Common Patterns and Best Practices

import org.eclipse.jgit.lib.Repository;
import org.eclipse.jgit.storage.file.FileRepositoryBuilder;
import java.io.File;
import java.io.IOException;

public class RepositoryLifecycle {

    /**
     * Safe repository access pattern using try-with-resources
     */
    public static void withRepository(String repoPath, RepositoryOperation operation)
            throws IOException {
        FileRepositoryBuilder builder = new FileRepositoryBuilder();

        try (Repository repository = builder
                .setGitDir(new File(repoPath, ".git"))
                .readEnvironment()
                .findGitDir()
                .setMustExist(true)
                .build()) {

            operation.execute(repository);
        }
    }

    /**
     * Repository operation interface
     */
    @FunctionalInterface
    public interface RepositoryOperation {
        void execute(Repository repository) throws Exception;
    }

    /**
     * Example usage
     */
    public static void main(String[] args) {
        try {
            withRepository("/path/to/repo", repo -> {
                System.out.println("Repository: " + repo.getDirectory());
                System.out.println("Work tree: " + repo.getWorkTree());
                System.out.println("Is bare: " + repo.isBare());

                // Perform repository operations
                // ...
            });
        } catch (IOException e) {
            System.err.println("Failed to access repository: " + e.getMessage());
        }
    }
}

import org.eclipse.jgit.lib.Repository;
import org.eclipse.jgit.storage.file.FileRepositoryBuilder;
import java.io.File;
import java.io.IOException;
import java.util.function.Supplier;

public class RepositoryFactory {

    private final String basePath;

    public RepositoryFactory(String basePath) {
        this.basePath = basePath;
    }

    /**
     * Create repository supplier for lazy initialization
     */
    public Supplier<Repository> createRepositorySupplier(String repoName) {
        return () -> {
            try {
                return new FileRepositoryBuilder()
                    .setGitDir(new File(basePath, repoName + "/.git"))
                    .setMustExist(true)
                    .build();
            } catch (IOException e) {
                throw new RuntimeException("Failed to open repository: " + repoName, e);
            }
        };
    }

    /**
     * Create repository with retry logic
     */
    public Repository createRepositoryWithRetry(String repoName, int maxRetries)
            throws IOException {
        IOException lastException = null;

        for (int i = 0; i < maxRetries; i++) {
            try {
                return new FileRepositoryBuilder()
                    .setGitDir(new File(basePath, repoName + "/.git"))
                    .build();
            } catch (IOException e) {
                lastException = e;
                if (i < maxRetries - 1) {
                    try {
                        Thread.sleep(100 * (i + 1)); // Exponential backoff
                    } catch (InterruptedException ie) {
                        Thread.currentThread().interrupt();
                        throw new IOException("Interrupted during retry", ie);
                    }
                }
            }
        }

        throw lastException;
    }
}

import org.eclipse.jgit.api.Git;
import org.eclipse.jgit.api.errors.GitAPIException;
import org.eclipse.jgit.errors.RepositoryNotFoundException;
import org.eclipse.jgit.lib.Repository;
import org.eclipse.jgit.storage.file.FileRepositoryBuilder;
import java.io.File;
import java.io.IOException;

public class GitErrorHandling {

    public enum GitOperation {
        CLONE, PUSH, PULL, FETCH, COMMIT, MERGE
    }

    /**
     * Execute Git operation with comprehensive error handling
     */
    public static <T> T executeGitOperation(
            GitOperation operation,
            GitOperationExecutor<T> executor,
            ErrorHandler errorHandler) {

        try {
            return executor.execute();
        } catch (RepositoryNotFoundException e) {
            return errorHandler.handleRepositoryNotFound(operation, e);
        } catch (GitAPIException e) {
            return errorHandler.handleGitApiError(operation, e);
        } catch (IOException e) {
            return errorHandler.handleIoError(operation, e);
        } catch (Exception e) {
            return errorHandler.handleUnexpectedError(operation, e);
        }
    }

