René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Line breakpoints never verify in UTF-16 encoded source files","articleBody":"Line breakpoints in Java source files encoded as **UTF-16 LE with BOM** stay unverified forever, even after the class is loaded and the line contains code. The same files debug fine in Eclipse. Our sources are UTF-16 because the ERP development environment we work with generates them that way, so we cannot switch to UTF-8.\n\n##### Environment\n- Operating System: Windows Server 2022\n- JDK version: JRE 25 embedded in the Java extension (language server); debuggee runs on JDK 11\n- Visual Studio Code version: 1.144.0\n- Java extension version: 1.58.0\n- Java Debugger extension version: 0.60.2026102705 (pre-release, bundles com.microsoft.java.debug.plugin 0.53.2)\n\n##### Steps To Reproduce\n1. Create `demo/A.java` as UTF-16 LE with BOM, for example in PowerShell:\n   ```powershell\n   New-Item -ItemType Directory -Force demo | Out-Null\n   [IO.File]::WriteAllText(\"$PWD\\demo\\A.java\", \"package demo;`r`n`r`npublic class A {`r`n    public static void main(String[] a) {`r`n        int x = 1;`r`n        System.out.println(x);`r`n    }`r`n}`r`n\", [Text.UnicodeEncoding]::new($false, $true))\n   ```\n   Content of the file:\n   ```java\n   package demo;\n\n   public class A {\n       public static void main(String[] a) {\n           int x = 1;\n           System.out.println(x);\n       }\n   }\n   ```\n2. Open the folder in VS Code and set a line breakpoint on `int x = 1;`\n3. Debug `demo.A`\n\n##### Current Result\nThe breakpoint stays grey (\"unverified\") and the program runs through without stopping. We see this for every line breakpoint in every UTF-16 file of our real project.\n\n##### Expected Result\nThe breakpoint is verified and execution stops, as it does for UTF-8 files.\n\n##### Additional Informations\nI think the cause is in microsoft/java-debug, `JdtSourceLookUpProvider.readFile`: it reads the file with `new InputStreamReader(new FileInputStream(filePath))`, i.e. with the JVM default charset (UTF-8). For a UTF-16 file the `ASTParser` then finds no package and no type, so no class name is resolved and the breakpoint can never be bound. Calling `readFile` from the shipped plugin jar (0.53.2) on the file above and parsing the result the same way gives no package and no type; with the BOM-aware version below it gives `package demo`, type `A`.\n\nWorkaround I tried: `-Dfile.encoding=UTF-16` in `java.jdt.ls.vmargs` fixes the parsing, but then the language server does not start (`ExceptionInInitializerError` in `org.eclipse.core.net`, caused by `NullPointerException: key can't be null` while loading a native library).\n\nA small change that honours the BOM fixed it for me (tested locally by rebuilding the plugin jar: breakpoints in UTF-16 files verify and stop, UTF-8 files with and without BOM behave as before):\n\n```java\nprivate static String readFile(String filePath) {\n    try {\n        byte[] bytes = Files.readAllBytes(Paths.get(filePath));\n        if (bytes.length >= 3 && (bytes[0] & 0xFF) == 0xEF && (bytes[1] & 0xFF) == 0xBB && (bytes[2] & 0xFF) == 0xBF) {\n            return new String(bytes, 3, bytes.length - 3, StandardCharsets.UTF_8);\n        }\n        if (bytes.length >= 2 && (bytes[0] & 0xFF) == 0xFF && (bytes[1] & 0xFF) == 0xFE) {\n            return new String(bytes, 2, bytes.length - 2, StandardCharsets.UTF_16LE);\n        }\n        if (bytes.length >= 2 && (bytes[0] & 0xFF) == 0xFE && (bytes[1] & 0xFF) == 0xFF) {\n            return new String(bytes, 2, bytes.length - 2, StandardCharsets.UTF_16BE);\n        }\n        return new String(bytes, Charset.defaultCharset());\n    } catch (IOException e) {\n        return \"\";\n    }\n}\n```\n\nUsing the resource charset (`IFile.getCharset()`) where the file belongs to a workspace project might be even better. I'm happy to open a PR in microsoft/java-debug if that helps.\n","author":{"url":"https://github.com/barbarabrugger","@type":"Person","name":"barbarabrugger"},"datePublished":"2026-10-28T21:58:21Z","url":"https://github.com/microsoft/vscode-java-debug/issues/1726"}