Fix folding of 2 consecutive methods

If the second method starts in the same line the first one ends then
there will still be 2 foldings.

Fixes eclipse-jdt#1539

org.eclipse.jdt.text.tests/src/org/eclipse/jdt/text/tests/JdtTextTestSuite.java

@@ -20,6 +20,7 @@
 import org.eclipse.jdt.text.tests.codemining.CodeMiningTriggerTest;
 import org.eclipse.jdt.text.tests.codemining.ParameterNamesCodeMiningTest;
 import org.eclipse.jdt.text.tests.contentassist.ContentAssistTestSuite;
+import org.eclipse.jdt.text.tests.folding.FoldingTest;
 import org.eclipse.jdt.text.tests.semantictokens.SemanticTokensProviderTest;
 import org.eclipse.jdt.text.tests.spelling.SpellCheckEngineTestCase;
 import org.eclipse.jdt.text.tests.templates.TemplatesTestSuite;
@@ -70,6 +71,7 @@
 	JavaElementPrefixPatternMatcherTest.class,
 	CodeMiningTriggerTest.class,
 	ParameterNamesCodeMiningTest.class,
+	FoldingTest.class
 })
 public class JdtTextTestSuite {
 }

org.eclipse.jdt.text.tests/src/org/eclipse/jdt/text/tests/folding/FoldingTest.java

@@ -0,0 +1,113 @@
+/*******************************************************************************
+ * Copyright (c) 2025 Vector Informatik GmbH and others.
+ *
+ * This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License 2.0
+ * which accompanies this distribution, and is available at
+ * https://www.eclipse.org/legal/epl-2.0/
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ *
+ * Contributors:
+ *     Vector Informatik GmbH - initial API and implementation
+ *******************************************************************************/
+package org.eclipse.jdt.text.tests.folding;
+
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.util.ArrayList;
+import java.util.Iterator;
+import java.util.List;
+
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Rule;
+import org.junit.Test;
+
+import org.eclipse.jdt.testplugin.JavaProjectHelper;
+
+import org.eclipse.core.runtime.CoreException;
+
+import org.eclipse.jface.text.IRegion;
+import org.eclipse.jface.text.Position;
+import org.eclipse.jface.text.Region;
+import org.eclipse.jface.text.source.Annotation;
+import org.eclipse.jface.text.source.projection.ProjectionAnnotation;
+import org.eclipse.jface.text.source.projection.ProjectionAnnotationModel;
+
+import org.eclipse.ui.PartInitException;
+
+import org.eclipse.jdt.core.ICompilationUnit;
+import org.eclipse.jdt.core.IJavaProject;
+import org.eclipse.jdt.core.IPackageFragment;
+import org.eclipse.jdt.core.IPackageFragmentRoot;
+import org.eclipse.jdt.core.JavaModelException;
+
+import org.eclipse.jdt.ui.tests.core.rules.ProjectTestSetup;
+
+import org.eclipse.jdt.internal.ui.javaeditor.EditorUtility;
+import org.eclipse.jdt.internal.ui.javaeditor.JavaEditor;
+
+public class FoldingTest {
+	@Rule
+	public ProjectTestSetup projectSetup= new ProjectTestSetup();
+
+	private IJavaProject jProject;
+
+	private IPackageFragmentRoot sourceFolder;
+
+	private IPackageFragment packageFragment;
+
+	@Before
+	public void setUp() throws CoreException {
+		jProject= projectSetup.getProject();
+		sourceFolder= jProject.findPackageFragmentRoot(jProject.getResource().getFullPath().append("src"));
+		if (sourceFolder == null) {
+			sourceFolder= JavaProjectHelper.addSourceContainer(jProject, "src");
+		}
+		packageFragment= sourceFolder.createPackageFragment("org.example.test", false, null);
+	}
+
+	@After
+	public void tearDown() throws CoreException {
+		JavaProjectHelper.delete(jProject);
+	}
+
+	@Test
+	public void testMethodDeclarationFoldingWithSameLineStart() throws JavaModelException, PartInitException {
+		String str= """
+				package org.example.test;
+				public class Q {
+				    void a() {
+				  int i = 0;
+				    }void b() {
+				    }
+				}
+				""";
+		List<IRegion> regions= getProjectionRangesOfFile(str);
+		assertTrue(regions.size() == 2);
+
+		regions.sort((r1, r2) -> Integer.compare(r1.getOffset(), r2.getOffset()));
+		IRegion methodARegion= regions.get(0);
+		IRegion methodBRegion= regions.get(1);
+		int methodAEnd= methodARegion.getOffset() + methodARegion.getLength();
+		int methodBStart= methodBRegion.getOffset();
+		assertTrue(methodBStart >= methodAEnd, String.format("void b() should start void a(){}, but it wasnt. void b() started at %d and void a() ended at %d", methodBStart, methodAEnd));
+	}
+
+	private List<IRegion> getProjectionRangesOfFile(String str) throws JavaModelException, PartInitException {
+		ICompilationUnit cu= packageFragment.createCompilationUnit("TestFolding.java", str, true, null);
+		JavaEditor editor= (JavaEditor) EditorUtility.openInEditor(cu);
+		ProjectionAnnotationModel model= editor.getAdapter(ProjectionAnnotationModel.class);
+		List<IRegion> regions= new ArrayList<>();
+		Iterator<Annotation> it= model.getAnnotationIterator();
+		while (it.hasNext()) {
+			Annotation a= it.next();
+			if (a instanceof ProjectionAnnotation) {
+				Position p= model.getPosition(a);
+				regions.add(new Region(p.getOffset(), p.getLength()));
+			}
+		}
+		return regions;
+	}
+}

org.eclipse.jdt.ui/ui/org/eclipse/jdt/ui/text/folding/DefaultJavaFoldingStructureProvider.java

@@ -1279,23 +1279,15 @@ protected final IRegion alignRegion(IRegion region, FoldingStructureComputationC
 		IDocument document= ctx.getDocument();
 
 		try {
-
 			int start= document.getLineOfOffset(region.getOffset());
-			int end= document.getLineOfOffset(region.getOffset() + region.getLength());
+			int end= document.getLineOfOffset(region.getOffset() + region.getLength() - 1);
 			if (start >= end)
 				return null;
-
-			int offset= document.getLineOffset(start);
-			int endOffset;
-			if (document.getNumberOfLines() > end + 1)
-				endOffset= document.getLineOffset(end + 1);
-			else
-				endOffset= document.getLineOffset(end) + document.getLineLength(end);
+			int offset = document.getLineOffset(start);
+			int endOffset = document.getLineOffset(end);
 
 			return new Region(offset, endOffset - offset);
-
 		} catch (BadLocationException x) {
-			// concurrent modification
 			return null;
 		}
 	}