Duplicate class ошибка java

Java: «duplicate class» and Mismatched File Name Error

Developers who are new to Java can sometimes have trouble with class and package naming. In fact, the introductory Java forums are filled with threads starting with questions about these areas of Java. In this blog post, I look at some of these errors and some of the causes of these errors.

One of the more obvious errors occurs when a public Java class is named differently than the file that contains the class definition.

This is demonstrated in the next screen snapshot. In this example, a class was declared as public with the name Person , but was saved in a file called Person2.java . The error message is pretty explicit: «class Person is public, should be declared in a file named Person.java»

The «duplicate class» error can sometimes be a little more tricky to resolve. One situation in which this occurs is when two source code directories include the same class with the same package structure. This error looks like that shown in the next screen snapshot.

As the above screen snapshot indicates, the class dustin.examples.Person exists in both the src2 directory and (not shown here) in the src directory («duplicate class: dustin.examples.Person»). Indeed, these are duplicate classes, at least in terms of package and class name.

The «duplicate class» error can also occur when the class is named the same with the same package naming hierarchy, even if one of the classes exists in a directory structure with directory names different than the package names. This is shown in the next screen snapshot.

This screen snapshot demonstrates that the «duplicate error» occurs when the class names and declared package names match even if the source file exists in directories with different names (different even than the declared package structure). What this implies is that if a particular class was copied to another directory without changing the package statement and the new directory was in the source path for javac, the «duplicate class» error will occur.

Another interesting observation from the last example is that javac uses the package statement to decide where to build the .class file rather than using the source file’s location in a directory structure.

In the blog post Java duplicate class error, Morgy describes a situation in which he ran into the «duplicate class» error message (he had neglected to place the class’s package declaration at the top of the class).

Conclusion

In this post, I have attempted to show some common causes of errors that can be troublesome for those new to Java. Specifically, I have demonstrated some of the common causes of the «duplicate class» error and of the public class not matching its file name.

This story, «Java: «duplicate class» and Mismatched File Name Error» was originally published by JavaWorld .

Dustin Marx is a principal software engineer and architect at Raytheon Company. His previous published work for JavaWorld includes Java and Flex articles and «More JSP best practices» (July 2003) and «JSP Best Practices» (November 2001).

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Inspired by Actual Events

Dustin’s Software Development Cogitations and Speculations

My observations and thoughts concerning software development (general development, Java, JavaFX, Groovy, Flex, . ).

Select posts from this blog are syndicated on DZone and Java Code Geeks and were formerly syndicated on JavaWorld.

Dustin’s Pages

Wednesday, February 10, 2010

Java: «duplicate class» and Mismatched File Name Error

Developers who are new to Java can sometimes have trouble with class and package naming. In fact, the introductory Java forums are filled with threads starting with questions about these areas of Java. In this blog post, I look at some of these errors and some of the causes of these errors.

One of the more obvious errors occurs when a public Java class is named differently than the file that contains the class definition.

This is demonstrated in the next screen snapshot. In this example, a class was declared as public with the name Person , but was saved in a file called Person2.java . The error message is pretty explicit: «class Person is public, should be declared in a file named Person.java»

The «duplicate class» error can sometimes be a little more tricky to resolve. One situation in which this occurs is when two source code directories include the same class with the same package structure. This error looks like that shown in the next screen snapshot.

As the above screen snapshot indicates, the class dustin.examples.Person exists in both the src2 directory and (not shown here) in the src directory («duplicate class: dustin.examples.Person»). Indeed, these are duplicate classes, at least in terms of package and class name.

The «duplicate class» error can also occur when the class is named the same with the same package naming hierarchy, even if one of the classes exists in a directory structure with directory names different than the package names. This is shown in the next screen snapshot.

This screen snapshot demonstrates that the «duplicate error» occurs when the class names and declared package names match even if the source file exists in directories with different names (different even than the declared package structure). What this implies is that if a particular class was copied to another directory without changing the package statement and the new directory was in the source path for javac, the «duplicate class» error will occur.

