LangChain4j

LangChain4j is a Java library that provides a unified API for integrating LLMs and vector stores into applications running on the Java Virtual Machine.

LangChain4j is an open-source library designed to connect Java applications with Large Language Models and vector databases. It provides a unified API to access various commercial and open-source models, enabling the development of chatbots and AI assistants. The library offers specific integrations for frameworks like Quarkus, Spring Boot, and Helidon. It supports two-way interaction, allowing Java code to invoke LLMs and LLMs to call Java functions. Developers use it for prompt templating, memory management, output parsing, and implementing patterns such as Agents and Retrieval Augmented Generation.

LangChain4j at a glance

Best for: Software engineer
Runs on: open source
Pricing: Free
Released: June 2023
Category: AI coding tool
Website: docs.langchain4j.dev

Key features

Unified API for major LLMs and vector stores
Integration support for Quarkus, Spring Boot, and Helidon
Two-way interaction between Java code and LLMs
Tools for prompt templating and output parsing
Chat memory management
High-level support for Agents and RAG patterns

Use it for

Building AI-powered chatbots
Creating virtual assistants
Implementing Retrieval Augmented Generation (RAG) pipelines
Developing LLM-based agents with tool access

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