Small improvements, part 2

.github/copilot-instructions.md

@@ -51,6 +51,11 @@ Common pitfalls and fixes
 Linting & style
 - The root does not expose an obvious global formatting tool (no Spotless or root Checkstyle detected). Use the existing code style. Run `./gradlew check` to execute configured verification tasks.
 
+Collections optimization pattern
+- In collection implementations (dictionaries, arrays), use early-exit `isEmpty()` checks to avoid unnecessary allocations and iterations. Return empty collections or unmodified containers immediately when the collection is empty.
+- Example: Check `isEmpty()` before allocating arrays in `keys()`, `values()`, or `iterator()` methods; return `IntArray.empty()`, `Array.empty(type)`, or unmodified containers on empty state.
+- This applies across all collection types: `IntToRef`, `LongToRef`, `RefToRef` dictionaries, and array implementations.
+
 Testing conventions
 - Use AssertJ for assertions (import `org.assertj.core.api.Assertions`), not JUnit's `Assertions`.
 - Test class naming: `<ClassName>Test.java` in the same package under `src/test/java`.
@@ -68,7 +73,7 @@ Testing conventions
 
 Javadoc conventions
 - All public classes, interfaces, and methods should have javadoc.
-- Javadoc must include `@since` tag with version (e.g., `@since 10.0.0`).
+- Javadoc must include `@since` tag with version (e.g., `@since 10.0.0`). Use the base GA version, not pre-release qualifiers (e.g., use `10.0.0` not `10.0.alpha14`), even if `build.gradle` specifies a pre-release version.
 - Use short, active-voice descriptions (e.g., "Returns an array" not "Return an array").
 - Do not use trailing periods in `@param` and `@return` descriptions (e.g., `@param value the value` not `@param value the value.`).
 - Include `@param` and `@return` tags for non-trivial methods.

