Seeking useful Eclipse Java code templates

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You can create various Java code templates in Eclipse via  Window   Preferences   Java   Editor   Templates  e g   sysout is expanded to   System out println   word selection        cursor    You can activate this by typing sysout followed by CTRL SPACE  What useful Java code templates do you currently use  Include the name and description of it and why it s awesome   I am looking for an original novel use of a template rather than a built-in existing feature    Create Log4J logger Get swt color from display Syncexec - Eclipse Framework Singleton Pattern Enum Singleton Generation Readfile Const Traceout Format String Comment Code Review String format Try Finally Lock Message Format i18n and log Equalsbuilder Hashcodebuilder Spring Object Injection Create FileOutputStream

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Append code snippet to iterate over Map entrySet    Template     import java util Map Entry   for  Entry lt   keyType argType map  0      valueType argType map  1   gt    entry      map var java util Map   entrySet            keyType    key      entry  getKey          valueType    value      entry  getValue          cursor     Generated Code  for  Entry lt String  String gt  entry   properties entrySet          String key   entry getKey        String value   entry getValue

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Hamcrest Test with Static Imports  Here s a template to generate  Test methods with necessary hamcrest imports  if you want to use the new features of JUnit 4 8 2  assertThat  is  hasItems  etc         testType newType org junit Test   public void   testName    throws Exception          Arrange       staticImport importStatic  org hamcrest MatcherAssert     org hamcrest Matchers       cursor          Act         Assert      I already used it many times  when writing test   What is Arrange-Act-Assert

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I just noticed  Duncan Jones already has this template  but adding the   line selection  and using Shift   Alt   Z is a useful tactic   This is maybe only useful as a bit of a hacky fix to some bad design in a project I m working on  but I have a lot of situations where some legacy code is modifying Swing components off the AWT thread and causing intermittent bugs  so to quickly patch these up I use      import javax swing SwingUtilities      Ensure that any Swing components will be invoked only from the AWT thread SwingUtilities invokeLater new Runnable           Override     public void run               line selection   cursor              So I can highlight the offending statements and use Shift   Alt   Z to surround with  I call this template swinvoke

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Format a string  MessageFormat - surround the selection with a MessageFormat       import java text MessageFormat     MessageFormat format   word selection     cursor     This lets me move a cursor to a string  expand the selection to the entire string  Shift-Alt-Up   then Ctrl-Space twice   Lock the selection  lock - surround the selected lines with a try finally lock  Assume the presence of a lock variable     lock  acquire    try         line selection        cursor    finally         lock  release        NB   line selection  templates show up in the Surround With menu  Alt-Shift-Z

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My favorite few are     1  Javadoc  to insert doc about the method being a Spring object injection method    Method to set the  lt code gt I  enclosing type  lt  code gt  implementation that this class will use        param   enclosing method arguments  lt code gt I  enclosing type  lt  code gt  instance    2  Debug window  to create a FileOutputStream and write the buffer s content s to a file  Used for when you want to compare a buffer with a past run  using BeyondCompare   or if you can t view the contents of a buffer  via inspect  because its too large     java io FileOutputStream fos   new java io FileOutputStream  new java io File  c   x x     fos write buffer toString   getBytes     fos flush    fos close

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The following code templates will both create a logger and create the right imports  if needed   SLF4J     import org slf4j Logger org slf4j LoggerFactory   private static final Logger LOG   LoggerFactory getLogger   enclosing type  class     Log4J 2     import org apache logging log4j LogManager org apache logging log4j Logger    private static final Logger LOG   LogManager getLogger   enclosing type  class      Log4J     import org apache log4j Logger   private static final Logger LOG   Logger getLogger   enclosing type  class     Source   JUL     import java util logging Logger   private static final Logger LOG   Logger getLogger   enclosing type  class getName

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One of my beloved is foreach   for    iterable type    iterable element      iterable           cursor      And traceout  since I m using it a lot for tracking   System out println    enclosing type    enclosing method         I just thought about another one and have found it over the Internet some day  const   private static final   type    name    new   type    cursor

