Add Java select-algorithm sample

ai/select-algorithm-java/.gitignore

@@ -0,0 +1,12 @@
+# Build output
+target/
+
+# IDE
+.idea/
+*.iml
+.classpath
+.project
+.settings/
+
+# Environment
+.env

ai/select-algorithm-java/README.md

@@ -0,0 +1,107 @@
+# DocumentDB Vector Index Algorithm Comparison (Java)
+
+This sample compares DocumentDB vector index algorithms (DiskANN, HNSW, IVF) across similarity functions (COS, L2, IP) to help you choose the best configuration for your use case.
+
+## Overview
+
+Vector indexes improve search performance by organizing vectors for efficient similarity searches. This sample:
+
+- Creates collections per algorithm/similarity combination
+- Configures algorithm-specific index parameters
+- Measures query latency for each configuration
+- Displays a comparison table to guide your selection
+
+## Prerequisites
+
+- [Java 21 or higher](https://learn.microsoft.com/java/openjdk/download)
+- [Maven 3.6 or higher](https://maven.apache.org/download.cgi)
+- [Azure CLI](https://learn.microsoft.com/cli/azure/install-azure-cli)
+- Azure subscription with:
+  - Azure DocumentDB (MongoDB vCore) cluster
+  - Azure OpenAI with text-embedding-3-small model
+  - Managed identity configured for passwordless auth
+
+## Setup
+
+1. Copy `.env.example` to `.env`:
+   ```bash
+   cp .env.example .env
+   ```
+
+2. Update `.env` with your Azure resource values. The sample uses the
+   [dotenv-java](https://github.com/cdimascio/dotenv-java) library to load
+   variables from `.env` at startup, falling back to system environment
+   variables when the file is absent.
+
+3. Sign in to Azure for passwordless authentication:
+   ```bash
+   az login
+   ```
+
+4. Compile the project:
+   ```bash
+   mvn clean compile
+   ```
+
+> **Note:** This sample does not include a Maven Wrapper (`mvnw`). Install
+> Maven 3.6+ from <https://maven.apache.org/download.cgi> and ensure `mvn` is
+> on your PATH.
+
+## Usage
+
+Run the comparison for specific or all algorithms and similarity functions:
+
+```bash
+# Compare all algorithms with cosine similarity
+mvn exec:java -Dexec.mainClass="com.azure.documentdb.selectalgorithm.SelectAlgorithm"
+
+# Compare only DiskANN with all similarity functions
+ALGORITHM=diskann SIMILARITY=all mvn exec:java -Dexec.mainClass="com.azure.documentdb.selectalgorithm.SelectAlgorithm"
+
+# Compare HNSW with L2 (Euclidean) distance
+ALGORITHM=hnsw SIMILARITY=L2 mvn exec:java -Dexec.mainClass="com.azure.documentdb.selectalgorithm.SelectAlgorithm"
+
+# Compare all algorithms and all similarity functions
+ALGORITHM=all SIMILARITY=all mvn exec:java -Dexec.mainClass="com.azure.documentdb.selectalgorithm.SelectAlgorithm"
+```
+
+### Environment Variables
+
+- `ALGORITHM`: Which algorithm(s) to test
+  - `all` (default): Test DiskANN, HNSW, and IVF
+  - `diskann`: Test only DiskANN
+  - `hnsw`: Test only HNSW
+  - `ivf`: Test only IVF
+
+- `SIMILARITY`: Which similarity function(s) to test
+  - `COS` (default): Cosine similarity
+  - `L2`: Euclidean distance
+  - `IP`: Inner product
+  - `all`: Test all similarity functions
+
+## Algorithm Characteristics
+
+### DiskANN
+- Disk-based for large datasets
+- Good balance of speed and accuracy
+- Parameters: maxDegree=32, lBuild=50, lSearch=100
+
+### HNSW
+- Memory-based hierarchical graph
+- Excellent for real-time applications
+- Parameters: m=16, efConstruction=64, efSearch=80
+
+### IVF
+- Cluster-based partitioning
+- Fast search via centroids
+- Parameters: numLists=1, nProbes=1
+
+## Output
+
+The sample prints a comparison table showing latency per query for each algorithm/similarity combination, helping you make an informed choice.
+
+## Further Resources
+
+- [Azure DocumentDB Documentation](https://learn.microsoft.com/azure/documentdb/)
+- [Vector Search in DocumentDB](https://learn.microsoft.com/azure/documentdb/vector-search)
+- [MongoDB Java Driver Documentation](https://mongodb.github.io/mongo-java-driver/)

ai/select-algorithm-java/pom.xml

@@ -0,0 +1,78 @@
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+
+    <groupId>com.azure.documentdb.samples</groupId>
+    <artifactId>select-algorithm-java</artifactId>
+    <version>1.0-SNAPSHOT</version>
+    <name>Azure DocumentDB Vector Algorithm Comparison</name>
+    <description>Compare DocumentDB vector index algorithms (DiskANN, HNSW, IVF) using Java SDK</description>
+
+    <properties>
+        <maven.compiler.source>21</maven.compiler.source>
+        <maven.compiler.target>21</maven.compiler.target>
+        <maven.compiler.release>21</maven.compiler.release>
+        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+    </properties>
+
+    <dependencyManagement>
+        <dependencies>
+            <dependency>
+                <groupId>com.azure</groupId>
+                <artifactId>azure-sdk-bom</artifactId>
+                <version>1.2.29</version>
+                <type>pom</type>
+                <scope>import</scope>
+            </dependency>
+        </dependencies>
+    </dependencyManagement>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.mongodb</groupId>
+            <artifactId>mongodb-driver-sync</artifactId>
+            <version>5.6.2</version>
+        </dependency>
+        <dependency>
+            <groupId>com.azure</groupId>
+            <artifactId>azure-identity</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>com.azure</groupId>
+            <artifactId>azure-ai-openai</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>com.fasterxml.jackson.core</groupId>
+            <artifactId>jackson-databind</artifactId>
+            <version>2.18.2</version>
+        </dependency>
+        <dependency>
+            <groupId>io.github.cdimascio</groupId>
+            <artifactId>dotenv-java</artifactId>
+            <version>3.0.2</version>
+        </dependency>
+        <dependency>
+            <groupId>org.slf4j</groupId>
+            <artifactId>slf4j-simple</artifactId>
+            <version>2.0.17</version>
+            <scope>runtime</scope>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <version>3.13.0</version>
+                <configuration>
+                    <release>21</release>
+                    <compilerArgs>
+                        <arg>-Xlint:all</arg>
+                    </compilerArgs>
+                </configuration>
+            </plugin>
+        </plugins>
+    </build>
+</project>