522

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
5
  • 5
    Are there any that generate a switch statement from an Enum with all possible cases? I know you can do this with CTRL+1, but I'd rather use cmd completion.
    – GreenKiwi
    Sep 22, 2011 at 17:21
  • 4
    Can you explain what System.out.println(${word_selection}${});${cursor} means? It sounds like there's a way to select a word and automatically encase it inside a sysout call, am I right? How? May 14, 2013 at 18:34
  • 3
    you highlight the word you want surrounded by sysout call and press Ctrl-Space (then typing in the name of the template if you have lots of highlight aware templates)
    – JReader
    Aug 19, 2014 at 20:22
  • 1
    @JReader what does the ${} do?
    – Roland
    Feb 15, 2017 at 8:43
  • Used as an example in The Tyrannical Mods of Stack Overflow. (But note that there is a lot of factual information in that video which is flat out wrong, for example, that Google would take voting on answers into consideration for search ranking). Nov 25, 2022 at 17:24

46 Answers 46

428
+50

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());
8
  • 3
    I think ${:import ...} only works in newer versions of Eclipse. I'm stuck with 3.2 and it doesn't work for me.
    – Adam Crume
    Jul 7, 2009 at 22:10
  • Not in my version (3.5) either. Does anyone know which version it was introduced in?
    – finnw
    Feb 3, 2010 at 12:35
  • It works fine for me in 3.5 . Feb 3, 2010 at 14:17
  • 6
    I love it! But I put the ${import ...} below the Logger declaration, so that it doesn't add a new line. Jul 21, 2014 at 14:41
  • For log4j2 I had to to set the template to: ${:import(org.apache.logging.log4j.LogManager,org.apache.logging.log4j.Logger)} private static final Logger LOG = LogManager.getLogger(${enclosing_type}.class);
    – TMS
    May 20, 2016 at 10:45
49

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
}
8
  • 48
    i think this is what a method is for :)
    – benmmurphy
    Jul 6, 2009 at 13:37
  • 3
    Err I think you've missed the point... saying that I actually don't know what your point is... it's about code generation not modularity... Jul 6, 2009 at 16:12
  • 21
    I think the point is that adding this much code in a template is cut-and-paste programming for a very common situation. Jun 10, 2011 at 15:23
  • 6
    Yes, you should use a utility method to read a file instead of pasting blocks of code. Write a method yourself, or use Apache commons-io IOUtils. Still, if you make lots of throwaway projects with different classpaths, it can be a pain to add a JAR or link in your utility class just to read a file. Sometimes you just need to write some throwaway code that reads a file, and get on with your life.
    – Mike Clark
    Sep 26, 2013 at 1:07
  • 1
    In Java 7, prefer StandardCharsets.UTF_8 over Charset.forName("UTF-8").
    – Mike Clark
    Sep 26, 2013 at 1:09
33

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).

3
28

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();
5
  • 4
    It's not dead, it's community wiki, so it makes sense to add more templates to it as you find them. There's not really a comprehensive set of these anywhere else... Jul 15, 2010 at 17:07
  • Jon, the time gap between the earlier post and my post was nearly 8 months, thats what compelled to quote so. I couldn't phrase it better than your comment :)
    – questzen
    Jul 23, 2010 at 13:10
  • When I create this as part of a class (a nested enum in a class) I get the name of the class as ${enclosing_type} - intended ? Jun 4, 2012 at 23:30
  • 1
    @Mr_and_Mrs_D, I think that is the point. You get a singleton instance of the class in which you put this template. Now all you need to do is make the enclosing type constructor(s) private and have a pretty safe singleton generator.
    – Mike Adler
    Jun 6, 2012 at 7:29
  • If you want to use this to create an enum use ${primary_type_name} example: public enum ${primary_type_name} { INSTANCE; private ${return_type} ${name} = new ${return_type}(); public ${return_type} ${getName}(${}) { return ${name}; } ${cursor} } Sep 10, 2015 at 15:09
28

Append code snippet to iterate over Map.entrySet():

Template:

${:import(java.util.Map.Entry)}
for (Entry<${keyType:argType(map, 0)}, ${valueType:argType(map, 1)}> ${entry} : ${map:var(java.util.Map)}.entrySet())
{
    ${keyType} ${key} = ${entry}.getKey();
    ${valueType} ${value} = ${entry}.getValue();
    ${cursor}
}

Generated Code:

for (Entry<String, String> entry : properties.entrySet())
{
    String key = entry.getKey();
    String value = entry.getValue();
    |
}

Screenshot

1
  • 1
    Like your pic, it shows me you can use a variable in ${} and that, instead of ${cursor}, enables "tab iteration" between fields. Thanks.
    – WesternGun
    Aug 30, 2018 at 8:57
25

For log, a helpful little ditty to add in the member variable.

private static Log log = LogFactory.getLog(${enclosing_type}.class);
3
  • For writing to a log file manually: ${:import(java.io.PrintWriter, java.io.BufferedWriter, java.io.FileWriter)} try { PrintWriter out = new PrintWriter(new BufferedWriter(new FileWriter(${logFile:var(String)}, true))); out.println(${logLine:var(String)}${cursor}); out.close(); } catch (IOException e) { /* TODO: exception handling */ e.printStackTrace(); } Feb 26, 2015 at 10:30
  • What is a "ditty" (in this context)? Nov 25, 2022 at 17:25
  • @PeterMortensen Ditty by definition is a short song, but in conversational English I've heard it used as pretty much anything repeated.
    – cgp
    Feb 27, 2023 at 3:21
24

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:

${:import(org.mockito.invocation.InvocationOnMock,org.mockito.stubbing.Answer)}doAnswer(new Answer<Object>() {
public Object answer(InvocationOnMock invocation) throws Throwable {
    Object arg1 = invocation.getArguments()[0];
    return null;
}
}).when(${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):

