chore: import upstream snapshot with attribution

tests/fixtures/SampleJava.java

@@ -0,0 +1,66 @@
+package com.example.auth;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Optional;
+
+public interface UserRepository {
+    Optional<User> findById(int id);
+    void save(User user);
+}
+
+class User {
+    private int id;
+    private String name;
+    private String email;
+
+    public User(int id, String name, String email) {
+        this.id = id;
+        this.name = name;
+        this.email = email;
+    }
+
+    public int getId() { return id; }
+    public String getName() { return name; }
+    public String getEmail() { return email; }
+}
+
+class InMemoryRepo implements UserRepository {
+    private Map<Integer, User> users = new HashMap<>();
+
+    @Override
+    public Optional<User> findById(int id) {
+        return Optional.ofNullable(users.get(id));
+    }
+
+    @Override
+    public void save(User user) {
+        users.put(user.getId(), user);
+        System.out.println("Saved user " + user.getId());
+    }
+}
+
+class UserService {
+    private final UserRepository repo;
+
+    public UserService(UserRepository repo) {
+        this.repo = repo;
+    }
+
+    public User createUser(String name, String email) {
+        User user = new User(1, name, email);
+        repo.save(user);
+        return user;
+    }
+
+    public Optional<User> getUser(int id) {
+        return repo.findById(id);
+    }
+}
+
+class CachedRepo extends InMemoryRepo {
+    @Override
+    public void save(User user) {
+        super.save(user);
+    }
+}