The Big Programming Thread - Page 815

On December 13 2016 23:02 tofucake wrote:
Usually homework programs like that have a UI supplied by the professor/TAs exactly so that automated tests can be written, and the assignment is to make all of the programmatic logic.

On December 14 2016 07:42 enigmaticcam wrote:
.NET question. I have a client program that copies a file to a server via windows UNC, e.g. \\servername\directory. Sometimes the file is very large. I'd like to be able to zip it first, send to server, and unzip on server. Is there any way to do this? I can't see that it can be done without having some type of service on the server to do it. I figured you can't, that any zipping/unzipping function would have to be performed on the client, but thought I'd ask just in case.

On December 14 2016 02:32 phar wrote:
Was there a given lower level non GUI interface that you had to implement? Or does your prof just hate your TAs?

On December 13 2016 16:48 3FFA wrote:
What are some good Discord IRC chat groups for helping learn? Asking for both myself and others, since a chat community is helpful for both answering questions as well as morale, preventing burnout.

On December 15 2016 04:32 Morfildur wrote:
On the topic of Java. Does anyone have experience with any HMVC web frameworks? I really dislike MVC since I've learned how HMVC works, but all the web frameworks in java seem to be purely MVC based or do HMVC terribly. I've adapted Spring to do HMVC with a few ugly workarounds and replacing it's whole routing, so at least that works, but I'd rather have something that does it out of the box.

On December 15 2016 09:42 travis wrote:
It's that time. That time where my final exam is tomorrow.

And therefore I flood the forum with review questions. Let's start with this one.

(all questions pertain to java if they require code)

"What technique is used (instead of looping) to create a server that can efficiently handle
numerous clients?"

I have no idea. sockets? threads?

On December 15 2016 09:47 Birdie wrote:

Sounds to me like it's asking for threads, looping means everyone basically just joins a queue and you loop through their requests one by one which is horrible compared to threads. If a server has a thread for each client it is far more efficient than any loop-based method.

On December 15 2016 09:42 travis wrote:
It's that time. That time where my final exam is tomorrow.

And therefore I flood the forum with review questions. Let's start with this one.

(all questions pertain to java if they require code)

"What technique is used (instead of looping) to create a server that can efficiently handle
numerous clients?"

I have no idea. sockets? threads?

On December 15 2016 09:47 Birdie wrote:

Sounds to me like it's asking for threads, looping means everyone basically just joins a queue and you loop through their requests one by one which is horrible compared to threads. If a server has a thread for each client it is far more efficient than any loop-based method.

On December 15 2016 23:46 travis wrote:
"when does a non-static initialiation block run"

On December 15 2016 23:46 travis wrote:
Okay now let's go over typecasting. I had so much trouble on this on the first exam, it confuses me so badly.
Let's look at it's example, where Fish extends Lifeform, and that Plant also extends Lifeform.

Fish fish = new Fish();
Lifeform life = new Lifeform();
Lifeform x = new Fish();

So what do you call each part of this line
Is it "Type variablename = new object from class" ?

Ok anyways let's move onto the questions. Each one you have to answer "won't compile", "throws exception" or "works fine"

1. Plant a = x; //x is a fish, no relation to plants, I say this won't compile
2. Plant b = (Plant) x; //x is a fish, I put it won't compile on the exam and missed it. correct answer is it throws exception because It compiles because of the cast to plant?
3. Lifeform c = fish; //I put this works fine on exam and got it. So, you can downcast fine when instantiating?
4. Fish d = (Fish) life; //I put throws exception.. I got that right. This doesn't work? then what is the point of casting?
5. Fish e = (Fish) x; // Oh I guess this is the point of casting. For when the object was typed as the super but an instantiation of the subclass. so this works?
6. Plant p = (Plant) fish //I think this doesn't compile because fish is of type fish which is unrelated to plant

On December 15 2016 23:46 travis wrote:
Now it says "assume there is a methhod called move in the Lifeform class that has been overridden in the Plant class."

Lifeform x = new Plant();
x.move();

Which version of the move will run.
Lifeform version, or Plant version

I put lifeform version and missed it. So the rule is what? That the version of the method that is ran is based on the object that was instantiated and not the type it was cast to? But that's the opposite for when you want to look at it's field values, right?

