.getClass());
}//end for loopSystem.out.println();//blank line
}//end display}//end class Q05 
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