diff --git a/org.eclipse.jdt.core.javac/src/org/eclipse/jdt/core/dom/JavacCompilationUnitResolver.java b/org.eclipse.jdt.core.javac/src/org/eclipse/jdt/core/dom/JavacCompilationUnitResolver.java
index 2e8ee130a46..957f83bee08 100644
--- a/org.eclipse.jdt.core.javac/src/org/eclipse/jdt/core/dom/JavacCompilationUnitResolver.java
+++ b/org.eclipse.jdt.core.javac/src/org/eclipse/jdt/core/dom/JavacCompilationUnitResolver.java
@@ -27,6 +27,7 @@
 import javax.tools.FileObject;
 import javax.tools.JavaFileManager;
 import javax.tools.JavaFileObject;
+import javax.tools.JavaFileObject.Kind;
 
 import org.eclipse.core.resources.IFile;
 import org.eclipse.core.resources.ResourcesPlugin;
@@ -43,6 +44,7 @@
 import org.eclipse.jdt.internal.compiler.classfmt.ClassFileConstants;
 import org.eclipse.jdt.internal.compiler.impl.CompilerOptions;
 import org.eclipse.jdt.internal.javac.JavacUtils;
+import org.eclipse.jdt.internal.javac.VirtualFileObject;
 import org.eclipse.jdt.internal.javac.dom.FindNextJavadocableSibling;
 
 import com.sun.tools.javac.file.JavacFileManager;
@@ -145,15 +147,16 @@ public CompilationUnit toCompilationUnit(org.eclipse.jdt.internal.compiler.env.I
 			boolean initialNeedsToResolveBinding, IJavaProject project, List<Classpath> classpaths,
 			NodeSearcher nodeSearcher, int apiLevel, Map<String, String> compilerOptions,
 			WorkingCopyOwner workingCopyOwner, WorkingCopyOwner typeRootWorkingCopyOwner, int flags, IProgressMonitor monitor) {
+		// For comparison
+		//CompilationUnit res2  = CompilationUnitResolver.FACADE.toCompilationUnit(sourceUnit, initialNeedsToResolveBinding, project, classpaths, nodeSearcher, apiLevel, compilerOptions, typeRootWorkingCopyOwner, typeRootWorkingCopyOwner, flags, monitor);
+
 		// TODO currently only parse
 		CompilationUnit res = parse(new org.eclipse.jdt.internal.compiler.env.ICompilationUnit[] { sourceUnit},
 				apiLevel, compilerOptions, flags, project, monitor).get(sourceUnit);
 		if (initialNeedsToResolveBinding) {
 			resolveBindings(res);
 		}
-		// For comparison
-//		CompilationUnit res2  = CompilationUnitResolver.FACADE.toCompilationUnit(sourceUnit, initialNeedsToResolveBinding, project, classpaths, nodeSearcher, apiLevel, compilerOptions, typeRootWorkingCopyOwner, typeRootWorkingCopyOwner, flags, monitor);
-//		//res.typeAndFlags=res2.typeAndFlags;
+		//new CompilationUnitComparator(apiLevel).compare(res, res2);
 //		String res1a = res.toString();
 //		String res2a = res2.toString();
 //
@@ -181,13 +184,17 @@ private Map<org.eclipse.jdt.internal.compiler.env.ICompilationUnit, CompilationU
 		JavacUtils.configureJavacContext(context, compilerOptions, javaProject);
 		var fileManager = (JavacFileManager)context.get(JavaFileManager.class);
 		for (var sourceUnit : sourceUnits) {
-			Path sourceUnitPath;
-			if (sourceUnit.getFileName() == null || sourceUnit.getFileName().length == 0) {
-				sourceUnitPath = Path.of(new File("whatever.java").toURI());
-			} else {
-				sourceUnitPath = Path.of(new File(new String(sourceUnit.getFileName())).toURI());
+			JavaFileObject fileObject = null;
+			if( sourceUnit.getFileName() != null || sourceUnit.getFileName().length != 0 ) {
+				Path p1 = toOSPath(sourceUnit);
+				if( p1 != null ) {
+					fileObject = fileManager.getJavaFileObject(p1);
+				}
+			}
+			if( fileObject == null) {
+				fileObject = new VirtualFileObject(sourceUnit, Kind.OTHER);
 			}
-			var fileObject = fileManager.getJavaFileObject(sourceUnitPath);
+			
 			fileManager.cache(fileObject, CharBuffer.wrap(sourceUnit.getContents()));
 			AST ast = createAST(compilerOptions, apiLevel, context);
 			ast.setDefaultNodeFlag(ASTNode.ORIGINAL);
@@ -242,6 +249,19 @@ private Optional<CompilationUnit> findTargetDOM(Map<JavaFileObject, CompilationU
 		return Optional.empty();
 	}
 