On December 15 2016 23:46 travis wrote:
Now it has the question

public void foo(Lifeform x) {...}

Which of these could you pass in as a parameter
1.) Fish
2.) Plant
3.) Lifeform
4.) Object

I put 1, 2, 3 and got it right. So you can only pass in the class and subclasses? What if I tried to put in a subclass of Fish as a parameter. Would it work?

On December 15 2016 23:46 travis wrote:
Okay now it says we have an arraylist "list" of type LifeForm. Fish have a method called swim.
using a for each loop, call the swim method on all the fish. Do I do this(i missed this on the exam so I am unsure):

for((Fish fish : list) {
fish.swim();
}

so yeah I missed this. They tell me to do "instanceof cast". Where am I doing an instanceof cast? Also they crossed out my "Fish" after the for. What is the correct structure for this? Is it

for(Lifeform fish : list) {
if(instanceOf(fish)) {
fish.swim();
} }

for (Lifeform lifeform : list) {
    if (Lifeform instanceof Fish {
        lifeform.swim();
}

On December 16 2016 00:09 travis wrote:
sorry, I meant when are static initialization blocks ran

so the answer is "when the class is first loaded"
But... what does that actually mean? When are classes loaded?

On December 15 2016 23:46 travis wrote:
ok its the morning of. time for question flood

here is a few i missed on my first exam

"when does a non-static initialiation block run"

I answered:

before anything else, including the main method

I got this wrong. When I do a google search on this, I find many different answers. So what is accurate?

public class Foo {
   int bar = 5;

   public Foo() {
     bar = 3;
   }

Okay now let's go over typecasting. I had so much trouble on this on the first exam, it confuses me so badly.
Let's look at it's example, where Fish extends Lifeform, and that Plant also extends Lifeform.

Fish fish = new Fish();
Lifeform life = new Lifeform();
Lifeform x = new Fish();

So what do you call each part of this line
Is it "Type variablename = new object from class" ?

Ok anyways let's move onto the questions. Each one you have to answer "won't compile", "throws exception" or "works fine"

1. Plant a = x; //x is a fish, no relation to plants, I say this won't compile
2. Plant b = (Plant) x; //x is a fish, I put it won't compile on the exam and missed it. correct answer is it throws exception because It compiles because of the cast to plant?

3. Lifeform c = fish; //I put this works fine on exam and got it. So, you can downcast fine when instantiating?

4. Fish d = (Fish) life; //I put throws exception.. I got that right. This doesn't work? then what is the point of casting?
5. Fish e = (Fish) x; // Oh I guess this is the point of casting. For when the object was typed as the super but an instantiation of the subclass. so this works?

6. Plant p = (Plant) fish //I think this doesn't compile because fish is of type fish which is unrelated to plant

Now it says "assume there is a methhod called move in the Lifeform class that has been overridden in the Plant class."

Lifeform x = new Plant();
x.move();

Which version of the move will run.
Lifeform version, or Plant version

I put lifeform version and missed it. So the rule is what? That the version of the method that is ran is based on the object that was instantiated and not the type it was cast to? But that's the opposite for when you want to look at it's field values, right?

Now it has the question

public void foo(Lifeform x) {...}

Which of these could you pass in as a parameter
1.) Fish
2.) Plant
3.) Lifeform
4.) Object

I put 1, 2, 3 and got it right. So you can only pass in the class and subclasses? What if I tried to put in a subclass of Fish as a parameter. Would it work?

public void foo(Object o)

Okay now it says we have an arraylist "list" of type LifeForm. Fish have a method called swim.
using a for each loop, call the swim method on all the fish. Do I do this(i missed this on the exam so I am unsure):

for((Fish fish : list) {
fish.swim();
}

so yeah I missed this. They tell me to do "instanceof cast". Where am I doing an instanceof cast? Also they crossed out my "Fish" after the for. What is the correct structure for this? Is it

for(Lifeform fish : list) {
if(instanceOf(fish)) {
fish.swim();
} }

for(Lifeform lf : list) {
  if(lf instanceof Fish) {
     ((Fish) lf).swim(); //first cast to Fish, then call swim.
  }
}

thanks... that's all my questions from exam 1