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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

Answer 3

Question 4

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

Answer 4

Question 5

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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Source:  OpenStax, Object-oriented programming (oop) with java. OpenStax CNX. Jun 29, 2016 Download for free at https://legacy.cnx.org/content/col11441/1.201
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