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A new JUnit test method       testType newType org junit Test    public void   testname    throws Exception          staticImport importStatic  org junit Assert       cursor        String expected             String actual              Assert assertEquals expected  actual

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Create a new JUnit test case from the selected word   This requires a logger  called  logger  there is a very nice template for that in this thread as well    I m a big fan of this template  because it makes it very easy for me to create unimplemented test cases quickly the minute I think of them  They ll sit there failing on me as a reminder of the case I need to test      import org junit Test  org junit Assert        Test     public void fooTest   throws Throwable           try                 cursor              Assert fail  Not Implemented              catch  Throwable e                 logger error  Failed test   e               throw e                    To use it  type the name of the test case  say testSerializeObject   highlight the word  and hit Ctrl   Space  or whatever you ve configured for code assist    My favorite template for a test case is one that logs exceptions and then rethrows them since I like to see the exceptions in the console rather than in JUnit s exception viewer   Should you prefer System out in your tests over log files  you can always use something similar like      import org junit Test  org junit Assert    Test public void   word selection    throws Exception       try             cursor          Assert fail  Not Implemented          catch  Exception e            System out println  Failed test            e printStackTrace            throw e

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Here is a constructor for non-instantiable classes      Suppress default constructor for noninstantiability  SuppressWarnings  unused   private   enclosing type          throw new AssertionError        This one is for custom exceptions            cursor TODO Auto-generated Exception     public class   Name Exception extends Exception                  TODO Auto-generated Default Serial Version UID             private static final long serialVersionUID   1L                       see Exception Exception               public   Name Exception             super                           see Exception Exception String               public   Name Exception String message            super message                                   see Exception Exception Throwable              public   Name Exception Throwable cause            super cause                                     see Exception Exception String  Throwable              public   Name Exception String message  Throwable cause            super message  cause

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I ve had a lot of use of these snippets  looking for null values and empty strings   I use the  argument test -templates as the first code in my methods to check received arguments   testNullArgument  if    varName     null        throw new NullPointerException           Illegal argument  The argument cannot be null    varName         You may want to change the exception message to fit your company s or project s standard  However  I do recommend having some message that includes the name of the offending argument  Otherwise the caller of your method will have to look in the code to understand what went wrong   A NullPointerException with no message produces an exception with the fairly nonsensical message  null     testNullOrEmptyStringArgument  if    varName     null        throw new NullPointerException           Illegal argument  The argument cannot be null    varName         varName      varName  trim    if    varName  isEmpty          throw new IllegalArgumentException           Illegal argument  The argument cannot be an empty string    varName         You can also reuse the null checking template from above and implement this snippet to only check for empty strings  You would then use those two templates to produce the above code   The above template  however  has the problem that if the in argument is final you will have to amend the produced code some  the   varName      varName  trim   will fail    If you use a lot of final arguments and want to check for empty strings but doesn t have to trim them as part of your code  you could go with this instead   if    varName     null        throw new NullPointerException           Illegal argument  The argument cannot be null    varName       if    varName  trim   isEmpty          throw new IllegalArgumentException           Illegal argument  The argument cannot be an empty string    varName         testNullFieldState  I also created some snippets for checking variables that is not sent as arguments  the big difference is the exception type  now being an IllegalStateException instead    if    varName     null        throw new IllegalStateException           Illegal state  The variable or class field cannot be null    varName         testNullOrEmptyStringFieldState  if    varName     null        throw new IllegalStateException           Illegal state  The variable or class field cannot be null    varName         varName      varName  trim    if    varName  isEmpty          throw new IllegalStateException           Illegal state  The variable or class field                  cannot be an empty string    varName         testArgument  This is a general template for testing a variable  It took me a few years to really learn to appreciate this one  now I use it a lot  in combination with the above templates of course    if      varName    testExpression          throw new IllegalArgumentException           Illegal argument  The argument   varName         varName                    did not pass the test    varName    testExpression         You enter a variable name or a condition that returns a value  followed by an operand          lt        etc  and another value or variable and if the test fails the resulting code will throw an IllegalArgumentException   The reason for the slightly complicated if clause  with the whole expression wrapped in a       is to make it possible to reuse the test condition in the exception message   Perhaps it will confuse a colleague  but only if they have to look at the code  which they might not have to if you throw these kind of exceptions     Here s an example with arrays   public void copy String   from  String   to        if    from length    to length             throw new IllegalArgumentException                   Illegal argument  The argument from length                                  from length                           did not pass the test  from length    to length              You get this result by calling up the template  typing  from length   TAB      to length    The result is way funnier than an  ArrayIndexOutOfBoundsException  or similar and may actually give your users a chance to figure out the problem   Enjoy