+	private static Path toOSPath(org.eclipse.jdt.internal.compiler.env.ICompilationUnit sourceUnit) {
+		String unitPath = new String(sourceUnit.getFileName());
+		IFile file = ResourcesPlugin.getWorkspace().getRoot().getFile(org.eclipse.core.runtime.Path.fromPortableString(new String(sourceUnit.getFileName())));
+		if (file.isAccessible()) {
+			return file.getLocation().toPath();
+		}
+		File tentativeOSFile = new File(unitPath);
+		if (tentativeOSFile.isFile()) {
+			return tentativeOSFile.toPath();
+		}
+		return null;
+	}
+
 	private AST createAST(Map<String, String> options, int level, Context context) {
 		AST ast = AST.newAST(level, JavaCore.ENABLED.equals(options.get(JavaCore.COMPILER_PB_ENABLE_PREVIEW_FEATURES)));
 		String sourceModeSetting = options.get(JavaCore.COMPILER_SOURCE);
diff --git a/org.eclipse.jdt.core.javac/src/org/eclipse/jdt/internal/javac/VirtualFileObject.java b/org.eclipse.jdt.core.javac/src/org/eclipse/jdt/internal/javac/VirtualFileObject.java
new file mode 100644
index 00000000000..439d9d5a9b4
--- /dev/null
+++ b/org.eclipse.jdt.core.javac/src/org/eclipse/jdt/internal/javac/VirtualFileObject.java
@@ -0,0 +1,100 @@
+package org.eclipse.jdt.internal.javac;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.OutputStream;
+import java.io.Reader;
+import java.io.Writer;
+import java.net.URI;
+
+import javax.lang.model.element.Modifier;
+import javax.lang.model.element.NestingKind;
+import javax.tools.JavaFileObject;
+
+import org.eclipse.jdt.internal.compiler.env.ICompilationUnit;
+
+public class VirtualFileObject implements JavaFileObject {
+	private ICompilationUnit sourceUnit;
+	private Kind kind;
+	public VirtualFileObject(ICompilationUnit sourceUnit, Kind kind) {
+		this.sourceUnit = sourceUnit;
+		this.kind = kind;
+	}
+
+	@Override
+	public URI toUri() {
+		// TODO Auto-generated method stub
+		return null;
+	}
+
+	@Override
+	public String getName() {
+		return new String(sourceUnit.getFileName());
+	}
+
+	@Override
+	public InputStream openInputStream() throws IOException {
+		// TODO Auto-generated method stub
+		return null;
+	}
+
+	@Override
+	public OutputStream openOutputStream() throws IOException {
+		// TODO Auto-generated method stub
+		return null;
+	}
+
+	@Override
+	public Reader openReader(boolean ignoreEncodingErrors) throws IOException {
+		// TODO Auto-generated method stub
+		return null;
+	}
+
+	@Override
+	public CharSequence getCharContent(boolean ignoreEncodingErrors) throws IOException {
+		StringBuilder sb = new StringBuilder();
+		sb.append(this.sourceUnit.getContents());
+		return sb;
+	}
+
+	@Override
+	public Writer openWriter() throws IOException {
+		// TODO Auto-generated method stub
+		return null;
+	}
+
+	@Override
+	public long getLastModified() {
+		// TODO Auto-generated method stub
+		return 0;
+	}
+
+	@Override
+	public boolean delete() {
+		return false;
+	}
+
+	@Override
+	public Kind getKind() {
+		return this.kind;
+	}
+
+	@Override
+	public boolean isNameCompatible(String simpleName, Kind kind) {
+		// TODO Auto-generated method stub
+		return false;
+	}
+
+	@Override
+	public NestingKind getNestingKind() {
+		// TODO Auto-generated method stub
+		return null;
+	}
+
+	@Override
+	public Modifier getAccessLevel() {
+		// TODO Auto-generated method stub
+		return null;
+	}
+
+}