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  • Should try...catch go inside or outside a loop?

    - by mmyers
    I have a loop that looks something like this: for(int i = 0; i < max; i++) { String myString = ...; float myNum = Float.parseFloat(myString); myFloats[i] = myNum; } This is the main content of a method whose sole purpose is to return the array of floats. I want this method to return null if there is an error, so I put the loop inside a try...catch block, like this: try { for(int i = 0; i < max; i++) { String myString = ...; float myNum = Float.parseFloat(myString); myFloats[i] = myNum; } } catch (NumberFormatException ex) { return null; } But then I also thought of putting the try...catch block inside the loop, like this: for(int i = 0; i < max; i++) { String myString = ...; try { float myNum = Float.parseFloat(myString); } catch (NumberFormatException ex) { return null; } myFloats[i] = myNum; } So my question is: is there any reason, performance or otherwise, to prefer one over the other? EDIT: The consensus seems to be that it is cleaner to put the loop inside the try/catch, possibly inside its own method. However, there is still debate on which is faster. Can someone test this and come back with a unified answer? (EDIT: did it myself, but voted up Jeffrey and Ray's answers)

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  • what does a tool like Jasper Reports give me?

    - by Itay Moav
    Ok, So I have to generate very complex reports from my DB. If I am to do it with SQL the query themselves will be complex, and I will have to do some more manipulation on the results later, code level. How do libraries like Jasper Reports/ Crystal Reports and friends save me time when developing such reports? What will they give me?

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  • Where is the error in my code?

    - by Lulu Larson
    /** Yields: a String that contains each capital Letter (in 'A'..'Z') whose representation is prime */ public static String primeChars() { String s = ""; // inv: s contains each capital in "A'..c-1 whose representation is prime for (char c = 'A'; c <= 'Z'; c=(char)(c+1)) { if (Loops.isPrime((int)c) == true) { s= s+1; } } // s contains each capital in 'A' ..'Z' whose rep is a prime return s; }

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  • How to clean up my code

    - by simion
    Being new to this i realy am trying to learn how to keep code as simple as possible, whilst doing the job its supposed to. The question i have done is from project eulur, it says Each new term in the Fibonacci sequence is generated by adding the previous two terms. By starting with 1 and 2, the first 10 terms will be: 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, ... Find the sum of all the even-valued terms in the sequence which do not exceed four million. Here is my code below, i was wondering what the best way of simplifying this would be, for a start removing all of the .get(list.length()-1 )..... stuff would be a good start if possible but i dont really no how to? Thanks public long fibb() { ArrayList<Integer> list = new ArrayList<Integer>(); list.add(1); list.add(2); while((list.get(list.size() - 1) + (list.get(list.size() - 2)) < 4000000)){ list.add((list.get(list.size()-1)) + (list.get(list.size() - 2))); } long value = 0; for(int i = 0; i < list.size(); i++){ if(list.get(i) % 2 == 0){ value += list.get(i); } } return value; }

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  • Hibernate Session flush behaviour [ and Spring @Transactional ]

    - by EugeneP
    I use Spring and Hibernate in a web-app, SessionFactory is injected into a DAO bean, and then this DAO is used in a Servlet through webservicecontext. DAO methods are transactional, inside one of the methods I use ... getCurrentSession().save(myObject); One servlet calls this method with an object passed. The update seems to not be flushed at once, it takes about 5 seconds to see the changes in the database. The servlet's method in which that DAO's update method is called, takes a fraction of second to complete. After the @Transactional method of DAO is completed, flushing may NOT happen ? It does not seem to be a rule [ I already see it ]. Then the question is this: what to do to force the session to flush after every DAO method? It may not be a good thing to do, but talking about a Service layer, some methods must end with immediate flush, and Hibernate Session behavior is not predictable. So what to do to guarantee that my @Transactional method persists all the changes after the last line of that method code? getCurrentSession().flush() is the only solution? p.s. I read somewhere that @Transactional IS ASSOCIATED with a DB Transaction. Method returns, transaction must be committed. I do not see this happens.

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  • Collection, which method is used to authorize an add of an element ?

    - by Duke Vador
    We find a lot of concrete subclasses under Collection. While trying to add an element in a concrete collection, this collection will use a method to determine if it can accept to store the element (and eventually that this element is not already in the collection). It could use equals(), hashCode() or compareTo() of the element. Is it possible to find a summary about which method is used by each implementation of Collection ? Thanks a lot for your answers.