${import:import(java.util.List,com.google.common.collect.Lists)}List<${T}> ${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
2
  • 1
    I'm curious: why would you need to mock the logger? Feb 18, 2012 at 12:53
  • 6
    you can verify the mocked logger was called in case an exception was caught (failure scenario). that's espacially useful if you don't intend to rethrow it but want assert it's not silently ignored.
    – mantrid
    Feb 20, 2012 at 18:46
23

Null Checks!

if( ${word_selection} != null ){
    ${cursor}
}

if( ${word_selection} == null ){
    ${cursor}
}
2
  • The PreConditions.checkNotNull(...) method in Guava is a very readable alternative (especially with static imports) Jun 21, 2013 at 20:33
  • 1
    It's a best practice to check for null (== null) first before checking for not null. Feb 19, 2014 at 2:19
21

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};
5
  • 11
    foreach is available as a standard code assist in Eclipse, I don't see that your template does anything additional to the standard version Jul 3, 2009 at 14:08
  • 4
    Right, and sysout is very innovative template. The question was regarding, useful templates we are using. Jul 3, 2009 at 17:03
  • 4
    your traceout is already available in Eclipse as systrace.
    – dogbane
    Aug 9, 2011 at 9:10
  • 7
    Nice, I want to believe it appears now in Eclipse due to this question. Aug 16, 2011 at 11:23
  • const is available as a standard code assist as static_final (not sure when it was added though)
    – Armand
    Mar 13, 2015 at 19:34
20

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.

3
  • 11
    By default, just typing syso will do the same as sysout. Aug 10, 2011 at 5:25
  • 9
    Beat ya by 25% with sop, though... ;) Nov 7, 2011 at 23:32
  • 2
    Since Eclipse Mars there is a poor step backward on the shortcut "syso" + Ctrl + Space: it will list some classes that have the characters s, y, s and o in their name (due to new CamelCase finding). So, now you have to additionally chose sysout from the list and press Return.
    – bobbel
    Jul 30, 2015 at 15:53
17

Throw an IllegalArgumentException with variable in current scope (illarg):

throw new IllegalArgumentException(${var});

Better

throw new IllegalArgumentException("Invalid ${var} " + ${var});  
14

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.

14

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
1
  • added a wayback machine link Sep 22, 2016 at 17:12
12

slf4j Logging

${imp:import(org.slf4j.Logger,org.slf4j.LoggerFactory)}

private static final Logger LOGGER = LoggerFactory
    .getLogger(${enclosing_type}.class);
10

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);
}
10

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.

9

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}
      }
    });
9

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.

9

strf -> String.format("msg", args) pretty simple but saves a bit of typing.

String.format("${cursor}",)
2
  • 6
    I use String.format("${string}",${objects}) because Eclipse allows me to tab between my string and my list of objects. Feb 13, 2012 at 9:22
  • I use this version: String.format(${word_selection}${},)${cursor}, first select a string then use 'sf' on it. Add the %s and so on... Oct 28, 2014 at 16:25
8

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;
}
5
  • 3
    Just a quick note - According the Maestro known as Joshua Bloch using an Enum should be the preferred method for creating singletons in Java.
    – Pablojim
    Jul 2, 2009 at 18:51
  • Hi Pablojim, Since I posted this template I start reading Effective Java and I changed my singletons implementations to enum. Nevertheless I didn't find a way to have the template generating the enum and thus modifying the class declaration. Have you got this template ? Thanks Manu Jul 3, 2009 at 6:43
  • FYI: Here's the enum singleton pattern electrotek.wordpress.com/2008/08/06/…. I don't particulary like it but then I don't have many singletons. It's easy to turn this into a Java template.
    – pjp
    Jul 3, 2009 at 9:44
  • 1
    For the enum approach, I hope all your singletons make sense as Comparable, Serializable objects, because a lot of Singletons don't (and he wonders why this "...approach has yet to be widely adopted" - because comparability and serialization don't make sense for some singleton classes!) Jun 12, 2011 at 6:04
  • Serializable? Yes. Consider serialization of an Object with a reference to your Singleton. If it is not Serializable, then you might encounter a NPE. If it is (and you don't add methods to overwrite the default de-serialization), then you might get an other instance of your "Singleton". Aug 24, 2012 at 21:45
8

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);
}
1
  • For a solution without reflection see my answer below link Apr 17, 2014 at 13:45
8

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}
8

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<${eventname}Listener> ${eventname}Listeners = new LinkedList<${eventname}Listener>();

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.

2
  • Sending events while being in a lock (synchronized or otherwise) is a deadlock waiting to happen. In this case it would be better to copy the listeners while in a synchronized block and iterating the new list.
    – ssindelar
    Mar 14, 2015 at 5:58
  • Use a ConcurrentLinkedQueue. It does not require locking, because it has a weakly consistent iterator, which never throws a ConcurrentModificationException. Dec 25, 2015 at 14:13
8

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)}
2
  • I like that template. I added a "throws Exception" to ease the testing comfort some more.
    – Torsten
    Oct 24, 2014 at 7:58
  • I like the BDD paradigm. Very nice template for that. And just a note: your very-good-developer-and-friend is gone!
    – bobbel
    Jul 30, 2015 at 15:58
7

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};
}
7

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);
    }
}
5

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.

5

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 ("==", "<", ">" 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!

4

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));
}
4

My favorite few are...

1: Javadoc, to insert doc about the method being a Spring object injection method.

 Method to set the <code>I${enclosing_type}</code> implementation that this class will use.
* 
* @param ${enclosing_method_arguments}<code>I${enclosing_type}</code> 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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