    @FunctionalInterface
    public interface GitOperationExecutor<T> {
        T execute() throws Exception;
    }

    public interface ErrorHandler<T> {
        T handleRepositoryNotFound(GitOperation operation, RepositoryNotFoundException e);
        T handleGitApiError(GitOperation operation, GitAPIException e);
        T handleIoError(GitOperation operation, IOException e);
        T handleUnexpectedError(GitOperation operation, Exception e);
    }

    /**
     * Example error handler implementation
     */
    public static class LoggingErrorHandler<T> implements ErrorHandler<T> {
        private final T defaultValue;

        public LoggingErrorHandler(T defaultValue) {
            this.defaultValue = defaultValue;
        }

        @Override
        public T handleRepositoryNotFound(GitOperation operation,
                                         RepositoryNotFoundException e) {
            System.err.println("Repository not found for " + operation + ": " + e.getMessage());
            return defaultValue;
        }

        @Override
        public T handleGitApiError(GitOperation operation, GitAPIException e) {
            System.err.println("Git API error during " + operation + ": " + e.getMessage());
            return defaultValue;
        }

        @Override
        public T handleIoError(GitOperation operation, IOException e) {
            System.err.println("IO error during " + operation + ": " + e.getMessage());
            return defaultValue;
        }

        @Override
        public T handleUnexpectedError(GitOperation operation, Exception e) {
            System.err.println("Unexpected error during " + operation + ": " + e.getMessage());
            e.printStackTrace();
            return defaultValue;
        }
    }
}

import org.eclipse.jgit.api.Git;
import org.eclipse.jgit.api.errors.GitAPIException;
import org.eclipse.jgit.api.errors.TransportException;
import org.eclipse.jgit.lib.Repository;
import java.io.IOException;
import java.util.concurrent.Callable;
import java.util.concurrent.TimeUnit;

public class RetryPattern {

    /**
     * Execute operation with exponential backoff retry
     */
    public static <T> T executeWithRetry(
            Callable<T> operation,
            int maxRetries,
            long initialDelayMs,
            Class<? extends Exception>... retryableExceptions) throws Exception {

        Exception lastException = null;

        for (int attempt = 1; attempt <= maxRetries; attempt++) {
            try {
                return operation.call();
            } catch (Exception e) {
                lastException = e;

                // Check if exception is retryable
                boolean shouldRetry = false;
                for (Class<? extends Exception> retryable : retryableExceptions) {
                    if (retryable.isInstance(e)) {
                        shouldRetry = true;
                        break;
                    }
                }

                if (!shouldRetry || attempt == maxRetries) {
                    break;
                }

                // Exponential backoff
                long delay = initialDelayMs * (1L << (attempt - 1));
                System.out.println("Attempt " + attempt + " failed, retrying in " +
                                 delay + "ms: " + e.getMessage());

                try {
                    TimeUnit.MILLISECONDS.sleep(delay);
                } catch (InterruptedException ie) {
                    Thread.currentThread().interrupt();
                    throw new IOException("Interrupted during retry", ie);
                }
            }
        }

        throw lastException;
    }

    /**
     * Example: Fetch with retry for network issues
     */
    public static void fetchWithRetry(Repository repository) throws Exception {
        executeWithRetry(() -> {
            try (Git git = new Git(repository)) {
                git.fetch().call();
                return null;
            }
        }, 3, 1000, TransportException.class);
    }
}

import org.eclipse.jgit.api.Git;
import org.eclipse.jgit.api.errors.GitAPIException;
import org.eclipse.jgit.lib.Repository;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

public class BatchOperations {

    /**
     * Batch commit multiple files
     */
    public static void commitMultipleFiles(
            Repository repository,
            List<String> filePaths,
            String commitMessage) throws IOException, GitAPIException {

        try (Git git = new Git(repository)) {
            // Add all files
            for (String filePath : filePaths) {
                git.add()
                    .addFilepattern(filePath)
                    .call();
            }

            // Single commit
            git.commit()
                .setMessage(commitMessage)
                .call();
        }
    }

