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Sybex 816 Java OCP 11 Programmer II Study Guide

 
Greenhorn
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Java OCP 11 Programmer II Study Guide

145 page

2:  public class UseTreeSet {
3:     static class Rabbit{ int id; }
4:     public static void main(String[] args) {
5:        Set<Duck> ducks = new TreeSet<>();
6:        ducks.add(new Duck("Puddles"));
7:
8:        Set<Rabbit> rabbits = new TreeSet<>();
9:        rabbits.add(new Rabbit());  // ClassCastException
10: } }
Line 6 is fine. Duck does implement Comparable. TreeSet is able to sort it into the proper position in the set. Line 9 is a problem. When TreeSet tries to sort it, Java discovers the fact that Rabbit does not implement Comparable. Java throws an exception that looks like this:

Exception in thread "main" java.lang.ClassCastException:
  class Duck cannot be cast to class java.lang.Comparable

class Duck cannot be cast to class java.lang.Comparable -----
 
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Welcome to the Ranch
I presume that is the book by Boyarsky and Selikoff? Please look here, where I can't find what you showed. Pleas wait for Jeanne to see this thread; it would appear you have found a new erratum.
 
Vladimir Prud
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Hello, yes, this is a book by Scott Selikoff and Jeanne Boyarsky,
but the title of OCP Oracle Certified Professional Java SE 11 Programmer II Study Guide: Exam 1Z0-816 and Exam 1Z0-817
I bought it at https://www.wiley.com



I am reading a book on vitalsource, perhaps the page numbers are not quite correct there. an example is located in chapter 3, just above the topic "Working with Generics"
 
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It's on page 147 in the printed book, so pretty close.

Definitely should be Rabbit, not Duck. I've added it to the errata. Quack!
 
Vladimir Prud
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Hello,I found another typo, 436 page,8 chapter

Manipulating Input Streams
All input stream classes include the following methods to manipulate the order in which data is read from a stream:

// InputStream and Reader
public boolean markSupported()
public void void mark(int readLimit)

public void reset() throws IOException

public long skip(long n) throws IOException

 
Campbell Ritchie
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I presume you have checked the errata because that does look like an error. You can't usually use the same keyword twice.
 
Jeanne Boyarsky
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Confirmed and added to the errata. Thanks for noticing!
 
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