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Create everything for an event  Since events are kinda a pain to create in Java--all those interfaces  methods  and stuff to write just for 1 event--I made a simple template to create everything needed for 1 event      import java util List  java util LinkedList  java util EventListener  java util EventObject    private final List lt   eventname Listener gt    eventname Listeners   new LinkedList lt   eventname Listener gt      public final void add  eventname Listener   eventname Listener listener        synchronized   eventname Listeners              eventname Listeners add listener            public final void remove  eventname Listener   eventname Listener listener        synchronized   eventname Listeners              eventname Listeners remove listener            private void raise  eventname Event   eventname Args args        synchronized   eventname Listeners            for   eventname Listener listener     eventname Listeners              listener on  eventname  args            public interface   eventname Listener extends EventListener       public void on  eventname    eventname Args args      public class   eventname Args extends EventObject       public   eventname Args Object source  cursor                 super source             If you have events that share a single EventObject  just delete the customized one inserted by the template and change the appropriate parts of raise      and on         I had written a nice  little  elegant eventing mechanism using a generic interface and generic class  but it wouldn t work due to the way Java handles generics      Edit  1  I ran into the issue where threads were adding removing listeners while an event was taking place  The List can t be modified while in use  so I added synchronized blocks where the list of listeners is being accessed or used  locking on the list itself

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I saw an answer for a template creating a basic test class  and here are some individual calls if you prefer this approach instead   Create setUp method with  Before import     import org junit Before    Before public final void setUp         cursor      Create new test method with  Test import     import org junit Test    Test public final void test  newName         cursor      I use the following for helping with JAXB conversions between types and DTOs   Template for converting existing variable to return value type  works with parameter     return type    name    null   if    var     null          name    new   return type           cursor    return   name

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Create a mock with Mockito  in  Java statements  context       importStatic  org mockito Mockito mock     Type    mockName    mock   Type  class     And in  Java type members       import org mockito Mock   Mock   Type    mockName     Mock a void method to throw an exception      import org mockito invocation InvocationOnMock org mockito stubbing Answer   doThrow   RuntimeException  class  when   mock localVar     mockedMethod    args      Mock a void method to do something      import org mockito invocation InvocationOnMock org mockito stubbing Answer  doAnswer new Answer lt Object gt      public Object answer InvocationOnMock invocation  throws Throwable       Object arg1   invocation getArguments   0       return null       when   mock localVar     mockedMethod    args      Verify mocked method called exactly once      importStatic org mockito Mockito verify org mockito Mockito times   verify   mock localVar   times 1     mockMethod    args      Verify mocked method is never invoked      importStatic org mockito Mockito verify org mockito Mockito never  verify   mock localVar   never      mockMethod    args      New linked list using Google Guava  and similar for hashset and hashmap      import import java util List com google common collect Lists  List lt   T  gt    newName    Lists newLinkedList      Also I use a huge template that generates a Test class  Here is a shortened fragment of it that everyone interested should customize   package   enclosing package    import org junit    import static org junit Assert    import static org hamcrest Matchers    import static org mockito Matchers    import static org mockito Mockito    import org mockito Mockito  import org slf4j Logger  import org mockito InjectMocks  import org mockito Mock  import org mockito runners MockitoJUnitRunner  import org junit runner RunWith      TODO autogenerated test stub  RunWith MockitoJUnitRunner class  public class   primary type name          InjectMocks     protected   testedType    testedInstance         cursor        Mock     protected Logger logger        Before     public void setup   throws Exception               Test     public void shouldXXX   throws Exception              given             when            TODO autogenerated method stub             then         fail  Not implemented                Here goes mockito junit cheetsheet