    /**
     * Process commits in batches
     */
    public static void processCommitsInBatches(
            Repository repository,
            int batchSize,
            CommitProcessor processor) throws IOException {

        try (Git git = new Git(repository)) {
            var commits = git.log().all().call();
            List<Object> batch = new ArrayList<>();

            for (var commit : commits) {
                batch.add(commit);

                if (batch.size() >= batchSize) {
                    processor.process(batch);
                    batch.clear();
                }
            }

            // Process remaining commits
            if (!batch.isEmpty()) {
                processor.process(batch);
            }
        }
    }

    @FunctionalInterface
    public interface CommitProcessor {
        void process(List<Object> commits) throws IOException;
    }
}

import org.eclipse.jgit.lib.ObjectId;
import org.eclipse.jgit.lib.Repository;
import java.io.IOException;
import java.util.concurrent.*;

public class GitCache {

    private final Repository repository;
    private final Cache<ObjectId, byte[]> blobCache;
    private final Cache<String, ObjectId> refCache;

    public GitCache(Repository repository, int maxSize) {
        this.repository = repository;
        this.blobCache = new ConcurrentCache<>(maxSize);
        this.refCache = new ConcurrentCache<>(maxSize);
    }

    /**
     * Get blob content with caching
     */
    public byte[] getBlobContent(ObjectId blobId) throws IOException {
        byte[] content = blobCache.get(blobId);
        if (content == null) {
            content = repository.open(blobId).getBytes();
            blobCache.put(blobId, content);
        }
        return content;
    }

    /**
     * Resolve reference with caching
     */
    public ObjectId resolveRef(String refName) throws IOException {
        ObjectId objectId = refCache.get(refName);
        if (objectId == null) {
            objectId = repository.resolve(refName);
            if (objectId != null) {
                refCache.put(refName, objectId);
            }
        }
        return objectId;
    }

    /**
     * Clear cache
     */
    public void clear() {
        blobCache.clear();
        refCache.clear();
    }

    /**
     * Simple cache interface
     */
    private interface Cache<K, V> {
        V get(K key);
        void put(K key, V value);
        void clear();
    }

    /**
     * Concurrent cache implementation using LinkedHashMap
     */
    private static class ConcurrentCache<K, V> implements Cache<K, V> {
        private final ConcurrentHashMap<K, V> cache;
        private final int maxSize;

        public ConcurrentCache(int maxSize) {
            this.maxSize = maxSize;
            this.cache = new ConcurrentHashMap<>();
        }

        @Override
        public V get(K key) {
            return cache.get(key);
        }

        @Override
        public void put(K key, V value) {
            if (cache.size() >= maxSize) {
                // Simple eviction: remove first entry (FIFO)
                if (!cache.isEmpty()) {
                    cache.remove(cache.keys().nextElement());
                }
            }
            cache.put(key, value);
        }

        @Override
        public void clear() {
            cache.clear();
        }
    }
}

import org.eclipse.jgit.lib.Repository;
import java.io.IOException;
import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;

public class ThreadSafeRepository {

    private final Repository repository;
    private final ReadWriteLock lock;

    public ThreadSafeRepository(Repository repository) {
        this.repository = repository;
        this.lock = new ReentrantReadWriteLock();
    }

    /**
     * Execute read operation with shared lock
     */
    public <T> T read(RepositoryReadOperation<T> operation) throws IOException {
        lock.readLock().lock();
        try {
            return operation.execute(repository);
        } finally {
            lock.readLock().unlock();
        }
    }

    /**
     * Execute write operation with exclusive lock
     */
    public <T> T write(RepositoryWriteOperation<T> operation) throws IOException {
        lock.writeLock().lock();
        try {
            return operation.execute(repository);
        } finally {
            lock.writeLock().unlock();
        }
    }

    @FunctionalInterface
    public interface RepositoryReadOperation<T> {
        T execute(Repository repository) throws IOException;
    }

    @FunctionalInterface
    public interface RepositoryWriteOperation<T> {
        T execute(Repository repository) throws IOException;
    }