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  • Extract elements from list based on object property type

    - by Dustin Digmann
    Often, I have a list of objects. Each object has properties. I want to extract a subset of the list where a specific property has a predefined value. Example: I have a list of User objects. A User has a homeTown. I want to extract all users from my list with "Springfield" as their homeTown. I normally see this accomplished as follows: List users = getTheUsers(); List returnList = new ArrayList(); for (User user: users) { if ("springfield".equalsIgnoreCase(user.getHomeTown()) returnList.add(user); } I am not particularly satisfied with this solution. Yes, it works, but it seems so slow. There must be a non-linear solution. Suggestions?

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  • Matching Class arrays

    - by frinkz
    I'm writing a routine to invoke methods, found by a name and an array of parameter Class values Matching the Method by getName works, but when trying to match the given Class[] for parameters, and Method.getParameterTypes(), I'm having trouble. I assumed that this would work: Class[] searchParams = new Class[] { float.class, String.class }; Class[] methodParams = m.getParameterTypes(); if(methodParams == searchParams) { m.invoke(this, paramValues); } But apparantly not - m.invoke is never reached. I've checked, and methodParams gives the same classes as searchParams. The code below works, and picks the right method, but it seems like a very dirty way of doing things, I'm sure I'm missing something obvious. Class[] searchParams = new Class[] { float.class, String.class }; Class[] methodParams = m.getParameterTypes(); boolean isMatch = true; for(int i = 0; i < searchParams.length; i++) { if(!searchParams.getClass().equals(methodParams.getClass())) { isMatch = false; } } if(isMatch) { m.invoke(this, paramValues); }

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  • How to avoid the linebreak inside a word (Static Layout

    - by Addev
    I'm trying to make a text as big as I can making it fit a Rect. basically I use a StaticLayout for pre-calculate the text size and make it fit the Rect's height: // Since the width is fixed for the StaticLayout it should only fit the height while (currentHeight>Rect.getHeight()){ size-=2; } textPaint.setTextSize(size); The problem is that if the Rect is very high, the exit condition is reached but breaking the words (see the capture). Is there a way for avoid this? Goal: Actual: Current code: textSize=MAX_TEXT_SIZE do { if (textSize < mMinTextSize) { Log.i(TAG, "Min reached"); textSize = mMinTextSize; textPaint.setTextSize(textSize); fits = true; } else { textPaint.setTextSize(textSize); StaticLayout layout = new StaticLayout(text, textPaint, targetWidth, Alignment.ALIGN_NORMAL, 1.0, 0, true); layout.draw(canvas); float heightRatio= (float) layout.getHeight() / (float) targetHeight; boolean fitsHeight = heightRatio<= 1f; if (fitsHeight) { fits = true; } else { textSize -= 2; } } Log.i(TAG, "textSize=" + textSize + " fits=" + fits); } while (!fits); thanks

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  • Full and Partial Matching of Sets

    - by jeffrey
    I have several sets of the same type [Y, M, D] and am trying to write a function to search these sets and return an array of the available sets that fit my parameters. ReturnedSets = return_matches(Y,M,D); I want the three parameters of the function return_matches to be optional. Which means any combination of values can be used to return the sets. For example, one could write - return_matches(13,null,2); - and the function would look for all sets that contain [13, anyValue, 2]; I'm writing this in PHP, to allow users to manage dated files on my website, but I'd like to be able to use this function again for other uses. Thanks! edit: (This, or variations of this, is all I can come up with so far... There is something extra that I don't understand, because this function ends up / would not work to return sets that contain y and d, but leaving m arbitrary. if(y == s[0]){ if(m == s[1]){ if(d == s[2]){ print "day match"; } } else {print "month match";} } else {print "year match";} } else {print "no match";}

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  • Can I write a module/filter that gets fired before the web app get's run in Tomcat?

    - by Blankman
    Can I write a module/filter that gets put into the processing pipleline in Tomcat BEFORE the web application even gets run? Something that I could turn on/off for each web application that tomcat is handling. is this possible? So basically it would be a re-usable filter that hooks into the web pipeline that could alter the requests behavior or perform/modify the requests. One example would be to log all ip's, or redirect based on the url, block the request, etc.

