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On December 07 2016 02:20 travis wrote:
So, the semester is coming to an end.
I am gonna need to come up with a project. Learning a new language, going through some book (hopefully interesting), or building something...
Any suggestions for someone that really only knows Java? Something that might look good on a resume for internships?
Read https://mitpress.mit.edu/sicp/full-text/book/book.html.
Btw, the idea that education should focus on tools is 100% ridiculous to me. When I was hired for my current job (enterprise .Net stuff in the insurance biz) I had not written a single line of C#. IMHO, education should be for demonstrating that you are able to learn new things quickly.
And if your place is too lenient with bad coding practise, it is a sure sign to find something better. In a productive environment, a bright new graduate should be brought up to speed fairly quickly, through pairing and code reviews.
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On December 07 2016 03:49 tofucake wrote:
pshhh
even on windows I use shell. cygwin master race
sh? Please tell me you don't use sh... bash is defo the best shell.
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On December 06 2016 19:56 spinesheath wrote:
There's a difference between teaching CS and teaching how to build an OS/DB/Compiler. Those are "how do I connect a kitchen sink" and "how do I install a bath tub". It's a pointless exercise to anyone who is interested in the actual science part, and the wrong focus for anyone interested in becoming a software developer.
The stuff I can get behind for a CS degree is all the math. That's great stuff. The semi-practical stuff that teaches little more than how to be a bad programmer and about as much knowledge about a DB as you can gather in 5 minutes from wikipedia - not so much.
But they dont teach us how to build an OS. It is our exercise to build the OS. They teach us how an OS works and functions and expect us to learn how to build that OS by ourself. They teach the theoretical background and we are expected to work out the practical details after being given the theory.
Same with the DBMS stuff. They teach us all the different approaches that can be done, all the historical stuff that had happened but didnt work, and all the exotic techniques that are currently being tested but not yet established. Then we are asked to implement one ourself and we can choose how we want to do it. The newer, better algorithms that perhaps are more complicated to do right? Or perhaps the tried and true old stuff that may be a little bit slower. The result is not that important but rather how we got there.
I actually really like that approach. I think its the right thing to do. We learn the theory, we are forced to learn the practical stuff, and we can brag with the "interesting" things we have created.
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Hyrule19174 Posts
On December 07 2016 04:09 Acrofales wrote:Show nested quote +On December 07 2016 03:49 tofucake wrote:
pshhh
even on windows I use shell. cygwin master race sh? Please tell me you don't use sh... bash is defo the best shell.
yeah, but I was talking more about (generic shell) vs (windows batch)
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On December 07 2016 04:21 RoomOfMush wrote:Show nested quote +On December 06 2016 19:56 spinesheath wrote:
There's a difference between teaching CS and teaching how to build an OS/DB/Compiler. Those are "how do I connect a kitchen sink" and "how do I install a bath tub". It's a pointless exercise to anyone who is interested in the actual science part, and the wrong focus for anyone interested in becoming a software developer.
The stuff I can get behind for a CS degree is all the math. That's great stuff. The semi-practical stuff that teaches little more than how to be a bad programmer and about as much knowledge about a DB as you can gather in 5 minutes from wikipedia - not so much. But they dont teach us how to build an OS. It is our exercise to build the OS. They teach us how an OS works and functions and expect us to learn how to build that OS by ourself. They teach the theoretical background and we are expected to work out the practical details after being given the theory. Same with the DBMS stuff. They teach us all the different approaches that can be done, all the historical stuff that had happened but didnt work, and all the exotic techniques that are currently being tested but not yet established. Then we are asked to implement one ourself and we can choose how we want to do it. The newer, better algorithms that perhaps are more complicated to do right? Or perhaps the tried and true old stuff that may be a little bit slower. The result is not that important but rather how we got there. I actually really like that approach. I think its the right thing to do. We learn the theory, we are forced to learn the practical stuff, and we can brag with the "interesting" things we have created.
Obviously the details will differ from university to university. But from my experience, it's more like "to install a kitchen sink, you can either use these items like that, or these other items that other way", and then they don't even mention that it's important to know how to use your tools (programming). It's stuff that I can look up on wikipedia in no time, with no scientific value.
Take the compiler example: From a scientific perspective, a compiler is just a function that takes some data a (source coude) and returns some data b (binary). Nothing of value here unless you go into implementation details. You might use the common stuff like a lexer, parser, tokenizer, what have you. But then that's still just a composition of simple functions. You learn how to compose functions in math classes. What you should learn in the more practical classes - if you have any - is how to do that property.
Also, if you use programming as a tool, you should have a very good understanding of it, just like any other tool. That should at least be made clear.