    /**
     * Close repository safely
     */
    public void close() {
        lock.writeLock().lock();
        try {
            repository.close();
        } finally {
            lock.writeLock().unlock();
        }
    }
}

import org.eclipse.jgit.api.Git;
import org.eclipse.jgit.api.errors.GitAPIException;
import org.eclipse.jgit.lib.Repository;
import java.io.IOException;
import java.util.concurrent.*;

public class ConcurrentGitOperations {

    private final ExecutorService executor;
    private final Repository repository;

    public ConcurrentGitOperations(Repository repository, int threadPoolSize) {
        this.repository = repository;
        this.executor = Executors.newFixedThreadPool(threadPoolSize);
    }

    /**
     * Execute multiple Git operations concurrently
     */
    public List<Future<?>> executeConcurrently(List<Runnable> operations) {
        List<Future<?>> futures = new ArrayList<>();

        for (Runnable operation : operations) {
            futures.add(executor.submit(() -> {
                try (Git git = new Git(repository)) {
                    operation.run();
                } catch (Exception e) {
                    System.err.println("Error in concurrent operation: " + e.getMessage());
                    throw new RuntimeException(e);
                }
            }));
        }

        return futures;
    }

    /**
     * Wait for all operations to complete
     */
    public void awaitCompletion(List<Future<?>> futures, long timeout, TimeUnit unit)
            throws InterruptedException, TimeoutException, ExecutionException {

        for (Future<?> future : futures) {
            future.get(timeout, unit);
        }
    }

    /**
     * Shutdown executor
     */
    public void shutdown() {
        executor.shutdown();
        try {
            if (!executor.awaitTermination(30, TimeUnit.SECONDS)) {
                executor.shutdownNow();
            }
        } catch (InterruptedException e) {
            executor.shutdownNow();
            Thread.currentThread().interrupt();
        }
    }
}

import org.eclipse.jgit.api.Git;
import org.eclipse.jgit.lib.Repository;
import org.eclipse.jgit.revwalk.RevWalk;
import org.eclipse.jgit.treewalk.TreeWalk;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

public class ResourceCleanup {

    /**
     * AutoCloseable wrapper for multiple resources
     */
    public static class GitResources implements AutoCloseable {
        private final List<AutoCloseable> resources;

        public GitResources() {
            this.resources = new ArrayList<>();
        }

        public <T extends AutoCloseable> T register(T resource) {
            resources.add(resource);
            return resource;
        }

        @Override
        public void close() {
            // Close in reverse order (LIFO)
            for (int i = resources.size() - 1; i >= 0; i--) {
                try {
                    resources.get(i).close();
                } catch (Exception e) {
                    System.err.println("Error closing resource: " + e.getMessage());
                }
            }
            resources.clear();
        }
    }

    /**
     * Safe resource usage example
     */
    public static void processRepositorySafely(Repository repository) throws IOException {
        try (GitResources resources = new GitResources()) {
            // Register all resources
            Git git = resources.register(new Git(repository));
            RevWalk walk = resources.register(new RevWalk(repository));
            TreeWalk treeWalk = resources.register(new TreeWalk(repository));

            // Use resources
            ObjectId headId = repository.resolve("HEAD");
            RevCommit head = walk.parseCommit(headId);
            treeWalk.addTree(head.getTree());

            while (treeWalk.next()) {
                // Process tree entries
                System.out.println(treeWalk.getPathString());
            }

            // Resources will be auto-closed in reverse order
        }
    }
}

import org.eclipse.jgit.api.Git;
import org.eclipse.jgit.api.errors.GitAPIException;
import org.eclipse.jgit.lib.Repository;
import org.eclipse.jgit.revwalk.RevCommit;
import java.io.IOException;
import java.util.Iterator;

public class LargeRepositoryHandler {

    /**
     * Process large commit history in chunks
     */
    public static void processLargeCommitHistory(
            Repository repository,
            int chunkSize,
            CommitChunkProcessor processor) throws IOException, GitAPIException {

        try (Git git = new Git(repository)) {
            Iterator<RevCommit> commits = git.log().all().call().iterator();

            while (commits.hasNext()) {
                List<RevCommit> chunk = new ArrayList<>();

