How to Fix “The Process Cannot Access the File Because It Is Being Used by Another Process” in Android Studio

While developing Android applications, you may encounter build errors that prevent your project from compiling successfully. One common error is:

Execution failed for task ':app:mergeDebugJavaResource'.

Caused by:
java.nio.file.FileSystemException:
out.jar: The process cannot access the file because it is being used by another process.

This error can be frustrating, especially for beginners. Fortunately, the cause is usually simple: another application or process has locked a file that Android Studio needs during the build process.

In this article, we’ll explain what causes this problem and provide step-by-step solutions to fix it.

Understanding the Error

Android Studio uses Gradle to build your application. During the build process, Gradle creates temporary files inside the build directory.

One of these files may be:

app/build/intermediates/merged_java_res/debug/out.jar

If another process is using this file, Gradle cannot modify or overwrite it, causing the build to fail.

Typical error message:

java.nio.file.FileSystemException:
out.jar: The process cannot access the file because it is being used by another process.

Common Causes

1. Android Studio Background Process

Sometimes Android Studio itself keeps a file handle open during a previous build.

2. Gradle Daemon

The Gradle daemon may become stuck and continue locking generated files.

3. Antivirus Software

Windows Defender or third-party antivirus solutions often scan newly generated JAR files and temporarily lock them.

4. File Synchronization Tools

Applications such as:

• OneDrive
• Google Drive
• Dropbox
• Backup software

may monitor project folders and lock files while synchronizing them.

5. Java Processes Running in Background

Old Java or Gradle processes may still be running after a failed build.

Solution 1: Clean and Rebuild the Project

The simplest fix is often cleaning the project.

Using Android Studio

Select:

Build → Clean Project

Then:

Build → Rebuild Project

Using Command Line

gradlew clean
gradlew build

Solution 2: Delete the Build Folder

Close Android Studio.

Navigate to:

app/build/

Delete the entire build directory.

You can also remove:

.gradle/

from the project root.

Reopen Android Studio and rebuild the project.

Solution 3: Stop All Gradle Processes

Open Command Prompt:

gradlew --stop

This stops all running Gradle daemons.

You can then restart Android Studio and try building again.

Solution 4: Kill Java Processes

Open Task Manager.

Look for:

java.exe
javaw.exe
gradle.exe

Terminate any processes related to old Android Studio builds.

Alternatively, from Command Prompt:

taskkill /F /IM java.exe
taskkill /F /IM javaw.exe

Be careful if other Java applications are running.

Solution 5: Exclude the Project from Antivirus Scanning

Windows Defender is a common cause of file locking issues.

Add an Exclusion

Open:

Windows Security

Navigate to:

Virus & Threat Protection
→ Manage Settings
→ Exclusions

Add exclusions for:

C:\Users\YourUser\AndroidStudioProjects\

or the specific project folder.

This prevents Windows Defender from locking generated build files.

Solution 6: Disable Real-Time Synchronization

If your project is stored in:

OneDrive
Dropbox
Google Drive

move it to a local directory such as:

C:\Development\

Cloud synchronization software frequently causes build file locking.

Solution 7: Invalidate Android Studio Caches

Sometimes Android Studio’s internal cache becomes corrupted.

Navigate to:

File → Invalidate Caches

Select:

Invalidate and Restart

Android Studio will rebuild its indexes after restarting.

Solution 8: Restart the Computer

If you’re unsure which process is locking the file, a full system restart often clears the problem immediately.

This is especially effective after failed builds or IDE crashes.

Advanced Troubleshooting: Find the Process Locking the File

Microsoft provides a utility called Process Explorer.

Steps

1. Download Process Explorer.
2. Run as Administrator.
3. Press:

Ctrl + F

4. Search for:

out.jar

Process Explorer will show exactly which application is using the file.

You can then terminate the offending process.

Preventing Future Problems

To reduce the chance of encountering this issue:

• Keep Android Studio updated.
• Keep Gradle updated.
• Avoid storing projects in synchronized cloud folders.
• Exclude project directories from antivirus scanning.
• Regularly clean old build artifacts.
• Stop unused Gradle daemons.

Example Fix Workflow

When you encounter:

Execution failed for task ':app:mergeActivDebugJavaResource'

Follow this order:

1. Close Android Studio.
2. Run:

gradlew --stop

3. Delete:

app/build/
.gradle/

4. Reopen Android Studio.
5. Clean Project.
6. Rebuild Project.

In most cases, the issue is resolved immediately.

Conclusion

The “The process cannot access the file because it is being used by another process” error in Android Studio is usually caused by a file lock created by Gradle, Java, antivirus software, or synchronization tools.

Although the error looks intimidating, it is rarely related to your source code. By cleaning the project, stopping Gradle daemons, deleting build artifacts, and checking for applications that lock files, you can quickly restore normal builds and continue development.

Understanding how Android Studio, Gradle, and the Windows file system interact will help you diagnose similar build problems more efficiently in the future.