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  • Is it a good idea to close and open hibernate sessions frequently?

    - by Gaurav
    Hi, I'm developing an application which requires that state of entities be read from a database at frequent intervals or triggers. However, once hibernate reads the state, it doesn't re-read it unless I explicitly close the session and read the entity in a new session. Is it a good idea to open a session everytime I want to read the entity and then close it afterwards? How much of an overhead does this put on the application and the database (we use a c3p0 connection pool also)? Will it be enough to simply evict the entity from the session before reading it again?

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  • Find the gender from a name

    - by Ramesh
    Hi guys, I recently confronted with a weird yet interesting question. The questions is as follows: Need to write a program which can give the gender as output based on the name. Example: INPUT -- John Michael Britney OUTPUT-- male male female So this is the output I expect. I tried a lot to solve, but I really was not able to crack it. I will be really thankful to this site for giving me an opportunity to share this question. Actually this is asked in a programming contest as a flyer problem, so I thought this can be programmed.

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  • Weird parsing date string error in Android 2.0 emulator

    - by kknight
    I have a simple test code for testing SimpleDateFormat. This code works well on Eclipse and Android 1.5 emulator, but it failed at Android 2.0 emulator. Does anyone know why? Thanks. public class TemplateActivity extends Activity { /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); TextView tv = new TextView(this); tv.setText(R.string.hello); setContentView(tv); SimpleDateFormat format = new SimpleDateFormat("EEE, dd MMM yyyy HH:mm:ss zzz"); String dateStr = "Mon, 17 May 2010 01:45:41 GMT"; try { Date parsed = format.parse(dateStr); Log.v("Test", parsed.toString()); } catch (ParseException pe) { Log.v("Test", "ERROR: Cannot parse \"" + dateStr + "\""); } } } Log message: V/Test( 400): ERROR: Cannot parse "Mon, 17 May 2010 01:45:41 GMT"

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  • Two collections manyToOne to same primary key

    - by Ethiel
    Hi, guys, I'm coding a web page in Hibernate-JPA and Oracle. I need the following: I have two classes: Place and Home. I need two collections of type Place in every Home: I do the following: Home: @ManyToOne @JoinColumn(name="ID_PLACES") private List<Places>places1; @ManyToOne @JoinColumn(name="ID_PLACES") private List<Places>Places2; However, hibernate got an exception (repeated column) and forces to me to mapping with insert and update to false. How Can I get Two ManyToOne relationship to same primary key with insert a true?.

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  • Generics in return types of static methods and inheritance

    - by Axel
    Generics in return types of static methods do not seem to get along well with inheritance. Please take a look at the following code: class ClassInfo<C> { public ClassInfo(Class<C> clazz) { this(clazz,null); } public ClassInfo(Class<C> clazz, ClassInfo<? super C> superClassInfo) { } } class A { public static ClassInfo<A> getClassInfo() { return new ClassInfo<A>(A.class); } } class B extends A { // Error: The return type is incompatible with A.getClassInfo() public static ClassInfo<B> getClassInfo() { return new ClassInfo<B>(B.class, A.getClassInfo()); } } I tried to circumvent this by changing the return type for A.getClassInfo(), and now the error pops up at another location: class ClassInfo<C> { public ClassInfo(Class<C> clazz) { this(clazz,null); } public ClassInfo(Class<C> clazz, ClassInfo<? super C> superClassInfo) { } } class A { public static ClassInfo<? extends A> getClassInfo() { return new ClassInfo<A>(A.class); } } class B extends A { public static ClassInfo<? extends B> getClassInfo() { // Error: The constructor ClassInfo<B>(Class<B>, ClassInfo<capture#1-of ? extends A>) is undefined return new ClassInfo<B>(B.class, A.getClassInfo()); } } What is the reason for this strict checking on static methods? And how can I get along? Changing the method name seems awkward.

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  • Compare class objects

    - by reto
    I have to compare a class object against a list of pre defined classes. Is it safe to use == or should I use equals()? if (klass == KlassA.class) { } else if (klass == KlassB.class) { } else if (klass == KlassC.class) { } else { } Note: I cannot use instanceof, I don't have an object, I just have the class object. I (mis)use it like an enum in this situation! Thanks!

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  • How often should we write unit tests?

    - by Midnight Blue
    Hi, I am recently introduced to the test-driven approach to development by my mentor at work, and he encourages me to write an unit-test whenenver "it makes sense." I understand some benefits of having a throughout unit-test suite for both regression testing and refractoring, but I do wonder how often and how throughout we should write unit-test. My mentor/development lead asks me to write a new unit test-case for a newly written control flow in a method that is already being tested by the exsisting test class, and I think it is an overkill. How often do you write your unit tests, and how detailed do you think your unit tests should be? Thanks!

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  • Where to store Android preference keys?

    - by pixel
    When I create preference activity I define all preferences in xml file. Every preference has a key defined in this xml. But when I access preference I write: SharedPreferences appPreferences = PreferenceManager.getDefaultSharedPreferences(this); boolean foo_value = appPreferences.getBoolean("foo_key_defined_in_xml", false); Is there any way to avoid acessing "foo_key_defined_in_xml" in hard-coded way? Maybe there is a possibility to access it in R style way?