                // Collect chunk
                for (int i = 0; i < chunkSize && commits.hasNext(); i++) {
                    chunk.add(commits.next());
                }

                // Process chunk
                processor.process(chunk);

                // Hint to GC
                if (chunk.size() == chunkSize) {
                    System.gc();
                }
            }
        }
    }

    @FunctionalInterface
    public interface CommitChunkProcessor {
        void process(List<RevCommit> chunk) throws IOException;
    }

    /**
     * Memory-efficient file processing
     */
    public static void processFilesEfficiently(
            Repository repository,
            FileProcessor processor) throws IOException {

        // Use streaming where possible
        // Process files one at a time to avoid loading everything into memory

        try (Git git = new Git(repository)) {
            var commits = git.log().setMaxCount(1).call();
            var commit = commits.iterator().next();

            try (var treeWalk = new TreeWalk(repository)) {
                treeWalk.addTree(commit.getTree());
                treeWalk.setRecursive(true);

                while (treeWalk.next()) {
                    // Load file content only when needed
                    byte[] content = repository.open(treeWalk.getObjectId(0)).getBytes();
                    processor.process(treeWalk.getPathString(), content);

                    // Clear reference to allow GC
                    content = null;

                    // Periodically hint GC for large repositories
                    if (treeWalk.getTreeCount() % 1000 == 0) {
                        System.gc();
                    }
                }
            }
        }
    }

    @FunctionalInterface
    public interface FileProcessor {
        void process(String path, byte[] content) throws IOException;
    }
}

import org.eclipse.jgit.api.Git;
import org.eclipse.jgit.api.errors.GitAPIException;
import org.eclipse.jgit.lib.Repository;
import java.io.File;
import java.io.IOException;

public class BuildSystemIntegration {

    /**
     * Git information for build metadata
     */
    public static class BuildMetadata {
        private final String commitId;
        private final String branch;
        private final String tag;
        private final boolean dirty;
        private final String commitMessage;

        public BuildMetadata(String commitId, String branch, String tag,
                           boolean dirty, String commitMessage) {
            this.commitId = commitId;
            this.branch = branch;
            this.tag = tag;
            this.dirty = dirty;
            this.commitMessage = commitMessage;
        }

        // Getters and utility methods
        public String getVersionString() {
            return tag != null ? tag : commitId.substring(0, 8) + (dirty ? "-dirty" : "");
        }
    }

    /**
     * Extract build metadata from Git
     */
    public static BuildMetadata extractBuildMetadata(Repository repository)
            throws IOException, GitAPIException {

        try (Git git = new Git(repository)) {
            // Get current commit
            String commitId = repository.resolve("HEAD").getName();

            // Get branch
            String branch = repository.getBranch();

            // Check if working tree is dirty
            boolean dirty = !git.status().call().isClean();

            // Get commit message
            String commitMessage = git.log().setMaxCount(1).call()
                .iterator().next().getFullMessage();

            // Try to find tag
            String tag = findTagForCommit(repository, commitId);

            return new BuildMetadata(commitId, branch, tag, dirty, commitMessage);
        }
    }

    private static String findTagForCommit(Repository repository, String commitId)
            throws GitAPIException {

        try (Git git = new Git(repository)) {
            for (var ref : git.tagList().call()) {
                if (ref.getObjectId().getName().startsWith(commitId)) {
                    return ref.getName().replace("refs/tags/", "");
                }
            }
        }
        return null;
    }
}

import org.eclipse.jgit.api.Git;
import org.eclipse.jgit.api.errors.GitAPIException;
import org.eclipse.jgit.lib.Repository;
import java.io.File;
import java.io.IOException;
import java.util.Properties;

public class CiCdIntegration {

    /**
     * Generate build properties from Git
     */
    public static Properties generateBuildProperties(Repository repository)
            throws IOException, GitAPIException {