Another interesting observation from the last example is that javac uses the package statement to decide where to build the .class file rather than using the source file’s location in a directory structure.

In the blog post Java duplicate class error, Morgy describes a situation in which he ran into the «duplicate class» error message (he had neglected to place the class’s package declaration at the top of the class).

Conclusion

In this post, I have attempted to show some common causes of errors that can be troublesome for those new to Java. Specifically, I have demonstrated some of the common causes of the «duplicate class» error and of the public class not matching its file name.

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Intellij IDEA 12: Duplicate class error for generated classes #423

I just upgraded to Intellij IDEA 12 Community Edition. On compiling my project I have started getting a duplicate class error on all annotated classes. For ex:

java: activities/BaseMapActivity_.java:16: duplicate class: activities.BaseMapActivity_

I do not get the warning as mentioned in this report on the JetBrains bug tracker: http://youtrack.jetbrains.com/issue/IDEA-94150. I removed the generated source folder from the source path but no luck. I get a no symbol found error then.

The text was updated successfully, but these errors were encountered:

Do you use Maven ?

Nope. Not at the moment.

Btw. I haven’t switched to 2.7 yet. Still on 2.6.

This issue may be resolved by 2.7, it would be nice if you could try to use it 🙂 . At least as a test.

Sure. Back on Idea 11 to get a minor release out. Will give IDEA 12 a shot
with 2.7 in a couple of days.

On Thu, Dec 6, 2012 at 6:10 PM, Pierre-Yves Ricau
notifications@github.comwrote:

This issue may be resolved by 2.7, it would be nice if you could try to
use it 🙂 . At least as a test.

—
Reply to this email directly or view it on GitHubhttps://github.com//issues/423#issuecomment-11083879.

Hate to say: But I have the same problem with IDEA 11 as well. With «mvn clean» as a good workaround.

Strange thing: I never actually found the 2nd class file.

Ok. Tried with Idea 12 again and AA 2.7. These are my steps:

1. Go to Settings > Annotation Processors
2. Enable annotation processing
3. Add androidannotations-2.7.jar in processor path
4. Production sources directory: aa-gen
5. Test sources directory: aa-gen-tests
6. Store generated sources relative to: Module content root/Module output directory (tried both)
7. Include androidannotations-api-2.7.jar in the main module as a dependency
8. Add aa-gen as a Source in the module settings. (tried compiling without it)
9. Re-build project

I get a «cannot find symbol» error for all AA classes. The aa-gen folder is empty.

Problem is that I don’t have maven set up with this project due to issues with library projects with NDK dependencies earlier. I can’t use something like mvn clean.

Let me know if I am going wrong somewhere. This setup works with Idea 11 so am guessing something changed with Idea itself.

I can confirm this bug with AA 2.7, Idea 12 and Maven. mvn clean didn’t help. This might sound silly but I got it working by removing the @EActivity annotation from the main (and removing _ from the activity name in AndroidManifest file). Ran it once, changed back to AA again. But then, if you rebuild, it breaks again. Weird.

Finally got it working! The problem is not with AA but with how you setup your sources directory. I spent a lot of hours setting up Android with Maven + ActionBarSherlock + Roboelectric + AndroidAnnotations with IntelliJ IDEA 12. I’ve written a long blog post (with code snippets and screenshots) on how to setup everything from scratch here — http://www.ashokgelal.com/2012/12/setting-up-intellij-idea-12-with-maven-actionbarsherlock-roboelectric-androidannotations/.

Hopefully, it will be useful for others.

@ashokgelal Thanks! Looks great. I’ll try setting up Maven here again.

If anyone has had success without using Maven, please let me know!

i’ve also written up a small stackoverflow answer on this issue and my experiences (i’m not using maven, just AA and ActionBarSherlock + EventBus). The only problem I have is that everytime i change a source which uses AA, and just «run» my project (or first make my main module), is that it will crash because of an NPE (of an added @bean) in a superclass of that edited source (which also uses AA). So i have to rebuild my entire project every time i want to test something. My main guess is that I don’t see any AA output when I make my main module, so i guess AA is only run on a rebuild.