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For log  a helpful little ditty to add in the member variable   private static Log log   LogFactory getLog   enclosing type  class

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Some more templates here   Includes    Create a date object from a particular date Create a new generic ArrayList Logger setup Log with specified level Create a new generic HashMap Iterate through a map  print the keys and values Parse a time using SimpleDateFormat Read a file line by line Log and rethrow a caught exeption Print execution time of a block of code Create periodic Timer Write a String to a file

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Throw an IllegalArgumentException with variable in current scope  illarg    throw new IllegalArgumentException   var      Better  throw new IllegalArgumentException  Invalid   var        var

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I know I am kicking a dead post  but wanted to share this for completion sake   A correct version of singleton generation template  that overcomes the flawed double-checked locking design  discussed above and mentioned else where   Singleton Creation Template  Name this createsingleton   static enum Singleton       INSTANCE       private static final   enclosing type  singleton   new   enclosing type          public   enclosing type  getSingleton             return singleton            cursor     To access singletons generated using above   Singleton reference Template  Name this getsingleton      type    newName      type  Singleton INSTANCE getSingleton

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strf - gt  String format  msg   args  pretty simple but saves a bit of typing   String format    cursor

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The template for the logger declaration is great   I also create linfo  ldebug  lwarn  lerror for the log levels that I use more often   lerror   logger error   word selection        cursor

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Some additional templates here  Link I - Link II  I like this one   readfile      import java io BufferedReader               java io FileNotFoundException               java io FileReader               java io IOException      BufferedReader in   null     try         in   new BufferedReader new FileReader   fileName           String line        while   line   in readLine       null               process                  catch  FileNotFoundException e          logger error e            catch  IOException e          logger error e         finally         if in    null  in close              cursor     UPDATE  The Java 7 version of this template is      import java nio file Files            java nio file Paths            java nio charset Charset            java io IOException            java io BufferedReader   try  BufferedReader in   Files newBufferedReader Paths get   fileName var String                                                      Charset forName  UTF-8           String line   null      while   line   in readLine       null              cursor          catch  IOException e             todo   handle exception

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With help of plugin  http   code google com p eclipse-log-param   It s possible to add the following template   logger trace    enclosing method     formatted method parameters      And get result   public static void saveUserPreferences String userName  String   preferences        logger trace  saveUserPreferences  userName      userName     preferences      preferences

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list methods - generates the methods for add  removing  counting  and contains for a list  public void add  listname    listtype  toAdd       get  listname s   add toAdd      public void remove  listname    listtype  toRemove       get  listname s   remove toRemove      public   listtype  get  listname  int index       return get  listname s   get index      public int get  listname Count        return get  listname s   size       public boolean contains  listname    listtype  toFind       return get  listname s   contains toFind        cursor    id - inserts the annotations  imports  field  and getter for simple JPA  Id   Id  GeneratedValue strategy   GenerationType IDENTITY  private Long id   public Long getId        return id       cursor     import  javax persistence GenerationType javax persistence GeneratedValue javax persistence Id

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Post Java 7  a great way to set up loggers which need  or prefer  static references to the enclosing class is to use the newly introduced MethodHandles API to get the runtime class in a static context   An example snippet for SLF4J is   private static final Logger logger   LoggerFactory getLogger MethodHandles lookup   lookupClass       Aside from being a simple snippet in any IDE  it is also less brittle if you refactor certain functionality into another class because you won t accidentally carry the class name with it