        Properties props = new Properties();

        try (Git git = new Git(repository)) {
            // Basic Git info
            props.setProperty("git.commit.id", repository.resolve("HEAD").getName());
            props.setProperty("git.branch", repository.getBranch());

            // Commit info
            var commit = git.log().setMaxCount(1).call().iterator().next();
            props.setProperty("git.commit.message", commit.getShortMessage());
            props.setProperty("git.commit.user.name", commit.getAuthorIdent().getName());
            props.setProperty("git.commit.user.email", commit.getAuthorIdent().getEmailAddress());
            props.setProperty("git.commit.time", commit.getAuthorIdent().getWhen().toString());

            // Repository state
            boolean isClean = git.status().call().isClean();
            props.setProperty("git.dirty", String.valueOf(!isClean));

            // Remote URL if available
            var config = repository.getConfig();
            String remoteUrl = config.getString("remote", "origin", "url");
            if (remoteUrl != null) {
                props.setProperty("git.remote.origin.url", remoteUrl);
            }
        }

        return props;
    }

    /**
     * Create Git tag for release
     */
    public static void tagRelease(
            Repository repository,
            String version,
            String message,
            boolean annotated) throws GitAPIException {

        try (Git git = new Git(repository)) {
            if (annotated) {
                git.tag()
                    .setName(version)
                    .setMessage(message)
                    .call();
            } else {
                git.tag()
                    .setName(version)
                    .call();
            }

            // Push tag to remote
            git.push()
                .setPushTags()
                .call();
        }
    }
}

import org.eclipse.jgit.api.Git;
import org.eclipse.jgit.api.errors.GitAPIException;
import org.eclipse.jgit.lib.Repository;
import org.eclipse.jgit.storage.file.FileRepositoryBuilder;
import java.io.File;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;

public class GitTestUtils {

    /**
     * Create temporary test repository
     */
    public static TestRepository createTestRepository() throws IOException, GitAPIException {
        Path tempDir = Files.createTempDirectory("jgit-test-");
        File repoDir = tempDir.toFile();

        try (Git git = Git.init().setDirectory(repoDir).call()) {
            // Create initial commit
            File readme = new File(repoDir, "README.md");
            Files.writeString(readme.toPath(), "# Test Repository\n");

            git.add().addFilepattern("README.md").call();
            git.commit().setMessage("Initial commit").call();

            return new TestRepository(git.getRepository(), tempDir);
        }
    }

    public static class TestRepository implements AutoCloseable {
        private final Repository repository;
        private final Path tempDir;

        public TestRepository(Repository repository, Path tempDir) {
            this.repository = repository;
            this.tempDir = tempDir;
        }

        public Repository getRepository() {
            return repository;
        }

        public Path getTempDir() {
            return tempDir;
        }

        @Override
        public void close() throws Exception {
            repository.close();

            // Delete temporary directory
            deleteRecursively(tempDir.toFile());
        }

        private void deleteRecursively(File file) {
            if (file.isDirectory()) {
                for (File child : file.listFiles()) {
                    deleteRecursively(child);
                }
            }
            file.delete();
        }
    }

    /**
     * Create test repository with specific content
     */
    public static Repository createRepositoryWithContent(
            File repoDir,
            String... fileContents) throws IOException, GitAPIException {

        try (Git git = Git.init().setDirectory(repoDir).call()) {
            for (int i = 0; i < fileContents.length; i++) {
                File file = new File(repoDir, "file" + i + ".txt");
                Files.writeString(file.toPath(), fileContents[i]);

                git.add().addFilepattern("file" + i + ".txt").call();
                git.commit().setMessage("Add file " + i).call();
            }
            return git.getRepository();
        }
    }
}

import org.eclipse.jgit.lib.Repository;
import java.io.IOException;

public class MockRepositoryExample {

    /**
     * Repository interface for testing
     */
    public interface TestableRepository {
        String getBranch() throws IOException;
        boolean isBare();
        // Add other methods needed for testing
    }

    /**
     * Real repository wrapper
     */
    public static class RealRepositoryWrapper implements TestableRepository {
        private final Repository repository;

        public RealRepositoryWrapper(Repository repository) {
            this.repository = repository;
        }

