# Installation

> USearch for Java

Gradle is the recommended route, since Maven Central does not carry the native builds; this Groovy script downloads a "fat JAR" carrying builds for Linux, Windows, macOS, and Android:

```groovy
repositories {
    mavenCentral()
    flatDir { dirs 'lib' }
}

task downloadUSearchJar {
    doLast {
        def usearchVersion = '3.0.0'
        def usearchUrl = "https://github.com/unum-cloud/USearch/releases/download/v${usearchVersion}/usearch-${usearchVersion}.jar"
        def usearchFile = file("lib/usearch-${usearchVersion}.jar")
        usearchFile.parentFile.mkdirs()
        if (!usearchFile.exists()) {
            new URL(usearchUrl).withInputStream { source -> usearchFile.withOutputStream { it << source } }
}
}
}

compileJava.dependsOn downloadUSearchJar

dependencies {
    implementation name: 'usearch', version: '3.0.0', ext: 'jar'
}
```

Gradle drives CMake for the engine, so building from source needs nothing else, and `-PusearchPrebuilt` points the suites at an engine CMake already built:

```sh
gradle clean build                                    # engine, SDK, and the Java, Kotlin and Scala suites
gradle -PusearchPrebuilt=$PWD/build_release test      # against a library built beforehand
```

The SDK looks for the shared object on the system library path first, which a locally built tree offers, and otherwise extracts the platform's copy packaged inside the JAR to a temporary directory.

### Source Layout & Imports

One source file mirrors one header.
`Types.java` carries the shared vocabulary: `Key`, `Status`, `Scalar`, `Residency`, `Traversal`, `Executor`, `Arena`, `Mood`, `Deferred`, `USearchException`, `RowsView`, and the arena-backed `Matches` and `Monolith`.
`DenseIndex.java` carries the dense modality: the index itself, its `On` and `DeferredOn` receivers, `DenseOptions`, `DenseMetric`, `DenseMetadata`, `DenseIndexDescription`, `DenseReachability`, `DenseTraversalStats`, the `Dense*Config` knobs, `ValueLookup`, the arena-backed `DenseVectors`, `DenseProducts` and `DenseBatch`, and the `DenseCursor` and `DenseSearchStream` scans.
`DenseVerbs.java` writes the blocking verbs once for the index and its `On` receiver.
`Library.java` loads the shared object and links every verb against it.
Both vocabularies are nested types, and a nested type imports directly, so every call site below spells the bare name:

```java
import cloud.unum.usearch.DenseIndex;
import cloud.unum.usearch.DenseIndex.DenseMetric;
import cloud.unum.usearch.DenseIndex.DenseOptions;
import cloud.unum.usearch.DenseIndex.DenseSearchConfig;
import cloud.unum.usearch.Types.Arena;
import cloud.unum.usearch.Types.Deferred;
import cloud.unum.usearch.Types.Executor;
import cloud.unum.usearch.Types.Key;
import cloud.unum.usearch.Types.Matches;
import cloud.unum.usearch.Types.RowsView;
import cloud.unum.usearch.Types.Scalar;
```