chore: Convert data types to Kotlin by dkhawk · Pull Request #1578 · googlemaps/android-maps-utils

dkhawk · 2025-08-29T22:28:08Z

This pull request refactors several core data classes from Java to Kotlin. This modernization improves code readability, safety, and conciseness by leveraging Kotlin features like properties, val, and non-nullable types.

Summary of Changes

DataPolygon.java -> DataPolygon.kt: Converted the DataPolygon interface to Kotlin. It now uses val properties for outerBoundaryCoordinates and innerBoundaryCoordinates.
Feature.java -> Feature.kt: Converted the Feature class to Kotlin. This includes:
- Replacing Java getters and setters (getGeometry, getProperties, hasProperty) with Kotlin properties (geometry, properties, hasProperty).
- Using a private backing property (_properties) for the mutable map to expose an immutable view.
Geometry.java -> Geometry.kt: Converted the Geometry interface to Kotlin, using val properties for geometryType and geometryObject.
Layer.java -> Layer.kt: Converted the Layer abstract class to Kotlin. It now uses generic types for Feature and uses Kotlin's property access syntax for renderer (renderer.map instead of renderer.getMap()).
LineString.java -> LineString.kt: Converted the LineString class to Kotlin, using val properties for its data and adding equals and hashCode implementations.
MultiGeometry.java -> MultiGeometry.kt: Converted the MultiGeometry class to Kotlin. The constructor now enforces non-nullability, and the getGeometryType method is replaced with an override property.
Point.java -> Point.kt: Converted the Point class to Kotlin, using val properties for its data and including equals, hashCode, and toString overrides.

googlemaps-bot · 2025-08-29T22:34:41Z

Code Coverage

Overall Project	40.52% `-0.69%`	🍏
Files changed	84.04%	🍏

File	Coverage
GeoJsonMultiPoint.java	100%	🍏
GeoJsonMultiPolygon.java	100%	🍏
GeoJsonGeometryCollection.java	100%	🍏
GeoJsonMultiLineString.java	100%	🍏
SphericalUtil.kt	99.72%	🍏
PolyUtil.kt	97.88% `-0.07%`	🍏
Point.kt	93.75% `-6.25%`	🍏
Feature.kt	91.38% `-8.62%`	🍏
LineString.kt	89.06% `-10.94%`	🍏
MultiGeometry.kt	72% `-28%`	🍏
Layer.kt	69.23% `-30%`	🍏
GeoJsonFeature.java	60.09% `-3.29%`	❌
KmlPolygon.java	53.52%	🍏
GeoJsonLayer.java	42.11%	🍏
KmlMultiGeometry.java	38.89%	🍏
GeoJsonRenderer.java	35.68% `-13.51%`	❌
Renderer.java	16.74%	🍏
KmlRenderer.java	3.13% `-3.23%`	❌
KmlLayer.java	0% `-1.24%`	❌

This commit modernizes the `Point` class by converting it from Java to idiomatic Kotlin, improving null safety, readability, and code conciseness. The corresponding tests have also been migrated and improved. Key changes: - **Port `Point` to Kotlin**: The `Point` data class has been converted to Kotlin, leveraging its features for a more robust implementation. - **Migrate and Enhance `PointTest`**: The `PointTest` class is now in Kotlin and uses the Google Truth assertion library for more expressive tests. - **Improved Test Coverage**: New tests for `equals()`, `hashCode()`, and `toString()` have been added. The nullability test was updated to use reflection to verify Java interoperability, confirming that a `NullPointerException` is thrown for null constructor arguments. - **Update `GeoJsonPointTest`**: A related test was updated to expect a `NullPointerException` instead of an `IllegalArgumentException`, aligning with the behavior of the new Kotlin-based `Point` superclass. - **Update Copyright Headers**: Copyright years were updated in the modified files.

This commit modernizes the `LineString` class and its corresponding tests by converting them from Java to idiomatic Kotlin. This change improves code conciseness, readability, and null safety. The key changes are: - **Port `LineString` to Kotlin**: The `LineString` class has been completely rewritten in Kotlin. - **Port `LineStringTest` to Kotlin**: The test class for `LineString` has been converted to Kotlin and updated to use Google Truth for assertions, making the tests more expressive. - **Enhance Test Coverage**: Added tests for `equals()`, `hashCode()`, and `toString()` to ensure correctness. - **Update Related Tests**: The `GeoJsonLineStringTest` was updated to catch `NullPointerException` instead of `IllegalArgumentException`, reflecting the stricter null-safety of the new Kotlin-based `LineString` constructor.

