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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.
True.
True. Every new class inherits a default version of the equals method from the class named Object. Therefore, a new class that implements the Comparator interface already has such a method. The new class is free to override the inherited version, or to simply make use of the inherited version.
True.
False. When the fillIt method shown in Listing 1 returns, the collection object referred to by ref will contain references to four objects of type MyClass with those objects encapsulating the values 4, 3, 2, and 1 with no duplicates.
False. In Listing 1 , the constructor that is called to instantiate a new TreeSet object receives an incoming parameter of type Comparator . Once again, don't confuse the two interfaces simply because they have similar names.
False. It is possible to instantiate a new TreeSet object using a constructor that receives an incoming reference to a Comparator object, in which case it is not necessary for the objects in the collection to implementthe Comparable interface. Don't confuse the two interfaces.
1234
False. Although the name of the Comparable interface is similar to the name of the Comparator interface, they are different interfaces. Don't be confused by the similarity of the names.
True.
True.
False. The sorting order established by a Comparator may be different or may be the same as the natural order.
| Listing 1 . Comparator02.java. |
|---|
//File Comparator02.java
//Copyright 2001, R.G.Baldwinimport java.util.*;
import java.io.Serializable;public class Comparator02{
public static void main(String args[]){
new Worker().doIt();}//end main()
}//end class Comparator02class Worker{
public void doIt(){Iterator iter;
Collection ref;ref = new TreeSet(new TheComparator());
Populator.fillIt(ref);iter = ref.iterator();
while(iter.hasNext()){System.out.print(iter.next());
}//end while loopSystem.out.println();
}//end doIt()}// end class Worker
class Populator{public static void fillIt(Collection ref){
ref.add(new MyClass(4));ref.add(new MyClass(4));
ref.add(new MyClass(3));ref.add(new MyClass(2));
ref.add(new MyClass(1));}//end fillIt()
}//end class Populatorclass MyClass{
int data;MyClass(){
data = 0;}//end noarg constructor
MyClass(int data){this.data = data;
}//end parameterized constructorpublic String toString(){
return "" + data;}//end overridden toString()
}//end MyClassclass TheComparator
implements Comparator,Serializable{public int compare(Object o1,Object o2){
if(!(o1 instanceof MyClass))throw new ClassCastException();
if(!(o2 instanceof MyClass))throw new ClassCastException();
if(((MyClass)o1).data<((MyClass)o2).data)
return -1;if(((MyClass)o1).data>((MyClass)o2).data)
return 1;else return 0;
}//end compare()public boolean equals(Object o){
if(!(o instanceof TheComparator))return false;
else return true;}//end overridden equals()
}//end class TheComparator |
This section contains a variety of miscellaneous information.
Financial : Although the Connexions site makes it possible for you to download aPDF file for this module at no charge, and also makes it possible for you to purchase a pre-printed version of the PDF file, youshould be aware that some of the HTML elements in this module may not translate well into PDF.
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In the past, unknown individuals have copied my modules from cnx.org, converted them to Kindle books, and placed them for sale onAmazon.com showing me as the author. I neither receive compensation for those sales nor do I know who does receive compensation. If youpurchase such a book, please be aware that it is a copy of a module that is freely available on cnx.org and that it was made andpublished without my prior knowledge.
Affiliation : I am a professor of Computer Information Technology at Austin Community College in Austin, TX.
-end-
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