Anyways, I personally had to take a bunch of courses that I felt were neither abstract enough to provide konwledge that could be applied to other stuff, nor concrete enough to be of any practical use. It was a waste of time. Might be different elsewhere.
Ok, enough ranting on that topic from me.
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In my personal opinion CS is a useless degree, just like economy. If you need the maths and theory, you'll be better off just studying maths. If you want to learn programming, well, there's no real university course that will teach you how to do that.
Before you ask why the economy analogy: I've got a friend who finished economy and maths with flying colors and worked for some really big companies that have to do with stocks and what not. What he told me is that if you want to do something relevant economy-wise then no one will hire you after economy. People after maths will be much better with all the mathematical stuff needed while people after humanities will be much better with people skills, that's why big companies hire them and then send them to specific economy courses so they can brush up on their lingo and other skills as necessary.
I think that CS is facing pretty much the same problem. By doing some theory and some practice you don't really get enough of both. You can alleviate some of that by getting hired as a programmer early enough during your studies, but then you're still better off with going pure maths. Likewise, if you want to do pure theoretical stuff you should too just get a degree in mathematics and learn just enough programming (and/or some computer theory) in your free time or from extracurricular courses.
TL;DR: CS, just like economy is not focused enough to give you any real advantage when it comes down to doing anything past the most basic stuff.
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I don't think all of my uni courses were useless with regards to practical programming, particularly the introductory courses and the object oriented course. But they certainly didn't really enforce clean coding practices, nor teach about source control for the vast majority of them, and didn't do any kind of TDD or testing generally beyond "does it work on the assignment test cases the professor uses". All of that I've either picked up at my job or in my free time out of my own interest.
Pure maths wouldn't be that useful IMO for preparing for a programming job.
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On December 07 2016 02:20 travis wrote:
So, the semester is coming to an end.
I am gonna need to come up with a project. Learning a new language, going through some book (hopefully interesting), or building something...
Any suggestions for someone that really only knows Java? Something that might look good on a resume for internships?
The SC2 Map Analyser needs an update, if you want to practice your C.
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On December 07 2016 07:31 Manit0u wrote:
In my personal opinion CS is a useless degree, just like economy. If you need the maths and theory, you'll be better off just studying maths. If you want to learn programming, well, there's no real university course that will teach you how to do that.
Before you ask why the economy analogy: I've got a friend who finished economy and maths with flying colors and worked for some really big companies that have to do with stocks and what not. What he told me is that if you want to do something relevant economy-wise then no one will hire you after economy. People after maths will be much better with all the mathematical stuff needed while people after humanities will be much better with people skills, that's why big companies hire them and then send them to specific economy courses so they can brush up on their lingo and other skills as necessary.
I think that CS is facing pretty much the same problem. By doing some theory and some practice you don't really get enough of both. You can alleviate some of that by getting hired as a programmer early enough during your studies, but then you're still better off with going pure maths. Likewise, if you want to do pure theoretical stuff you should too just get a degree in mathematics and learn just enough programming (and/or some computer theory) in your free time or from extracurricular courses.
TL;DR: CS, just like economy is not focused enough to give you any real advantage when it comes down to doing anything past the most basic stuff.
CS is far from useless, but don't make the mistake of thinking that CS is Software Engineering. I suppose CS is very heavy on the maths and logic of computing in theory, which is relevant to certain applications, but not general programming. For example, if you're doing scientific computing and you need to get the most calculations out of your cpu cycles, then you want to apply CS to find algorithms that will crunch your matrices. Another example is cryptography, which relies heavily on CS to ensure that their methods are secure.
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As someone who is pursuing a C.S. degree, what I am learning (in my major) sure does not feel useless. I suppose I could have learned all of this on my own, but that could be said for literally any degree.
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On December 07 2016 10:38 travis wrote:
As someone who is pursuing a C.S. degree, what I am learning (in my major) sure does not feel useless. I suppose I could have learned all of this on my own, but that could be said for literally any degree.
Yeah this is really it. Also you get a piece of paper saying you can do certain things.
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travis has it.
Also then there's the (probably unfortunate) reality that entry level jobs at some of the highest paying gigs' interviews are heavily biased towards recent cs graduates. (It's getting better, but slowly)
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I have an assignment to make a phone book in java. I can do that but I can't do it according to the requirements in the assignment. I assume I am making an elementary mistake. I'll post one of the sections I get stuck at implementing.
I seem to have some mistake in my put code that then chains to the rest and creates havoc. I have no idea what I am doing wrong though.
At the top I have
private Map<String, LinkedList<String>> phoneBook;
public MapPhoneBook() {
phoneBook = new HashMap<String, LinkedList<String>>();
}
The put itself:
/**
* Associates the specified number with the specified
* name in this phone book.
