| << Chapter < Page | Chapter >> Page > |
| Figure 7 - Question 9. |
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This is a title |
True or False: The code shown in Listing 7 will compile and run successfully producing the output shown in Figure 8 .
| Listing 7 - Question 10. |
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/*File Q10.java
************************************************/import java.awt.*;
import javax.swing.*;/*Note the following inheritance hierarchy
java.lang.Objectjava.awt.Component
java.awt.Containerjava.awt.Window
java.awt.Framejavax.swing.JFrame
*/public class Q10{
public static void main(String[]args){
JFrame aFrame = new JFrame("This is a title");System.out.println(aFrame.getTitle());
Foo aFoo = new Foo();aFoo.runIt(aFrame);
}//end main}//end class Q10
//=============================================//class Foo{
public<T extends Object>void runIt(T ref){
System.out.println("Running runIt");System.out.println(ref.getTitle());
}//end runIt}//end Foo
//=============================================// |
| Figure 8 - Question 10. |
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This is a title |
What is the meaning of the following two images?
These images were inserted here simply to insert some space between the questions and the answers to keep them from being visible on the screen at thesame time.
This image was also inserted for the purpose of inserting space between the questions and the answers.
False. This is an unsuccessful call to generic method with specified upper-bound of Object. The incoming reference is received as type Object and must be downcast to at leastFrame to call the method named getTitle. The incoming parameter is received as the type ofthe specified upper-bound. This results in the compiler error shown in Figure 9 .
| Figure 9 - Answer 10. |
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Q10.java:36: error: cannot find symbol
System.out.println(ref.getTitle());^
symbol: method getTitle()location: variable ref of type T
where T is a type-variable:T extends Object declared in method<T>runIt(T)
1 error |
False. This is an unsuccessful call to generic method with default upper- bound of Object. The incoming reference is received as type Object and must bedowncast to at least Frame to call the method named getTitle. The incoming parameter is received as the type of the specified upper-bound which is Objectby default. This results in the compiler error shown in Figure 10 .
| Figure 10 - Answer 9. |
|---|
Q09.java:36: error: cannot find symbol
System.out.println(ref.getTitle());^
symbol: method getTitle()location: variable ref of type T
where T is a type-variable:T extends Object declared in method<T>runIt(T)
1 error |
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