However I don’t have success with either solution. Apparently the build system was replaced in v12.

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Duplicate class errors with Clover and JAXB or JAXB2 plugin

Related content

Still need help?

The Atlassian Community is here for you.

Symptoms

Project uses JAXB or JAXB2 plugin, which generates sources into src/main/java directory:

When integrating Clover into a build, for example:

the build fails with a number of «duplicate class» errors:

Cause

A build has a following sequence of events:

1. clover:setup is called — Clover instruments regular sources found in ‘src/main/java’ and changes the source root from ‘src/main/java’ to ‘target/clover/src-instrumented’
2. jaxb2:generate is called — JAXB2 generates sources and adds ‘src/main/java’ directory as a source root again
3. javac gets two source roots — ‘src/main/java’ and ‘target/clover/src-instrumented’ — thus it gets «regular» sources twice (original and instrumented), what leads to the duplicate class error

Resolution

There are three solutions possible:

1. Use separate source root for generated sources

Thanks to this, the Clover-for-Maven Plugin will instrument regular sources found in «src/main/java» and redirect source root to the «target/clover/src-instrumented», while the JAXB/JAXB2 plugin will put generated sources into another source root. Clover can instrument or not these generated sources, depending on:

• the order in which JAXB’s ‘generate’ and Clover’s ‘setup’ goals are called
• the includesAllSourceRoots configuration setting for Clover

2. Call JAXB/JAXB2 ‘generate’ goal directly from a command line

Thanks to this, source generation will happen before clover:setup is called and thus:

• the ‘src/main/java’ will contain both regular and generated sources
• the ‘src/main/java’ will be redirected to ‘target/clover/src-instrumented’
• the javac will see only one source root

Example:

3. Reconfigure Clover so that the ‘clover:setup’ is called after a source generation phase

This requires configuring Clover in the POM (it means that the «Automatic Clover integration » feature in Bamboo cannot be used). Thanks to this, Clover will be able to «see» generated sources and could instrument them as well. Set the includesAllSourceRoots property to true (default is false) if you’re interested in code coverage for JAXB generated sources. For instance, the ‘jaxb2:generate’ goal can be bound to the ‘generate-sources’ phase, while the ‘clover:setup’ goal to the ‘process-sources’ phase.

References

Code samples

Checkout sources of the clover-maven-plugin from Bitbucket:

Источник

Друзья, помогите, пожалуйста, разобраться с ошибкой… IDEA? Может, и кода, мне не удалось до конца разобраться в причинах возникновения duplicate class
И почему-то при возникновении ошибки открывается старая, уже решенная задача. Может, надо как-то руками чистить историюпапку с задачами, прежде чем открывать новую?

Далее сам код, если ошибка всё же в нём, а не в обновлении задач JavaRush в IDEA… Хотя валидатор принял.
Но надоело вслепую валидатору кидать решения, без возможности запустить код в среде

package com.javarush.task.task06.task0613;

/*
Кот и статика
*/

public class Solution {
public static void main(String[] args) {
Cat cat1 = new Cat();
Cat cat2 = new Cat();
Cat cat3 = new Cat();
Cat cat4 = new Cat();
Cat cat5 = new Cat();
Cat cat6 = new Cat();
Cat cat7 = new Cat();
Cat cat8 = new Cat();
Cat cat9 = new Cat();
Cat cat10 = new Cat();

System.out.println(Cat.catCount);
}

public static class Cat {
public static int catCount = 0;

public Cat()
{
Cat.catCount++;
}
}
}

Symptoms

Project uses JAXB or JAXB2 plugin, which generates sources into src/main/java directory:

<plugin>
    <groupId>org.jvnet.jaxb2.maven2</groupId>
    <artifactId>maven-jaxb2-plugin</artifactId>
    <version>0.8.0</version>
    <configuration>
        <generateDirectory>src/main/java</generateDirectory>
    </configuration>
    <executions>
        <execution>
            <id>generate</id>
            <goals>
                <goal>generate</goal>
            </goals>
        </execution>
    </executions>
</plugin>

When integrating Clover into a build, for example:

mvn clean clover:setup test clover:aggregate clover:clover

the build fails with a number of «duplicate class» errors:

[INFO] [compiler:compile {execution: default-compile}]
[DEBUG] Using compiler 'javac'.
[DEBUG] Source directories: [/bamboohome/xml-data/build-dir/MYPLAN-JOB1/mymodule/target/clover/src-instrumented
/bamboohome/xml-data/build-dir/MYPLAN-JOB1/mymodule/src/main/java]
...
[INFO] Compiling 123 source files to /bamboohome/xml-data/build-dir/MYPLAN-JOB1/mymodule/target/classes
[INFO] ------------------------------------------------------------------------
[ERROR] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Compilation failure

/bamboohome/xml-data/build-dir/MYPLAN-JOB1/mymodule/target/clover/src-instrumented/com/acme/Foo.java:[16,7] duplicate class: com.acme.Foo

Cause

A build has a following sequence of events:

1. clover:setup is called — Clover instruments regular sources found in ‘src/main/java’ and changes the source root from ‘src/main/java’ to ‘target/clover/src-instrumented’
2. jaxb2:generate is called — JAXB2 generates sources and adds ‘src/main/java’ directory as a source root again
3. javac gets two source roots — ‘src/main/java’ and ‘target/clover/src-instrumented’ — thus it gets «regular» sources twice (original and instrumented), what leads to the duplicate class error

Resolution

There are three solutions possible:

1. Use separate source root for generated sources

Thanks to this, the Clover-for-Maven Plugin will instrument regular sources found in «src/main/java» and redirect source root to the «target/clover/src-instrumented», while the JAXB/JAXB2 plugin will put generated sources into another source root. Clover can instrument or not these generated sources, depending on:

• the order in which JAXB’s ‘generate’ and Clover’s ‘setup’ goals are called
• the includesAllSourceRoots configuration setting for Clover

Example:

<plugin>
    <groupId>org.jvnet.jaxb2.maven2</groupId>
    <artifactId>maven-jaxb2-plugin</artifactId>
    <version>0.8.0</version>
    <configuration>
        <generateDirectory>target/generated-sources/jaxb</generateDirectory>
    </configuration>
    <executions>
        <execution>
            <id>generate</id>
            <goals>
                <goal>generate</goal>
            </goals>
        </execution>
    </executions>
</plugin>

2. Call JAXB/JAXB2 ‘generate’ goal directly from a command line

Thanks to this, source generation will happen before clover:setup is called and thus:

• the ‘src/main/java’ will contain both regular and generated sources
• the ‘src/main/java’ will be redirected to ‘target/clover/src-instrumented’
• the javac will see only one source root

Example:

mvn clean jaxb2:generate clover:setup test clover:aggregate clover:clover

3. Reconfigure Clover so that the ‘clover:setup’ is called after a source generation phase

This requires configuring Clover in the POM (it means that the «Automatic Clover integration » feature in Bamboo cannot be used). Thanks to this, Clover will be able to «see» generated sources and could instrument them as well. Set the includesAllSourceRoots property to true (default is false) if you’re interested in code coverage for JAXB generated sources. For instance, the ‘jaxb2:generate’ goal can be bound to the ‘generate-sources’ phase, while the ‘clover:setup’ goal to the ‘process-sources’ phase.