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  • Mapping enum to a table with hibernate annotation

    - by Thierry-Dimitri Roy
    I have a table DEAL and a table DEAL_TYPE. I would like to map this code: public class Deal { DealType type; } public enum DealType { BASE("Base"), EXTRA("Extra"); } The problem is that the data already exist in the database. And I'm having a hard time mapping the classes to the database. The database looks something like that: TABLE DEAL { Long id; Long typeId; } TABLE DEAL_TYPE { Long id; String text; } I know I could use a simple @OneToMany relationship from deal to deal type, but I would prefer to use an enum. Is this possible? I almost got it working by using a EnumType.ORDINAL type. But unfortunately, my IDs in my deal type table are not sequential, and do not start at 1. Any suggestions?

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  • Detect main class

    - by Daniel
    Hoe can I detect the main class of my application? The one, which is either given on the command line or loaded from the jar given at the command line? If this is not possible, why not?

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  • How to use Boolean variable in c:if

    - by Patriks
    I am using this code in jsf <c:if test="#{sV.done.booleanValue()}"> <option value="#{sV.id}" selected="selected">#{sV.text}</option> </c:if> <c:if test="#{not sV.done.booleanValue()}"> <option value="#{sV.id}">#{sV.text}</option> </c:if> sv is my class containing data (pojo), done is an Boolean variable, I want to display option tag with selected attribute if sV.done is true. But I couldn't make it. Don't know where I am wrong. Otherwise there can be something worong with c? because c:forEach was not working before some time in my case in same page. it can be the reason? Where I am wrong?

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  • Auto injecting logger with guice

    - by koss
    With reference to Guice's custom injections article, its TypeListener performs a check for InjectLogger.class annotation - which can be optional. Removing that check will inject to all Logger.class types. class Log4JTypeListener implements TypeListener { public <T> void hear(TypeLiteral<T> typeLiteral, TypeEncounter<T> typeEncounter) { for (Field field : typeLiteral.getRawType().getDeclaredFields()) { if (field.getType() == Logger.class && field.isAnnotationPresent(InjectLogger.class)) { typeEncounter.register(new Log4JMembersInjector<T>(field)); } } } } I'm tempted to remove "&& field.isAnnotationPresent(InjectLogger.class)" from the listener. If we're using Guice to inject all instances of our Logger, is there any reason not to do it automatically (without need to annotate)?

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  • Why I cannot see an image if I do not use the full name of an image?

    - by Roman
    I try to add an image to JPanel. It works if I specify the full name of the image (including name of all folders). But I want my software to be machine independent (another machine does not have the same folder structure as my machine has). So, I put my image to the same place where the source is and in my code I use just name of the image (no folders' names). It does not work. I put my image into the folder where my executables are. It does not work again. So, why it does not work and what can I do with that?

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  • Whats wrong with this method?

    - by David
    Here's the method: public static String CPUcolor () { System.out.println ("What color am I?") ; String s = getIns() ; System.out.println ("are you sure I'm "+s+"? (Y/N)") ; String a = getIns() ; while (!((a.equals ("y")) || (a.equals ("Y")) || (a.equals ("n")) || (a.equals ("N")))) { System.out.println ("try again") ; a = getIns () ; } if (a.equals ("n") || a.equals("N")) {CPUcolor() ;} System.out.println ("I am "+s) ; return s ; } here is a possible output of this method (y's and n's are user inputs): What color am I? red are you sure I'm red? (Y/N) N What color am I? blue are you sure I'm blue? (Y/N) N What color am I? Yellow are you sure I'm Yellow? (Y/N) y I am Yellow I am blue I am red Why is it that the line's "I am blue" and "I am Blue" printed? Why are they printed in reverse order with red, the first entered, printed last?

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  • converting result set to list

    - by akshay
    how can i conver result set to list? i am using following code but its not working properly private List<User> convertToList(ResultSet rs) { List<User> userList = new ArrayList(); User user = new User(); try { while (rs.next()) { user.setId(rs.getInt("id")); user.setUsername(rs.getString("username")); user.setFname(rs.getString("fname")); user.setLname(rs.getString("lname")); user.setUsertype(rs.getInt("usertype")); user.setPasswd(rs.getString("passwd")); user.setEmail(rs.getString("email")); userList.add(user); } } catch (SQLException ex) { Logger.getLogger(UserDAO.class.getName()).log(Level.SEVERE, null, ex); } finally { closeConnection(); } return userList; }

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  • Why baseclass calls method of subclass?

    - by twlkyao
    I encounter some code like the following: BaseClass: public class BaseClass { String name = "Base"; public BaseClass() { printName(); } public void printName() { System.out.println(name + "——Base"); } } DrivedClass: public class SubClass extends BaseClass { String name = "Sub"; public SubClass() { printName(); } public void printName() { System.out.println(name + "——Sub"); } public static void main(String[] args) { new SubClass(); } } When run the code, the output is: null——Sub Sub——Sub while it should be: Base——Base Sub——Sub I wonder why the BaseClass constructor calls the SubClass method, can anybody explain this? Thanks in advance.

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