* post: If the specified name is not present in this phone book,
* the specified name is added and associated with
* the specified number. Otherwise the specified
* number is added to the set of number associated with name.
* @param name The name for which a phone number is to be added
* @param number The number associated with the specified name
* @return true if the specified name and number was inserted
*/
@Override
public boolean put(String name, String number) {
if(phoneBook.containsKey(name)) {
LinkedList<String> numbers = phoneBook.get(name);
if(!numbers.contains(number)) {
numbers.add(number);
return true;
}
} else {
LinkedList<String> numbers = new LinkedList<String>();
numbers.add(number);
phoneBook.put(name, numbers);
return true;
}
return false;
}
Tried the following to see the results:
public class Testphoneb {
public static void main(String[] args) {
Map<String, String> pb = new TreeMap<String, String>();
System.out.println("Size: " + pb.size());
pb.put("a", "1");
pb.put("a", "2");
pb.put("a", "3");
pb.put("b", "2");
System.out.println("Size: " + pb.size());
System.out.println("Get a: " + pb.get("a"));
}
}
When using debug in eclipse with a stop before put b, 2. I find size 1 and a, 3 values as the only thing in the memory section. When I thought it would be 1,2,3.
Edit, old post.
+ Show Spoiler +/**
* Retrieves a set of phone numbers for the specified name. If the
* specified name is not present in this phone book an empty set is
* returned.
* @param name The name whose associated phone numbers are to be returned
* @return The phone numbers associated with the specified name
*/
Set<String> findNumbers(String name); My attempt that returns the following error: java.lang.ClassCastException: java.util.LinkedList cannot be cast to java.util.Set public Set<String> findNumbers(String name) {
Set<String> number = new HashSet<String>();
number = (Set<String>) phoneBook.get(name);
return number;
}I defined phonebook as private Map<String, LinkedList<String>> phoneBook;
phoneBook = new HashMap<String, LinkedList<String>>(); It also fails the required testcode when filled with 3 numbers connected to name a. So I think I have a mistake in my put section that makes one name, multiple numbers replace instead of add. private void fill() {
pb.put("a", "1");
pb.put("c", "3");
pb.put("b", "2");
pb.put("a", "2");
pb.put("b", "1");
pb.put("a", "3");
pb.put("c", "2");
pb.put("aaa", "111");
}assertEquals("Wrong size for number set to a:", 3, pb.findNumbers("a").size());If not required to use a set (which is the area I think I don't understand) it would be something like public List<String> findNumber(String name) {
if(phoneBook.containsKey(name)) {
return phoneBook.get(name);
}
return new LinkedList<String>();
}Can anybody provide some hints on how I should use set to get it working here? This is just one of 4 places using set in this assignment, so an exact solution would not solve the entire homework but help me with understanding how sets work.
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United Kingdom14103 Posts
during my degree we've covered a range of languages (c, java, haskell, prolog, lisp family etc.) , how the hardware behind works, stuff on networking and software engineering methods (plus group projects where weve produced software based off initial requirements given to us).
i probably could have learned java, python or something on my own but not the skills and knowledge surrounding the languages
theres also the maths stuff on algorithms etc. for more background knowledge and my final year courses where ive been able to choose specific areas to pursue further (cryptography, parallel computing, compilers, advanced graphics) which has been interesting so far
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Why did you decide to use a LinkedList? A LinkedList is not a set so you either need to get the LinkedList and then convert it to a Set or change your Map to have a different type of data in it. The latter makes more sense to me, but it might not work everywhere in your assignment. LinkedList should basically never be used in java; I'm pretty sure ArrayList is implemented in a way that makes it strictly better. If you're casting something in java you should double check to make sure you're not doing something wrong typically. There are exceptions, but if your classes are set up properly then you should almost never need to.
You also have confusion with what a Map is I think. The Map is a key:value pairing. If you put the same value into the Map three times you'll just change the value it is paired with. That's why the size of your map is one. You've put the a:1 pair into the map and then changed it to a:2 and then changed it to a:3. Instead you need to see if that value is in the map already. If it is then you need to get that data structure (you're using a LinkedList right now) and add the new value to the List.
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On December 07 2016 22:59 Blitzkrieg0 wrote:
Why did you decide to use a LinkedList? A LinkedList is not a set so you either need to get the LinkedList and then convert it to a Set or change your Map to have a different type of data in it. The latter makes more sense to me, but it might not work everywhere in your assignment. LinkedList should basically never be used in java; I'm pretty sure ArrayList is implemented in a way that makes it strictly better. If you're casting something in java you should double check to make sure you're not doing something wrong typically. There are exceptions, but if your classes are set up properly then you should almost never need to.
