Implementation:Ray project Ray Ray Init

Knowledge Sources	Ray Ray Java API
Domains	Distributed_Computing, Runtime_Management
Last Updated	2026-02-13 17:00 GMT

Overview

Concrete tool for bootstrapping the Ray distributed runtime provided by the Ray Java SDK.

Description

The Ray.init() static method initializes the Ray runtime by loading the DefaultRayRuntimeFactory via reflection, creating a RayRuntime instance, and registering a JVM shutdown hook that calls Ray.shutdown(). After initialization, the static Ray.runtime field holds the active runtime, and all subsequent Ray.task(), Ray.actor(), Ray.put(), and Ray.get() calls are dispatched through it.

Usage

Call Ray.init() at the start of any Java application that uses Ray. It must be invoked before any distributed operations. It is safe to call from the main thread; the method is synchronized and idempotent.

Code Reference

Source Location

• Repository: ray-project/ray
• File: java/api/src/main/java/io/ray/api/Ray.java
• Lines: L15-34

Signature

public static void init()

The private overload:

private static synchronized void init(RayRuntimeFactory factory)

Import

import io.ray.api.Ray;

I/O Contract

Inputs

Name	Type	Required	Description
(none)	—	—	Zero-argument method. Optionally reads system property ray.job.code-search-path and ray.conf config file.

Outputs

Name	Type	Description
Ray.runtime	RayRuntime	Static field set to the initialized runtime instance
Shutdown hook	Thread	JVM shutdown hook registered via Runtime.addShutdownHook

Usage Examples

Basic Initialization

import io.ray.api.Ray;
import io.ray.api.ObjectRef;

public class MyApp {
    public static int square(int x) {
        return x * x;
    }

    public static void main(String[] args) {
        // 1. Initialize Ray runtime
        Ray.init();

        // 2. Submit a remote task
        ObjectRef<Integer> result = Ray.task(MyApp::square, 5).remote();

        // 3. Retrieve the result
        int value = result.get();
        System.out.println("Result: " + value); // 25

        // 4. Shutdown
        Ray.shutdown();
    }
}

Related Pages

Implements Principle

• Principle:Ray_project_Ray_Ray_Runtime_Initialization

Requires Environment

• Environment:Ray_project_Ray_Java_Build_Environment