Gradle "Task :compileJava FAILED" - Fix Compilation in CI

Task :compileJava FAILED means javac rejected your source. Gradle prints the compiler diagnostics just above the failure line - a missing symbol, a type error, or a missing dependency on the compile classpath.

What this error means

The build stops with > Task :compileJava FAILED and a Compilation failed; see the compiler error output for details, preceded by javac errors naming files, lines, and symbols.

> Task :app:compileJava FAILED
/app/src/main/java/com/example/App.java:42: error: cannot find symbol
        calc.calculate(10);
            ^
  symbol:   method calculate(int)
2 errors

Common causes

A real source error

A missing import, renamed method, or type mismatch makes javac fail. Gradle surfaces the compiler’s own diagnostics above the FAILED line.

Missing dependency or generated source in CI

A dependency absent from the compile classpath, or annotation-processed/generated code that was not produced, makes references unresolvable in the pipeline.

How to fix it

Read the javac errors and reproduce locally

The file:line/error lines pinpoint the failure. Re-run the single task with more output.

./gradlew :app:compileJava --console=plain --info

Check the compile classpath and codegen

1. Confirm the dependency providing the missing symbol is on implementation/compileOnly.
2. Run the task that generates sources before compileJava if codegen is involved.
3. Build a clean checkout so stale outputs do not mask a missing dependency.

How to prevent it

• Build clean in CI so stale outputs never hide compile errors.
• Declare dependencies in the correct configuration (implementation vs compileOnly).
• Run compileJava on every PR to catch source errors before merge.

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