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  • using JDBC with persistence.xml

    - by moshe shamy
    I am building a framework that manage the access to the database. the framework getting tasks from the user and handle a connection pooling that manage the access to the database. the user just send me SQL commands. One of the feature that i would like to support is working with JPA, in this case i will provide entity manager. in some cases i would like to provide JDBC access as well as JPA access. the arguments for the database are written in XML file. so for JPA i need to write the property in persistence.xml so it will be not so smart to write again the same arguments for JDBC. do you know if i can get the arguments of the database from persistence.xml, do you know if there is a source code that do it. or should i parse persistence.xml by myself?

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  • Mysql maven jpa skeleton

    - by coubeatczech
    Hi, is there a skeleton for a project using mysql, some eclipse/top link with RESOURCE_LOCAL as connection type? Preferably using maven. I'm searching for it for hours and can't get running even the sipmlest exaple. So if you had it ready and running, please, post :-). Even something as simple as these two classes only. @Entity public class Message implements Serializable{ public Message() {} public Message(String s){ this.s = s; } @Id String s; public String getS(){ return s; } } public class App { static private EntityManagerFactory emf; static private EntityManager em; public static void main( String[] args ) { emf = Persistence.createEntityManagerFactory("persistence"); em = emf.createEntityManager(); Message m = new Message("abc"); em.persist(m); } }

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  • Help choosing the right data structure

    - by devoured elysium
    I need a data structure with the following requirements: Needs to be able to get elements by index (like a List). I will always just add / remove elements from the end of the structure. I am inclined to use an ArrayList. In this situation, it seems to be O(1) both to read elements (they always are?), remove elements (I only need to remove them at the end of the list) and to add(I only add to the end of the list). There is only the problem that time to time the ArrayList will have a performance penalty when it's completly full and I need to add more elements to it. Is there any other better idea? I don't think of a data structure that'd beat the ArrayList here. Thanks

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  • How to explicitly terminate http connection from server with no response header

    - by Gagandip
    I am developing a server simulator for one of my client application. I am using GlassFish server. I have to simulate a http connection terminate condition in my server application. Is there a way by which I can explicitly terminate a connection from server side such that client does not receive any response header. Currently I have tried many options like closing the response outputStream. But in every case a http 200 OK message is delivered to the client application. I would like to consume the http-request and do not want to return anything to the client. I am using a simple conrtroller servlet and had overridden doGet() and doPost() functions.

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  • Invoking callhierarchy for a method

    - by Steven
    hi, I have an object of type IMethod which represents a method .I want to get the Call Hierarchy of this method . Which methods should i call to get the call hierarchy of a method? Is there any method by which i can do it? I know that i can get it by ctrl+alt+H but i want the code or method for invoking it. Thanks

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  • how do you find the exact variable of a null pointer exception

    - by OVERTONE
    I've been at this one for a bit now. I've got a null pointer exception so im guessing somethings not been initialized. AdminMessages.inbox1.setText(messageRsetArray[0]); thats my code where its targetting. but i cant find what inside it hasnt been initiazed. AdminMessages is a class which contains a JTextField called inbox1, messageRsetArray is an array which has taken variables from an array. also inbox1 is static. i coulndt get the getters and setter to work. i know its bad practice though.

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  • Unwanted automated creation of new instances of an activity class

    - by Marko
    I have an activity (called Sender) with the most basic UI, only a button that sends a message when clicked. In the onClickListener I only call this method: private void sendSMS(String msg) { PendingIntent pi = PendingIntent.getActivity(this, 0, new Intent(this, Sender.class), 0); PendingIntent pi = PendingIntent.getActivity(this, 0, myIntent, 0); SmsManager sms = SmsManager.getDefault(); sms.sendTextMessage("1477", null, msg, pi, null); } This works ok, the message is sent but every time a message is sent a new instance of Sender is started on top of the other. If I call sendSMS method three times, three new instances are started. I'm quite new to android so I need some help with this, I only want the same Sender to be on all the time

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  • How to get back Hashtable from .txt file use Properties ?

    - by tiendv
    This is code to write hastable to .txt file ! public static void save(String filename, Map<String, String> hashtable) throws IOException { Properties prop = new Properties(); prop.putAll(hashtable); FileOutputStream fos = new FileOutputStream(filename); try { prop.store(fos, prop); } finally { fos.close(); } } How we getback the hashtable from that file ? Thanks

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  • Can I set a timeout for a InputStream's read() function?

    - by Zombies
    I have a DataInputStream that I obtained from a Socket. Is there any way I can set a timeout for dis.read(...)? Currently I spawn a new thread to do the read. While the parent thread does a thread.join(timeout) to wait before interrupting it. I am aware of nio, but I don't think I want to refactor that much at this point. Thanks.

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