Example:

<plugin>
    <groupId>org.jvnet.jaxb2.maven2</groupId>
    <artifactId>maven-jaxb2-plugin</artifactId>
    <version>0.8.0</version>
    <configuration>
        <generateDirectory>src/main/java</generateDirectory>
    </configuration>
    <executions>
        <execution>
            <id>generate</id>
			<phase>generate-sources</phase>
            <goals>
                <goal>generate</goal>
            </goals>
        </execution>
    </executions>
</plugin>
<plugin>
    <groupId>com.atlassian.maven.plugins</groupId>
    <artifactId>clover-maven-plugin</artifactId> <!-- Before 4.1.1 it was maven-clover2-plugin -->
    <version>4.1.1</version>
    <configuration>
        <!-- Instrument all source files, also generated by JAXB. Set to false if
        you're not interested in such details (default is false) -->
        <includesAllSourceRoots>true</includesAllSourceRoots>
    </configuration>
    <executions>
        <execution>
            <id>instrument</id>
			<phase>process-sources</phase>
            <goals>
                <goal>setup</goal>
            </goals>
        </execution>
    </executions>
</plugin>

mvn clean test clover:aggregate clover:clover

References

• Using Clover with JAXB plugin
• Duplicate class errors with Clover and jaxws-maven plugin

Code samples

Checkout sources of the clover-maven-plugin from Bitbucket:

hg clone https://bitbucket.org/atlassian/maven-clover2-plugin

Open the src/it/jaxb directory. It contains an example how to configure JAXB and Clover in pom.xml.

While executing some code in the Java you may come across Duplicate Class Error.

Rename the Classes

This situation arises when two different Jar Files (.jar) contain classes with the same name. For example: dist/Project1.jar and dist/lib/Project2.jar are two Jar Files which contain classes having the same name, i.e. com.packagename.Class1.class In that case please rename a class from either jars so that both will have different names.

Reinstall the Java

Uninstall and reinstall the Java software. The steps are given below:

For Windows 8.1/ 8:

1. Press Windows Key + X.

2. Click “Programs and Features”.

3. Right click Java from the installed programs list.

4. Choose Uninstall.

5. Follow the wizard, reboot.

6. Download the setup online and install the program again.

7. Download Java online.

For Earlier Versions of Windows:

1. Click the Start button.

2. Type “Uninstall a program” in the Search Box.

3. Press ENTER.

4. Refer Steps # 3-7 from Windows 8.1/ 8 user’s paragraph.

Download Latest Version of Java

There could be several bugs in the outdated Java version. Download and install the latest version online and then execute your code again.

Delete Java Temporary Files

Java has temporary files stored in particular folder(s) so that they’re accessed from time to time. Delete all temporary files to resolve the problem.

For Windows 8.1/ 8:

1. Press Windows Key + X.

2. Click Control Panel.

3. Click Java Control Panel.

4. In the new dialog click the General tab.

5. Under Temporary Internet Files frame click Settings button.

6. Click Delete Files button.

7. Confirm the action.

8. Reboot the machine when you’re done.

Clear the NetBeans Cache

If you’re getting Duplicate Class error with NetBeans software, please clear the cache as shown below:

For Windows 8.1/ 8 and Earlier Versions:

1. Double click Computer desktop icon.

2. Open the following directory:

C:Users<YourUserName>AppDataLocalNetBeansCache7.2

3. Delete all the cache contents.

Note: The AppData folder is hidden. Unhide it as shown below:

For Windows 8.1/ 8:

1. In My Computer window click the View tab.

2. Check-up “Hidden items” checkbox.

For Earlier Versions of Windows:

1. Click Tools menu, select Folder Options.

2. Click the View tab.

3. Select “Hidden files, folders and drives” option.

4. Click Apply | OK.

Change Annotation Processor Settings

1. Open your Java project that contains a file named APTDemo.jar.

2. Launch Project Properties dialog.

3. Click Annotation Processing panel or Java Compiler, whichever option is present.

4. Check-up “Annotation processing” checkbox.

5. Specify the following values:

Processor Path: androidannotations-2.7.jar

Production Sources Path: aa-gen

Test Sources Path: aa-gen-tests

6. Save the generated sources.

7. Specify following value:

Source: aa-gen

8. Re-build your project and it’ll work fine.