Java quiz series

[Uriah]

I apologize. I forgot to say that I dont have the next quiz if it's correct. Great question, by the way, Deque. Im learning a lot from these

[Deque]

What  happens here?

Code: [Select]

for (byte b = Byte.MIN_VALUE; b < Byte.MAX_VALUE; b++) {
   if (b == 0x90) {
      System.out.print("Joy!");
   }
}

[vezzy]

You're looping for the minimum and maximum value of a byte as defined by Java's Byte class and printing text in the event of an Intel NOP instruction. This does not occur and hence nothing is printed.

[Deque]

You're looping for the minimum and maximum value of a byte as defined by Java's Byte class and printing text in the event of an Intel NOP instruction. This does not occur and hence nothing is printed.

Yeah, but why does it not occur?

[vezzy]

Hmmm.

Well, 0x90 in decimal is equal to 144, so that's outside of the byte range (up to 127).

Thus I'm assuming this is an actually integer, and to get this to work you'll either need to cast 0x90 to byte or convert the byte to an integer.

[Deque]

Hmmm.

Well, 0x90 in decimal is equal to 144, so that's outside of the byte range (up to 127).

Thus I'm assuming this is an actually integer, and to get this to work you'll either need to cast 0x90 to byte or convert the byte to an integer.

Your explanation is correct, do you have the next quiz?
(Sorry for editing your post. I pressed the wrong button while trying to quote you, but I didn't change anything)

[vezzy]

Pass the quiz on to the next person.

[Deque]

The next one is not a program, but a question.

What is the magic number of a .class file and where did it come from?

[Uriah]

The magic number is a hex number meant to identify the file format. It is 0xCAFEBABE.

Came from a combination of eating at a cafe and a band who used to play there (grateful dead) and a friend dying there. Not sure whether it was the band or the actual death but then the founder of java and friends started calling the place cafe dead. james gosling realized CAFEDEAD was a hex number and started using it for the persistent object format. Deciding on cafe as a theme, he grepped for characters that made sense with it and got CAFEBABE.


Dont have next quiz if im correct, and nice question

[Deque]

The magic number is a hex number meant to identify the file format. It is 0xCAFEBABE.

Came from a combination of eating at a cafe and a band who used to play there (grateful dead) and a friend dying there. Not sure whether it was the band or the actual death but then the founder of java and friends started calling the place cafe dead. james gosling realized CAFEDEAD was a hex number and started using it for the persistent object format. Deciding on cafe as a theme, he grepped for characters that made sense with it and got CAFEBABE.


Dont have next quiz if im correct, and nice question

You are correct.
Does anybody else have a quiz? You are free to go.

[Matriplex]

Sure

Let's say you have the following class Man:

Code: [Select]

    public class Man implements java.io.Serializable {
        public String name;
        public String number;
        public transient int age;
        public boolean male;
    }

And the following PersonInLog class:

Code: [Select]

    public class PersonInLog {
        public static void main(String[] args) {
            Man e = new Man();
            e.name = "Bill";
            e.number = "555-555-5555";
            e.age = 30;
            e.male = true;
            try {
                FileOutputStream personFile = new FileOutputStream("/tmp/bill.ser");
                ObjectOutputStream out = new ObjectOutputStream(personFile);
                out.writeObject(e);
                out.close();
                personFile.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

And finally this:

Code: [Select]

import java.io.*;
public class PersonOutLog {

        public static void main(String[] args) {
            Man e = null;
            try {
                FileInputStream personFile = new FileInputStream("/tmp/bill.ser");
                ObjectInputStream in = new ObjectInputStream(personFile);
                e = (Man) in.readObject();
                in.close();
                personFile.close();
            } catch (IOException e) {
                return;
            } catch (ClassNotFoundException c) {
                return;
            }
            System.out.println("Name: " + e.name);
            System.out.println("Number: " + e.number);
            System.out.println("Age: "  + e.age);
            System.out.println("Male: " + e.male);
        }
    }

What will be printed?

Edit:
100 posts!
Also, just to clear it up this is a trick question in a way. Just throwin that out there.

Edit 2:
Excuse me for all the mistakes this is pseudo code written while half asleep. I think I've fixed most of them by now though.

[Lac]

Name: Bill
Number: 555-555-5555
Age: 30
Male: true


If you were to attempt to read the Man object using your PersonOutLog class, then the above would be printed.

[Matriplex]

Excuse me I forgot I posted this, I was going to revise it the next day..

This is a completely unfair question, I don't tell you what class I'm running or in which order. If I said you run PersonInLog and the PersonOutLog, then yes you would be correct.

Forgive me, I wasn't thinking when I wrote this. Consider Lac correct

[Lac]

  Yeah that's why I made sure to say IF you try to call the Man object.

[Psycho_Coder]

So what's the next question ? Or has the previous question been accepted as complete.