Jude Niroshan

What can I make the signature other than Object... so that it takes Objects or Functionals without casting?

No, it is not possible. The reason is you can not have a single Java interface that represents all Functionals(aka Lambda expressions) in Java.

Hi Paul,

I have used Enthuware mock exam bundle to obtain my OCA & OCP in java 8.  
I'm looking forward to renew my certificate to Java 21.
I strongly believe your book has everything that I've missed so far.
All the best!  

Hi Ken,

I have been working with Java for around 5 years so far. I saw how the language has changed to catch up with newest programming language trends and enhance the power of Java itself. They even changed their lease cycles which they thought to be a solution to hook up the existing language users. But I think Kotlin has geared up with most up-to-date tools within the language core itself. My question is, does your book covers how I can start thinking of using Kotlin to my existing projects? Because I know some big companies have already started to adapt to Kotlin but they have started with their Unit tests. I would like to know is this aspect has been covered in your book. I think it's a very practical usage to try out any new language(JVM languages) for an existing project.  

Best regards,
Jude

Campbell Ritchie's answer is correct. I'll explain a bit if you still didn't understand.

Books [] myBooks = new Books [3];

In the above line, it means, you created an Array which can hold 3 Books. That's all what this line means.

But you assume, the array do actually have 3 Books when you write that above line. This is wrong!

So, you must fill that empty myBooks array with Books objects

Welcome to Coderanch!  

I would happy to see where do you define the variable Path

Please note that when you are writing quality code, you should always follow the coding standards. In Java you should always start a variable with a lowercase letter and follow the camelCase style when you are giving names to variables and methods. I hope you will provide the Path variable definition and where it is done.

I think what you should do is, you should try to build a project with what you know. Then think whether were you lacking some knowledge which was essential and you couldn't really understood. Then take a while to think whether you are going to take a certification or just Googled it and learn by applying those.

As Roel said, put it as Oracle Certified Associate, Java SE 8 Programmer . That sounds associate as well as Programmer.  

Howdy everyone,

I was playing around with new Java 8 streams API, when I caught up with this compilation error. (I'm using IntelliJ IDEA)

Below is my Student.java

public class Student {    private String name;    private int marks;    private int age;    private List<String> fluentAreas = new ArrayList<>();    //getters & setters        public Student(String name, int marks) {        this.name = name;        this.marks = marks;    }    @Override    public String toString() {        return name + ':' + marks ;    } }

Here is my method method class:

public class Main {    static Set<String> namesPool = new HashSet<>();    static UnaryOperator<Student> giveMarks = student -> {student.setMarks(ThreadLocalRandom.current().nextInt());        return student;};    static UnaryOperator<Student> calcAge = student -> {student.setAge(22); return student;};    static {        namesPool.add("Shawn");        namesPool.add("Shenal");        namesPool.add("Jude");        namesPool.add("Nipuni");        namesPool.add("Ellie");        namesPool.add("Rosa");        namesPool.add("Miftha");        namesPool.add("Roshan");        namesPool.add("Hasantha");    }    public static void main(String[] args) throws IOException {        List<Student> studentList = getCollegeClass();        Map<String,List<? super  Student>> passedStudents =  studentList.stream()                                                         .map(e->customizeStudent(calcAge,e))                                                         .map(e->customizeStudent(giveMarks,e))                                                         .filter(e->e.getMarks()>65)                                                         .collect(Collectors.groupingBy(Student::getName));    }    private static List<Student> getCollegeClass(){        ExecutorService service = Executors.newCachedThreadPool();        List<Student> students = new ArrayList<>();        namesPool.forEach(n->service.submit(()->students.add(new Student(n,(int)(Math.random()*100)))));        return  students;    }    private static Student customizeStudent(UnaryOperator<Student> studentUnaryOperator, Student student){        return studentUnaryOperator.apply(student);    } }

This is the compilation error that I received,

Error:(36, 66) java: incompatible types: inference variable R has incompatible bounds
   equality constraints: java.util.Map<java.lang.String,java.util.List<org.chapter3.Student>>
   upper bounds: java.util.Map<java.lang.String,java.util.List<? super org.chapter3.Student>>,java.lang.Object

Thanks & Regards,
Jude

Hi Theo,

Appreciate your reply.  I understood how the parallel reductions happens. You have pointed some important facts about reduce().

reduce() has 3 versions. But the most complicated one is 3 argument version which accept:

Identity U

accumulator BiFunction<U, ? super T, U>

combiner BinaryOperator<U>

Most important fact that I learnt was, even though accumulators may run in parallel, combiners will always run sequentially which they were appeared to be in the List.

Indeed an interactive environment. You gotta check it out.

Go to https://sybextestbanks.wiley.com/ and select the OCP book. Then you will get a prompt to register. When you click next you will be asked a random question from the book. Once you done with it, you will receive an unique ID  to the given email address. By using that ID, you can simply login to that and enjoy!

Hope this helps!

Hi,

I have the paper book version of Oracle Certified Professional Java SE 8 Programmer II Study Guide. The book says it includes a access for an interactive learning environment. But in order to access those content I have to enter a unique PIN. I couldn't find anywhere in this book.

Where is that unique PIN appears in the paper book?

Regards,
Jude

Hi Jeanne,

Always I'm pleased to see your responses. I have just bought it (directly from PearsonVue). Actually I was able to have the discount. It costs only $97.50. Thanks alot

Regards,
Jude

I have a doubt whether this 35% discount is only offered for upgrade exams. But I don't have any certifications other than OCAJP Java 8. Here is a screenshot of those confused items when I go to buy voucher in Oracle university.



Does regular OCPJP Java 8 doesn't have any discount applicable? Should I need to buy the second one shown in the image?

Dear Ranchers,

I am going to schedule my OCP Java 8 exam. (1Z0-809) I saw that in oracle official website, they are having a promotion for many certification exams up-to 35% off including the exam that I am going to take. I actually did this when I was doing my OCA java 8. But I'm sorry to ask this again, cos it's bit confusing and I have forgot how this process works.

What I need to know is how to get this promotion? I have tried to book the exam through PearsonVue website (after logging into my account). Actually, I couldn't find anywhere that they mention about promotion codes or something like that. I went up to scheduling the exam on a date in their wizard (in PearsonVue), but there were nothing about the promotion. Can anyone who had done it in recently or anyone who knows how this works, can you please reply to this post, mentioning the step by step that I need to follow?  

I hope this post may be helpful in future for someone who is going to schedule an oracle exam online.

Thanks & Regards,
Jude

Hi everyone,

I am preparing for my OCP Java SE 8. So far, I have done 2 enthuware mock exams and I got failed those both. I'm kind of disparate now. (Cos I was working with Java almost 3 years now. But I couldn't pass this mock exams at least getting 65%)

Can anyone teach me about the reduce() in case of a parallelSteam()

Below caption is taken from Oracle docs.

The identity value must be an identity for the accumulator function. This means that for all t, accumulator.apply(identity, t) is equal to t. The accumulator function must be an associative function.

I can't understand what this means> "that for all t, accumulator.apply(identity, t) is equal to t."

I don't know how the parallel streams process each element in reduce(). Can someone help me?

Regards,
Jude