.github/skills/generate-branch-summary.md

@@ -0,0 +1,163 @@
+# Skill: Generate Branch Summary
+
+## Purpose
+Generate a concise, structured summary of all changes in the current branch compared to the develop branch. This summary is written to `summary.md` and serves as the single source of truth for understanding what a branch introduces.
+
+## When to Use
+- After completing implementation work on a feature branch
+- Before opening a pull request to develop
+- When updating branch documentation
+- To communicate changes clearly to reviewers
+
+## Process
+
+### 1. Determine Current Branch Context
+```bash
+git rev-parse --abbrev-ref HEAD  # Get current branch name
+git log --oneline -5              # Check recent commits
+```
+
+### 2. Analyze Changes Relative to Develop
+```bash
+git diff --stat develop...HEAD    # Summary of changed files
+git log --oneline develop..HEAD   # Commits in this branch
+git --no-pager diff develop...HEAD # Full diff (use --no-pager to avoid pager issues)
+```
+
+### 3. Categorize Changes
+Group modifications by their nature:
+- **New APIs/Features** — new interfaces, classes, methods
+- **Performance Optimizations** — efficiency improvements, early-exit checks, reduced allocations
+- **Bug Fixes** — corrections to existing behavior
+- **Refactoring** — internal improvements without behavior change
+- **Documentation** — javadoc, comments, instruction files, style guides
+- **Version Bumps** — changes to version numbers in build.gradle or other config
+
+### 4. Structure the Summary
+Create a section in `summary.md` with this format:
+
+```markdown
+# Branch: <branch-name>
+
+**Status:** <Ready for review / In progress / Draft>
+**Commits:** <number> (e.g., "1 (abc1234 - 'commit message')" or "3 commits")
+**Version:** <old-version> → <new-version> (if applicable)
+
+## Changes Summary
+
+### <Category 1> (e.g., "New Array API")
+- Description of what was added/changed
+- Key implementation details
+- Important behaviors or constraints
+
+### <Category 2> (e.g., "Collection Optimization Pattern")
+- Explanation of the optimization
+- Which files/classes affected
+- Methods modified (count if many)
+
+### <Category 3> (e.g., "Documentation")
+- What documentation was added
+- Why it matters (e.g., for future contributors)
+
+## Testing & Validation
+- `./gradlew :module-name:build` ✅
+- `./gradlew clean build` (recommended before merge)
+```
+
+### 5. Key Guidelines for Content
+
+#### Be Specific
+- ✅ "Added `tryTrimTo(int)` method to safely resize internal storage"
+- ❌ "Added new method"
+
+#### Quantify When Helpful
+- ✅ "Applied isEmpty() checks to 21 methods across 3 dictionary types"
+- ❌ "Applied optimization across dictionaries"
+
+#### Explain Impact
+- ✅ "Avoids unnecessary allocations and iterations when collections are empty"
+- ❌ "Performance improvement"
+
+#### Include Implementation Details
+- ✅ "Returns unchanged if requested size exceeds capacity or is less than current size"
+- ❌ "Has validation logic"
+
+#### Use Clear Formatting
+- Use markdown headers (`#`, `##`, `###`) for hierarchy
+- Use bullet points for lists
+- Use bold (`**`) for emphasis on key terms
+- Use inline code (`` ` ` ``) for class/method names
+
+### 6. Output Location
+Always write to `summary.md` in the repository root, replacing or updating the previous summary section.
+
+### 7. Keep Previous Content
+If `summary.md` already contains unrelated sections (e.g., documentation of other work), preserve them unless explicitly asked to remove them. Only update or replace the branch summary section.
+
+## Example Output
+
+```markdown
+# Branch: update-api-part-2
+
+**Status:** Ready for review  
+**Commits:** 1 (1367d9b - "small improvements")  
+**Version:** 10.0.alpha13 → 10.0.alpha14
+
+## Changes Summary
+
+### 1. New Array API: `tryTrimTo(int)`
+- Added `UnsafeMutableArray.tryTrimTo(int internalStorageSize)` method for safe internal storage resizing
+- Implemented in `AbstractMutableArray` with validation:
+  - Returns unchanged if requested size exceeds current capacity
+  - Returns unchanged if requested size is less than current element count
+  - Performs trimming for valid requests
+- Includes complete javadoc with `@since 10.0.alpha14` tag
+
+### 2. Collection Optimization Pattern
+Applied early-exit `isEmpty()` checks across dictionary implementations:
+- **AbstractHashBasedIntToRefDictionary:** 7 methods optimized
+- **AbstractHashBasedLongToRefDictionary:** 7 methods optimized
+- **AbstractHashBasedRefToRefDictionary:** 7 methods optimized
+
+Optimized methods: `iterator()`, `keys()` (all overloads), `values()` (all overloads)  
+**Benefit:** Avoids allocations and iterations when collections are empty
+
+### 3. Documentation
+- Added comprehensive javadoc to `tryTrimTo()` method
+- Updated `.github/copilot-instructions.md` with "Collections optimization pattern" section
+
+## Testing & Validation
+- Module build: `./gradlew :rlib-collections:build` ✅
+- Full build verification: `./gradlew clean build` (recommended before merge)
+```
+
+## Common Patterns in RLib
+
+### API Additions
+Always mention:
+- Method signature and purpose
+- Return type and parameter descriptions
+- Javadoc status (whether included, version tag)
+- Key behaviors or constraints
+
+### Optimizations
+Always mention:
+- What was optimized (method names, counts)
+- Why (avoid allocations, reduce iterations, etc.)
+- Affected files/classes
+- Observable impact
+
+### Documentation Changes
+Mention:
+- What was added or updated
+- Why it matters (helps future contributors, clarifies usage, standardizes conventions)
+- Files affected
+
+## Tips
+
+1. **Use `git diff --stat`** to get a quick overview of which files changed and how many lines
+2. **Use `git log develop..HEAD`** to list all commits in the branch for reference
+3. **Extract key insights from the actual diff** — skim the output to understand the nature of changes
+4. **Be concise** — summaries should be readable in 2-3 minutes
+5. **Link to code** — mention file paths and method names so reviewers can navigate easily
+6. **Quantify changes** — "7 methods optimized" is more informative than "several optimizations"

README.md

@@ -45,7 +45,7 @@ repositories {
 }
 
 ext {
-    rlibVersion = "10.0.alpha13"
+    rlibVersion = "10.0.alpha14"
 }
 
 dependencies {

build.gradle

@@ -1,4 +1,4 @@
-rootProject.version = "10.0.alpha13"
+rootProject.version = "10.0.alpha14"
 group = 'javasabr.rlib'
 
 allprojects {

rlib-collections/src/main/java/javasabr/rlib/collections/array/UnsafeMutableArray.java

@@ -53,4 +53,16 @@ public interface UnsafeMutableArray<E> extends UnsafeArray<E>, MutableArray<E> {
    * @since 10.0.0
    */
   UnsafeMutableArray<E> trimToSize();
+
+  /**
+   * Attempts to trim the internal storage to the specified size.
+   *
+   * If the requested size is greater than the current capacity or less than the
+   * current size, the array is not modified.
+   *
+   * @param internalStorageSize the desired internal storage size
+   * @return this for method chaining
+   * @since 10.0.0
+   */
+  UnsafeMutableArray<E> tryTrimTo(int internalStorageSize);
 }

rlib-collections/src/main/java/javasabr/rlib/collections/array/impl/AbstractMutableArray.java

