How to suppress Java warnings for specific directories or files such as generated code

Starting with version 3.8 M6, Eclipse (to be exact: the JDT) has built-in functionality for this. It is configurable through a project's build path: Project properties > Java Build Path > Compiler > Source

Announced here: Eclipse 3.8 and 4.2 M6 - New and Noteworthy, called Selectively ignore errors/warnings from source folders. That's also where the screenshot is from. This is the new feature developed on the previously linked Bug 220928.

There is a ticket for this, Bug 220928, that has since been completed for Eclipse 3.8. Please see this answer for details.

If you're stuck with Eclipse 3.7 or lower: The user "Marc" commenting on that ticket created (or at least links to) a plugin called 'warningcleaner' in comment 35. I'm using that with a lot of success while waiting for this feature to be integrated into Eclipse.

It's really quite simple:

1. Install plugin.
2. Right-click project and select "Add/remove generated code nature".
3. Open the project settings (right-click and select "properties").
4. Open the tab 'Warning Cleaner'.
5. Select the source folders you want to ignore the warnings from.

I solved this by using the maven regexp replace plugin - it does not solve the cause, but heals the pain:

<plugin>  <groupId>com.google.code.maven-replacer-plugin</groupId>  <artifactId>maven-replacer-plugin</artifactId>  <version>1.3.2</version>  <executions><execution>  <phase>prepare-package</phase>  <goals>    <goal>replace</goal>  </goals></execution>  </executions>  <configuration><includes>  <include>target/generated-sources/antlr/**/*.java</include></includes><regex>true</regex><regexFlags>  <regexFlag>MULTILINE</regexFlag></regexFlags><replacements>  <replacement>    <token>^public class</token>    <value>@SuppressWarnings("all") public class</value>  </replacement></replacements>  </configuration></plugin>

Note that I did not manage to get the ** notation to work, so you might have to specify path exactly.

See comment below for an improvement on how not to generate duplicate @SupressWarnings