Add IntelliJ-style Checkstyle config for core-unittests

[shai-almog]

Motivation

• Ensure the core unit tests module runs Checkstyle with IntelliJ/IDEA defaults (4-space indentation and related whitespace/brace rules) so CI aligns with the project's preferred formatting.

Description

• Add a project-local Checkstyle configuration at maven/core-unittests/checkstyle.xml and update maven/core-unittests/pom.xml to point the maven-checkstyle-plugin configLocation to ${project.basedir}/checkstyle.xml.

Testing

• No automated tests were run as part of this change (Checkstyle will be evaluated by the existing CI verify phase when the pipeline runs).

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Codex Task

[github-actions]

✅ Continuous Quality Report

Test & Coverage

• ✅ Tests: 2283 total, 0 failed, 0 skipped
• 📊 Line coverage: 52.78% [HTML preview] [Download]
  • Lowest covered classes
    • com.codename1.io.rest.RequestBuilder$FetchAsPropertyListActionListener – 0.00%
    • com.codename1.io.rest.RequestBuilder$FetchAsPropertiesActionListener – 0.00%
    • com.codename1.ui.Display$EdtException – 0.00%
    • com.codename1.ui.BrowserWindow$BrowserForm – 0.00%
    • com.codename1.ui.plaf.CSSBorder$LinearGradient – 0.00%
    • com.codename1.io.rest.RequestBuilder$GetAsStringAsyncImplActionListener – 0.00%
    • com.codename1.io.rest.RequestBuilder$GetAsJsonMapActionListener – 0.00%
    • com.codename1.payment.Purchase$SynchronizeReceiptsSyncRunnable – 0.00%
    • com.codename1.io.rest.RequestBuilder$GetAsBytesAsyncImplActionListener – 0.00%
    • com.codename1.io.rest.RequestBuilder$FetchAsJsonMapActionListener – 0.00%

Static Analysis

• ✅ SpotBugs: 0 findings (no issues) [Report archive]
• ❌ PMD: 71 findings (P3: 63, P4: 8) [HTML preview] [Download]
  • Top findings
    • P3: CodenameOne/src/com/codename1/ads/InnerActive.java:43 – This final field could be made static (rule: FinalFieldCouldBeStatic)
    • P3: CodenameOne/src/com/codename1/annotations/Async.java:19 – Class cannot be instantiated and does not provide any static methods or fields (rule: MissingStaticMethodInNonInstantiatableClass)
    • P3: CodenameOne/src/com/codename1/charts/compat/PathMeasure.java:36 – Perhaps 'forceClosed' could be replaced by a local variable. (rule: SingularField)
    • P3: CodenameOne/src/com/codename1/components/Accordion.java:225 – Use opposite operator instead of the logic complement operator. (rule: LogicInversion)
    • P3: CodenameOne/src/com/codename1/facebook/FaceBookAccess.java:1323 – Unnecessary semicolon (rule: UnnecessarySemicolon)
    • …and 66 more
• ❌ Checkstyle: 1374 findings (Error: 1374) [HTML preview] [Download]
  • Top findings
    • Error: CodenameOne/src/com/codename1/javascript/JSFunction.java:1 – File does not end with a newline. (rule: NewlineAtEndOfFileCheck)
    • Error: CodenameOne/src/com/codename1/javascript/JSException.java:1 – File does not end with a newline. (rule: NewlineAtEndOfFileCheck)
    • Error: CodenameOne/src/com/codename1/components/Switch.java:368:15 – Line contains a tab character. (rule: FileTabCharacterCheck)
    • Error: CodenameOne/src/com/codename1/components/Switch.java:752:48 – ';' is not followed by whitespace. (rule: WhitespaceAfterCheck)
    • Error: CodenameOne/src/com/codename1/components/Switch.java:995:24 – ',' is not followed by whitespace. (rule: WhitespaceAfterCheck)
    • …and 1369 more

Generated automatically by the PR CI workflow.