@@ -214,14 +214,26 @@ public UnsafeMutableArray<E> prepareForSize(int expectedSize) {
   public UnsafeMutableArray<E> trimToSize() {
     @Nullable E[] wrapped = wrapped();
     int size = size();
-
     if (size == wrapped.length) {
       return this;
     }
     wrapped(Arrays.copyOfRange(wrapped, 0, size));
     return this;
   }
 
+  @Override
+  public UnsafeMutableArray<E> tryTrimTo(int internalStorageSize) {
+    @Nullable E[] wrapped = wrapped();
+    int size = size();
+    if (internalStorageSize >= wrapped.length) {
+      return this;
+    } else if (internalStorageSize < size) {
+      return this;
+    }
+    wrapped(Arrays.copyOf(wrapped, internalStorageSize));
+    return this;
+  }
+
   @Override
   public UnsafeMutableArray<E> asUnsafe() {
     return this;

rlib-collections/src/main/java/javasabr/rlib/collections/dictionary/impl/AbstractHashBasedIntToRefDictionary.java

@@ -85,8 +85,9 @@ public Optional<V> getOptional(int key) {
   public Iterator<V> iterator() {
     if (isEmpty()) {
       return Collections.emptyIterator();
+    } else {
+      return new LinkedRefEntryIterator<>(entries());
     }
-    return new LinkedRefEntryIterator<>(entries());
   }
 
   @Nullable
@@ -118,48 +119,59 @@ public void forEach(IntObjConsumer<V> consumer) {
 
   @Override
   public IntArray keys() {
-    return IntArray.copyOf(keys(ArrayFactory.mutableIntArray()));
+    if (isEmpty()) {
+      return IntArray.empty();
+    } else {
+      return IntArray.copyOf(keys(ArrayFactory.mutableIntArray()));
+    }
   }
 
   @Override
   public MutableIntArray keys(MutableIntArray container) {
-
+    if (isEmpty()) {
+      return container;
+    }
     UnsafeMutableIntArray unsafe = container.asUnsafe();
     unsafe.prepareForSize(container.size() + size());
-
     for (E entry : entries()) {
       while (entry != null) {
         unsafe.unsafeAdd(entry.key());
         entry = entry.next();
       }
     }
-
     return container;
   }
 
   @Override
   public Array<Integer> keys(Class<Integer> type) {
-    return keys(MutableArray.ofType(Integer.class));
+    if (isEmpty()) {
+      return Array.empty(type);
+    } else {
+      return keys(MutableArray.ofType(type));
+    }
   }
 
   @Override
   public MutableArray<Integer> keys(MutableArray<Integer> container) {
-
+    if (isEmpty()) {
+      return container;
+    }
     UnsafeMutableArray<Integer> unsafe = container.asUnsafe();
     unsafe.prepareForSize(container.size() + size());
-
     for (E entry : entries()) {
       while (entry != null) {
         unsafe.unsafeAdd(entry.key());
         entry = entry.next();
       }
     }
-
     return container;
   }
 
   @Override
   public <C extends Collection<Integer>> C keys(C container) {
+    if (isEmpty()) {
+      return container;
+    }
     for (E entry : entries()) {
       while (entry != null) {
         container.add(entry.key());
@@ -171,11 +183,18 @@ public <C extends Collection<Integer>> C keys(C container) {
 
   @Override
   public Array<V> values(Class<V> type) {
-    return Array.copyOf(values(ArrayFactory.mutableArray(type, size())));
+    if (isEmpty()) {
+      return Array.empty(type);
+    } else {
+      return Array.copyOf(values(ArrayFactory.mutableArray(type, size())));
+    }
   }
 
   @Override
   public <C extends Collection<V>> C values(C container) {
+    if (isEmpty()) {
+      return container;
+    }
     for (E entry : entries()) {
       while (entry != null) {
         V value = entry.value();
@@ -190,10 +209,11 @@ public <C extends Collection<V>> C values(C container) {
 
   @Override
   public MutableArray<V> values(MutableArray<V> container) {
-
+    if (isEmpty()) {
+      return container;
+    }
     UnsafeMutableArray<V> unsafe = container.asUnsafe();
     unsafe.prepareForSize(container.size() + size());
-
     for (E entry : entries()) {
       while (entry != null) {
         V value = entry.value();
@@ -203,7 +223,6 @@ public MutableArray<V> values(MutableArray<V> container) {
         entry = entry.next();
       }
     }
-
     return container;
   }
 }