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This prints an entire object  assumes you have already initiated a log4j LOGGER object         import org codehaus jackson map ObjectMapper        If check to avoid argument evaluation costs   if  LOGGER isDebugEnabled              try               LOGGER debug  Object   Object         n                    new ObjectMapper   writeValueAsString   Object               catch  JsonGenerationException e                LOGGER info e toString               catch  JsonMappingException e                LOGGER info e toString               catch  IOException e                LOGGER info e toString

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EasyMock templates  Create Mock     importStatic org easymock EasyMock createMock     type    name    createMock   type  class     Reset Mock     importStatic org easymock EasyMock reset   reset   var      Replay Mock     importStatic org easymock EasyMock replay   replay   var      Verify Mock     importStatic org easymock EasyMock verify   verify   var

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public int hashCode   public boolean equals Object    Using explicit tests rather than reflection which is slower and might fail under a Security Manager  EqualsBuilder javadoc    The template contains 20 members  You can move through them with TAB  Once finished  the remaining calls to apppend   have to be removed      import org apache commons lang builder HashCodeBuilder  org apache commons lang builder EqualsBuilder    Override public int hashCode         return new HashCodeBuilder            append   field1 field            append   field2 field            append   field3 field            append   field4 field            append   field5 field            append   field6 field            append   field7 field            append   field8 field            append   field9 field            append   field10 field            append   field11 field            append   field12 field            append   field13 field            append   field14 field            append   field15 field            append   field16 field            append   field17 field            append   field18 field            append   field19 field            append   field20 field            toHashCode        Override public boolean equals Object obj        if  obj    null            return false            if  obj    this            return true            if  obj getClass      getClass              return false              enclosing type  rhs      enclosing type   obj      return new EqualsBuilder                append   field1   rhs   field1                append   field2   rhs   field2                append   field3   rhs   field3                append   field4   rhs   field4                append   field5   rhs   field5                append   field6   rhs   field6                append   field7   rhs   field7                append   field8   rhs   field8                append   field9   rhs   field9                append   field10   rhs   field10                append   field11   rhs   field11                append   field12   rhs   field12                append   field13   rhs   field13                append   field14   rhs   field14                append   field15   rhs   field15                append   field16   rhs   field16                append   field17   rhs   field17                append   field18   rhs   field18                append   field19   rhs   field19                append   field20   rhs   field20    cursor               isEquals

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Vector to Array   array type      v var Vector  Array   new   array type    v  size       v  copyInto   v Array

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Invoke code on the GUI thread  I bind the following template to the shortcut slater to quickly dispatch code on the GUI thread      import javax swing SwingUtilities   SwingUtilities invokeLater new Runnable                  Override       public void run               cursor

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Inner listener class for SWT and plugin development     imports import org eclipse swt widgets Listener   private class   className  implements Listener        Override     public void handleEvent Event e            final Widget w   e widget

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Nothing fancy for code production - but quite useful for code reviews  I have my template coderev low med high do the following         Code Review  Low Importance           TODO  Insert problem with code here           And then in the Tasks view - will show me all of the code review comments I want to bring up during a meeting

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A little tip on sysout -- I like to renamed it to  sop   Nothing else in the java libs starts with  sop  so you can quickly type  sop  and boom  it inserts

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Code Section    --------------------------------------------------------------                            title    --------------------------------------------------------------   cursor    Use this template to make commenting sections of code easier  it s not very complex  but has saved me lots of time

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Here s a foreach that will work for iterating over a List lt Stuff gt   The optional content inside the loop is for finding an element in the list and return it   for    t elemType w   elem    w collection         if  elem get equals   localVar             return elem          return null

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Spring Injection  I know this is sort of late to the game  but here is one I use for Spring Injection in a  class      import org springframework beans factory annotation Autowired   private   class to inject    var name     Autowired public void set  class to inject    class to inject    var name       this   var name      var name      public   class to inject  get  class to inject        return this   var name

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And an equalsbuilder  hashcodebuilder adaptation      import org apache commons lang builder EqualsBuilder org apache commons lang builder HashCodeBuilder    Override public boolean equals Object obj        return EqualsBuilder reflectionEquals this  obj       Override public int hashCode         return HashCodeBuilder reflectionHashCode this