This commit refactors the `DataPolygon` interface from Java to Kotlin. Key changes: - The `DataPolygon` interface is now a Kotlin file, with `get...()` methods converted to idiomatic Kotlin properties. - `KmlPolygon` has been updated to use the `List` interface instead of the concrete `ArrayList` in its implementation of `DataPolygon`. - The copyright year has been updated in `DataPolygon.kt`.

This commit modernizes the `Feature` class by porting it from Java to idiomatic Kotlin, improving its conciseness, readability, and null safety. The key changes include: - **Porting `Feature` to Kotlin**: The class is now written in Kotlin, using modern language features like properties and a primary constructor. - **Correct Observable Behavior**: Setters for geometry and properties now correctly call `setChanged()` and `notifyObservers()`, ensuring that observers are notified of modifications. - **Test Modernization**: The corresponding `FeatureTest` has been ported to Kotlin and now uses Google Truth for more expressive assertions. - **Enhanced Test Coverage**: New tests have been added to verify the `Observable` behavior when a feature's properties or geometry are changed. - **Subclass Update**: `GeoJsonFeature` has been updated to align with the changes in its `Feature` superclass.

This commit refactors the `Geometry` interface, converting it from Java to Kotlin. As part of this change, the `getGeometryType()` and `getGeometryObject()` methods have been replaced with the idiomatic Kotlin properties `geometryType` and `geometryObject`. The implementing classes, `Point` and `LineString`, and their corresponding tests have been updated to align with this new property-based API.

This commit refactors the `Layer` class by converting it from Java to idiomatic Kotlin. It also introduces generics to both the `Layer` and `Renderer` classes to improve type safety throughout the data layer. Key changes: - **Convert `Layer` to Kotlin**: The `Layer` class is now `Layer.kt`, utilizing Kotlin features like properties and `when` expressions for more concise and readable code. - **Introduce Generics**: `Layer` and `Renderer` are now generic (`Layer<T : Feature>`, `Renderer<T extends Feature>`). This enforces type constraints at compile time. - **Improve Type Safety**: Subclasses like `GeoJsonLayer`, `KmlLayer`, `GeoJsonRenderer`, and `KmlRenderer` now extend the generic base classes, eliminating the need for unsafe casts when handling features. - **Add Unit Tests**: A new `LayerTest.kt` file has been added with comprehensive unit tests for the `Layer` class, using MockK and Truth to verify its behavior.

This commit refactors the `MultiGeometry` class from Java to Kotlin, improving its design, null safety, and immutability. The key changes are: - **Porting `MultiGeometry` to Kotlin**: The class is now a generic, immutable Kotlin class. The constructor enforces non-nullability for the list of geometries, changing the exception for null constructor arguments from `IllegalArgumentException` to `NullPointerException`. - **Updating Subclasses**: All subclasses of `MultiGeometry` (e.g., `GeoJsonMultiPoint`, `KmlMultiGeometry`) have been updated to align with the new Kotlin base class. They now override the `geometryType` property instead of calling a setter. - **Modernizing Tests**: The `MultiGeometryTest` has been converted to Kotlin and uses Google Truth. Tests for all affected subclasses have been updated to assert the correct exception types.

This commit introduces `Polyline` and `Polygon` as type aliases for `List<LatLng>` to improve code readability and provide stronger semantic meaning. This change makes it explicit whether a list of coordinates represents a line or a closed area. The following files and classes have been updated to use these new type aliases: - `PolyUtil`: Functions now accept `Polyline` or `Polygon` instead of a generic `List<LatLng>`. - `SphericalUtil`: `computeLength` and `computeArea` now operate on `Polyline` and `Polygon` respectively. - `LineString`: The `coordinates` property is now of type `Polyline`. - `DataPolygon`: Boundary properties now use the `Polygon` type alias.