You also have confusion with what a Map is I think. The Map is a key:value pairing. If you put the same value into the Map three times you'll just change the value. Instead you need to see if that value is in the map already. If it is then you need to get your storage (you're using a LinkedList right now) and add the new value to the List.
Thank you. I'll try using an arraylist instead, there is no specific reason for using a linkedlist, just first thing I though of. So I should be finding the arraylist in question and inputting a value in it. You are right in the value being replaced which is my problem.
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On December 07 2016 23:03 Yurie wrote:Show nested quote +On December 07 2016 22:59 Blitzkrieg0 wrote:
Why did you decide to use a LinkedList? A LinkedList is not a set so you either need to get the LinkedList and then convert it to a Set or change your Map to have a different type of data in it. The latter makes more sense to me, but it might not work everywhere in your assignment. LinkedList should basically never be used in java; I'm pretty sure ArrayList is implemented in a way that makes it strictly better. If you're casting something in java you should double check to make sure you're not doing something wrong typically. There are exceptions, but if your classes are set up properly then you should almost never need to.
You also have confusion with what a Map is I think. The Map is a key:value pairing. If you put the same value into the Map three times you'll just change the value. Instead you need to see if that value is in the map already. If it is then you need to get your storage (you're using a LinkedList right now) and add the new value to the List. Thank you. I'll try using an arraylist instead, there is no specific reason for using a linkedlist, just first thing I though of. So I should be finding the arraylist in question and inputting a value in it. You are right in the value being replaced which is my problem.
Keep in mind that the ArrayList isn't a Set either so you'll still need to do some conversion.
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Unless you have a very specific reason to use LinkedList, an arraylist is always better. But given that you want numbers to be unique, why not use a HashSet (which will give you most of the functionality you want)?
That said, it should affect performance, and not functionality, because you already test whether the element is present when you insert.
However, I don't quite understand your debugging info. Your phonebook having size one before you add b seems correct: it has one entry: <a, LinkedList object>. Your linked list should have 3 values (1, 2, 3), not your map.
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On December 07 2016 23:18 Acrofales wrote:Unless you have a very specific reason to use LinkedList, an arraylist is always better. But given that you want numbers to be unique, why not use a HashSet (which will give you most of the functionality you want)? That said, it should affect performance, and not functionality. However, I don't quite understand your debugging info. Your phonebook having size one before you add b seems correct: it has one entry: <a, LinkedList object>. Your linked list should have 3 values (1, 2, 3), not your map.
So nested HashSets instead of using a string, arraylist (or linkedlist)? I am not sure how that works but it might be easier since I am required to export it to a set. Else I assume I would have to do something like the following but with the size of the arraylist.
try {
for(int i = 0; i < size-1; i++) {
set.add(count[i]);
}
As for adding the numbers one by one I found the following on stackexchange that I will experiment a bit with:
String key = "mango";
int number = 42;
if (map.get(key) == null) {
map.put(key, new ArrayList<Integer>());
}
map.get(key).add(number);
I only get the last value 3 when I actually check the memory in the variables. So regardless that my code should return 2 it doesn't have the right thing in memory since my put code is wrong.
Edit, thanks for the replies people. I'll try working at it a bit before asking for help again.  Great advice.
Edit 2, tasted nested hashmaps and it seems a bad idea since I need double strings in the nested one and only have one input remaining, the phone number.
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On December 07 2016 23:26 Yurie wrote:+ Show Spoiler +On December 07 2016 23:18 Acrofales wrote:Unless you have a very specific reason to use LinkedList, an arraylist is always better. But given that you want numbers to be unique, why not use a HashSet (which will give you most of the functionality you want)? That said, it should affect performance, and not functionality. However, I don't quite understand your debugging info. Your phonebook having size one before you add b seems correct: it has one entry: <a, LinkedList object>. Your linked list should have 3 values (1, 2, 3), not your map. So nested HashSets instead of using a string, arraylist (or linkedlist)? I am not sure how that works but it might be easier since I am required to export it to a set. Else I assume I would have to do something like the following but with the size of the arraylist. try {
for(int i = 0; i < size-1; i++) {
set.add(count[i] ;
}
As for adding the numbers one by one I found the following on stackexchange that I will experiment a bit with: String key = "mango";
int number = 42;
if (map.get(key) == null) {
map.put(key, new ArrayList<Integer>());
}
map.get(key).add(number); I only get the last value 3 when I actually check the memory in the variables. So regardless that my code should return 2 it doesn't have the right thing in memory since my put code is wrong. Edit, thanks for the replies people. I'll try working at it a bit before asking for help again. Great advice.
Sets are the smarter way to do it. A Set is just a List that can't have duplicate values. Having a duplicate phone number does not make sense. I was under the impression that you had to use a List for the assignment, but if you can choose then do use a Set instead of an ArrayList.
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EPT