        @Override
        public String getBranch() throws IOException {
            return repository.getBranch();
        }

        @Override
        public boolean isBare() {
            return repository.isBare();
        }
    }

    /**
     * Mock repository for unit tests
     */
    public static class MockRepository implements TestableRepository {
        private final String branch;
        private final boolean bare;

        public MockRepository(String branch, boolean bare) {
            this.branch = branch;
            this.bare = bare;
        }

        @Override
        public String getBranch() {
            return branch;
        }

        @Override
        public boolean isBare() {
            return bare;
        }
    }
}

import org.eclipse.jgit.lib.Repository;
import org.eclipse.jgit.revwalk.RevWalk;
import org.eclipse.jgit.revwalk.RevCommit;
import org.eclipse.jgit.lib.ObjectId;
import java.io.IOException;

public class RestrictedRevWalkExample {

    public static void walkRestrictedGraph(Repository repository) throws IOException {
        RevWalk walk = new RevWalk(repository);

        // Only walk commits in master not yet in origin/master
        ObjectId from = repository.resolve("refs/heads/master");
        ObjectId to = repository.resolve("refs/remotes/origin/master");

        walk.markStart(walk.parseCommit(from));
        walk.markUninteresting(walk.parseCommit(to));

        for (RevCommit commit : walk) {
            // Process commits between from and to
            System.out.println(commit.getShortMessage());
        }

        walk.dispose();
    }
}

public class RevWalkWithoutBodies {

    public static void walkWithoutCommitBodies(Repository repository) throws IOException {
        RevWalk walk = new RevWalk(repository);
        walk.setRetainBody(false); // Discard commit bodies

        walk.markStart(walk.parseCommit(repository.resolve("HEAD")));

        for (RevCommit commit : walk) {
            // Can access commit ID but not message/author info
            System.out.println("Commit: " + commit.getId().getName());
            // commit.getFullMessage() would throw exception
        }

        walk.dispose();
    }
}

import java.util.HashSet;
import java.util.Set;

public class ExtractAndDisposeExample {

    public static Set<String> collectAuthorEmails(Repository repository) throws IOException {
        RevWalk walk = new RevWalk(repository);
        Set<String> authorEmails = new HashSet<>();

        walk.markStart(walk.parseCommit(repository.resolve("HEAD")));

        for (RevCommit commit : walk) {
            // Extract needed data
            authorEmails.add(commit.getAuthorIdent().getEmailAddress());
            commit.dispose(); // Release memory for this commit
        }

        walk.dispose();
        return authorEmails;
    }
}

import org.eclipse.jgit.revwalk.RevWalk;
import org.eclipse.jgit.revwalk.RevCommit;
import org.eclipse.jgit.lib.AnyObjectId;
import java.util.Date;

public class CustomRevWalkExample {

    public static class ReviewedRevision extends RevCommit {
        private final Date reviewDate;

        public ReviewedRevision(AnyObjectId id, Date reviewDate) {
            super(id);
            this.reviewDate = reviewDate;
        }

        public Date getReviewDate() {
            return reviewDate;
        }
    }

    public static class ReviewedWalk extends RevWalk {
        public ReviewedWalk(Repository repo) {
            super(repo);
        }

        @Override
        protected RevCommit createCommit(AnyObjectId id) {
            // Create custom commit with review date
            return new ReviewedRevision(id, getReviewDate(id));
        }

        private Date getReviewDate(AnyObjectId id) {
            // Implementation to get review date from external source
            return new Date();
        }
    }
}

public class RevWalkCleanup {

    public static void processWithCleanup(Repository repository) throws IOException {
        // First walk - loads everything into memory
        RevWalk walk1 = new RevWalk(repository);
        // ... perform walk ...
        walk1.dispose(); // Allows GC to reclaim memory

        // Second walk - fresh start, no accumulated objects
        RevWalk walk2 = new RevWalk(repository);
        // ... perform walk ...
        walk2.dispose();
    }
}