This commit refactors the `SphericalUtil` object to improve code clarity and leverage modern Kotlin features. Key changes include: - Introduced private `toRadians()` and `toDegrees()` extension functions for `Double` to replace calls to `Math.toRadians()` and `Math.toDegrees()`. - Converted several methods to more concise single-expression functions. - Improved the readability of the `computeHeading` function by using more descriptive variable names and clearer logic.

This commit refactors the `SphericalUtil` object to use more modern and idiomatic Kotlin patterns, improving code readability and conciseness. Key changes include: - **Functional Approach**: Replaced imperative `for` loops in `computeLength` and `computeSignedArea` with functional constructs like `zipWithNext()` and `sumOf()`. - **Extension Functions**: Introduced helper extension functions for `LatLng` to enable destructuring (`component1`/`component2`) and simplify conversion to radians (`toRadians`). - **Code Cleanup**: Refactored methods like `computeOffset`, `computeOffsetOrigin`, and `interpolate` to use immutable variables (`val`) and the new helper functions. - **New Tests**: Added `SphericalUtilKotlinTest.kt` to provide test coverage for the refactored list-based calculations using Google Truth.

This commit refactors the `computeSignedArea` function for better performance and readability. The implementation now uses a `Sequence` to iterate over the path edges, avoiding the allocation of an intermediate list for the closed path. A local function, `polarArea`, has also been introduced to improve code clarity.

This commit includes minor code cleanup across several files: - Removes extra newlines in `GeoJson*`, and `Layer` classes. - Fixes indentation in `PolyUtil`. - Improves readability in `SphericalUtil.computeSignedArea`

kikoso · 2025-09-15T16:46:32Z

library/src/main/java/com/google/maps/android/data/LineString.kt

@@ -0,0 +1,61 @@
+/*


Some classes are being marked as moved, some others as new classes. I wonder if we could unify this (ideally, with files being marked as moved)

kikoso · 2025-09-15T16:47:24Z

library/src/main/java/com/google/maps/android/data/MultiGeometry.kt

+    override fun toString(): String {
+        val geometries = "geometries=$geometryObject"
+        return "MultiGeometry{$geometries}"
+    }


Would we like to have a hashCode() function here?

kikoso · 2025-09-15T16:50:22Z

library/src/main/java/com/google/maps/android/data/geojson/GeoJsonGeometryCollection.java

-     */
-    public String getType() {
-        return getGeometryType();
+    @Override


This would introduce a breaking change. It is probably fine when we are done with the migration, but for now we can add it as a new function and deprecate the previous one. What do you think?

kikoso · 2025-09-15T16:50:44Z

library/src/main/java/com/google/maps/android/data/geojson/GeoJsonMultiLineString.java

-     */
-    public String getType() {
-        return getGeometryType();
+    @Override


Same issue with the breaking change.

kikoso · 2025-09-15T17:28:13Z

library/src/main/java/com/google/maps/android/data/Geometry.kt

+/**
+ * A Polygon is a list of LatLngs where each LatLng is a vertex of the polygon.
+ */
+typealias Polygon = List<LatLng>


I was about to write that we had a breaking change, and whether we could consider an alias. Well done!

dkhawk changed the title ~~Feat/port data package to kotlin~~ chore: Convert data types to Kotlin Aug 29, 2025

dkhawk requested a review from kikoso August 29, 2025 22:39

dkhawk added 17 commits September 5, 2025 14:37

Rename .java to .kt

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Rename .java to .kt

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Rename .java to .kt

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Rename .java to .kt

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Rename .java to .kt

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dkhawk force-pushed the feat/port-data-package-to-kotlin branch from 55bea6a to 3148633 Compare September 5, 2025 22:52

dkhawk added 2 commits September 5, 2025 17:27

refactor: Minor code style and readability improvements

9936fae

This commit includes minor code cleanup across several files: - Removes extra newlines in `GeoJson*`, and `Layer` classes. - Fixes indentation in `PolyUtil`. - Improves readability in `SphericalUtil.computeSignedArea`

kikoso reviewed Sep 15, 2025

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dkhawk marked this pull request as draft September 16, 2025 19:53

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chore: Convert data types to Kotlin#1578

chore: Convert data types to Kotlin#1578
dkhawk wants to merge 19 commits intomainfrom
feat/port-data-package-to-kotlin

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