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Bean Property  private   Type    property    public   Type  get  Property          return   property      public void set  Property    Type    property           propertyChangeSupport  firePropertyChange    property    this   property       this   property      property        PropertyChangeSupport  private PropertyChangeSupport   propertyChangeSupport    new PropertyChangeSupport this     import java beans PropertyChangeSupport java beans PropertyChangeListener   public void addPropertyChangeListener PropertyChangeListener listener        propertyChangeSupport  addPropertyChangeListener listener      public void addPropertyChangeListener String propertyName  PropertyChangeListener listener        propertyChangeSupport  addPropertyChangeListener propertyName  listener      public void removePropertyChangeListener PropertyChangeListener listener        propertyChangeSupport  removePropertyChangeListener listener      public void removePropertyChangeListener String propertyName  PropertyChangeListener listener        propertyChangeSupport  removePropertyChangeListener propertyName  listener

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I use following templates for Android development   Verbose  Logv   Log v TAG    word selection        cursor    Debug  Logd   Log d TAG    word selection        cursor    Info  Logi   Log i TAG    word selection        cursor    Warn  Logw   Log w TAG    word selection        cursor    Error  Loge   Log e TAG    word selection        cursor    Assert  Loga   Log a TAG    word selection        cursor    TAG is a Constant I define in every activity

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Get an SWT color from current display   Display getCurrent   getSystemColor SWT COLOR   cursor     Suround with syncexec  PlatformUI getWorkbench   getDisplay   syncExec new Runnable        public void run              line selection   cursor              Use the singleton design pattern          The shared instance      private static   enclosing type  instance   new   enclosing type             Private constructor      private   enclosing type          super              Returns this shared instance         returns The shared instance     public static   enclosing type  getInstance         return instance

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slf4j Logging    imp import org slf4j Logger org slf4j LoggerFactory    private static final Logger LOGGER   LoggerFactory      getLogger   enclosing type  class

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Insert test methods should-given-when-then  I saw a similar version to this one recently while pair programming with a very good developer and friend  and I think it could be a nice addition to this list   This template will create a new test method on a class  following the Given - When - Then approach from the behavior-driven development  BDD  paradigm on the comments  as a guide for structuring the code  It will start the method name with  should  and let you replace the rest of the dummy method name  CheckThisAndThat  with the best possible description of the test method responsibility  After filling the name  TAB will take you straight to the    Given section  so you can start typing your preconditions   I have it mapped to the three letters  tst   with description  Test methods should-given-when-then      I hope you find it as useful as I did when I saw it    Test public void should  CheckThisAndThat          Assert fail  Not yet implemented           Given       cursor          When          Then      import org junit Test  org junit Assert

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This takes a lot of the grunt work out of printing   logging local values  It automatically captures the variable name within a String  This saves a lot of typing and typo correction   The template          1 var         1 var    It has two pitfalls   Although you are prompted to select a local   parameter   field  this does not include primitives     Prompting occurs most whenever the code is compiled with no errors  Often using this macro yields temporarily broken syntax  so some juggling is necessary to insert multiple variables  Nothing close to the convenience of not having typos in variable names

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Null Checks   if    word selection     null          cursor     if    word selection     null          cursor

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When testing around with code I sometimes missed out on deleting some syso s  So I made myself a template called syt    System out println   word selection          todo  remove  cursor    Before I compile I always check my TODOs and will never forget to delete a System out again

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I like a generated class comment like this          I             Id        The  I     immediately encourages the developer to describe what the class does  I does seem to improve the problem of undocumented classes   And of course the  Id  is a useful CVS keyword

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I use this for MessageFormat  using Java 1 4    That way I am sure that I have no concatenations that are hard to extract when doing internationalization  i18n  String msg      message    Object   params      params    MessageFormat format msg  params     Also for logging   log  if logger isDebugEnabled       String msg      message      NLS-1   Object   params      params      logger debug MessageFormat format msg  params

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