| << Chapter < Page | Chapter >> Page > |
| Listing 7 - Question 13. |
|---|
/*File Q13.java
************************************************/import java.util.*;
public class Q13{ArrayList<Integer>var1 = new ArrayList<Integer>();void runIt(){var1.add(new Integer(1));
var1.add(new Integer(2));var1.add(new Integer(3));//Get an iterator
Iterator iter = var1.iterator();//Perform the iterationwhile(iter.hasNext()){
System.out.println(iter.next().intValue());}//end while loop}//end runItpublic static void main(String[] args){new Q13().runIt();
}//end main}//end class Q13//=============================================// |
| Figure 5 - Question 13. |
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1
23 |
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 program produces the error shown in Figure 6 below. You must qualify the iterator as shown in Listing 8 to correct the error. If you don't qualify the iterator, the reference is retrieved fromthe list as type Object. The Object class neither defines nor inherits a method named intValue.
| Listing 8 - Answer 13. |
|---|
/*File A13.java
************************************************/import java.util.*;
public class A13{ArrayList<Integer>var1 = new ArrayList<Integer>();void runIt(){var1.add(new Integer(1));
var1.add(new Integer(2));var1.add(new Integer(3));//Get an iterator
Iterator<Integer>iter = var1.iterator();//Perform the iteration
while(iter.hasNext()){System.out.println(iter.next().intValue());
}//end while loop}//end runItpublic static void main(String[]args){
new Q13().runIt();}//end main
}//end class A13//=============================================// |
| Figure 6 - Answer 13. |
|---|
Q13.java:22: error: cannot find symbol
System.out.println(iter.next().intValue());^
symbol: method intValue()location: class Object
1 error |
False. This program produces the compiler error shown in Figure 7 below. This is the result of attempting to store an object's reference of type String in acollection reserved exclusively for references to objects of type Date.
| Figure 7 - Answer 12. |
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Q12.java:13: error: no suitable method found for add(String)
var1.add("abcd");^
method ArrayList.add(int,Date) is not applicable(actual and formal argument lists differ in length)
method ArrayList.add(Date) is not applicable(actual argument String cannot be converted to Date by method invocation
conversion)1 error |
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