# Building AI Agents with ADK for Java

> Master building AI agents in Java with Google's ADK, exploring setup, debugging via Dev UI, powerful tools, multi-agent systems, and advanced features.

Author: [Guillaume Laforge](https://glaforge.dev/) | Published: 2025-10-22 | Topics: ai-agents, java, agent-development-kit | Canonical: https://glaforge.dev/talks/2025/10/22/building-ai-agents-with-adk-for-java/


At Devoxx Belgium, I recently had the chance to present this new talk dedicated to
[ADK for Java](https://google.github.io/adk-docs/),
the open source Agent Development Kit framework developed by Google.

The presentation covered:

- an introduction to the notion of AI agents
- how to **get started in a Java and Maven project**
- how to create your first agent
- how to debug an agent via the **Dev UI**
- the coverage of the various **tools** (custom function tools, built-in tools like Google Search or code execution, an agent as tool, MCP tools)
- an overview of the different ways to combine agents into a **multi-agent system**: sub-agents, sequential agents, parallel agents, loop agents
- some details on the **event loop** and services (session and state management, artifacts, runner...)
- **structured** input / output schemas
- the various **callbacks** in the agent lifecycle
- the integration with LangChain4j (to give access to the plethora of LLMs supported by LangChain4j)
- the definition of agents via **configuration in YAML**
- the new **long-term memory** support
- the **plugin** system
- the new external **code executors** (via Docker containers or backed by Google Cloud Vertex AI)
- how to launch an agent with the Dev UI from **JBang**

## Slides of the presentation

The slide deck of this session is embedded below:

{{< speakerdeck 1cd42280a265486396c0822b0e0ec716 >}}

## Video recording of the talk

And you can also watch the recoding of this presentation here:

{{< youtube L6V6aQixOZU >}}

## Samples demonstrated during the conference

During the presentation, I demonstrated a lot of samples showing ADK in action.
You can find all the [examples](https://github.com/glaforge/ai-agent-protocols/tree/main/adk/src/main/java/agents/adk)
in this [GitHub repository](https://github.com/glaforge/ai-agent-protocols/).
There are also a couple of servers implementing an MCP server and an A2A server agent.

Among those examples, you'll find:

- a simple [science teacher](https://github.com/glaforge/ai-agent-protocols/blob/main/adk/src/main/java/agents/adk/_10_ScienceTeacher.java) agent
- the same [science teacher](https://github.com/glaforge/ai-agent-protocols/blob/main/adk/src/main/java/agents/adk/_12_ScienceTeacher_Live.java) agent but using voice (with a Gemini Live model)
- a [stock ticker](https://github.com/glaforge/ai-agent-protocols/blob/main/adk/src/main/java/agents/adk/_20_StockTicker.java) agent that uses a local Java method to look up (fake) stock prices
- a [news search agent](https://github.com/glaforge/ai-agent-protocols/blob/main/adk/src/main/java/agents/adk/_22_LatestNews_Search.java) configured to use the Google Search built-in tool
- an agent that uses the [built-in Python code executor tool](https://github.com/glaforge/ai-agent-protocols/blob/main/adk/src/main/java/agents/adk/_24_PythonCoder.java)
- an agent taking advantage of [Google Maps grounding](https://github.com/glaforge/ai-agent-protocols/blob/main/adk/src/main/java/agents/adk/_26_LocalGuide_Maps.java) to find local landmarks or restaurants
- a [moon expert](https://github.com/glaforge/ai-agent-protocols/blob/main/adk/src/main/java/agents/adk/_28_MoonExpert_MCP.java)! which calls a remote MCP server
- a [multi-agent](https://github.com/glaforge/ai-agent-protocols/blob/main/adk/src/main/java/agents/adk/_30_SearchAndTweet_SubAgents.java) using the sub-agents approach to search about some topic, and the potentially craft social post messages
- a [trip planner](https://github.com/glaforge/ai-agent-protocols/blob/main/adk/src/main/java/agents/adk/_32_TripPlanner_Sequential.java) agent using a sequential agent
- a [company detective](https://github.com/glaforge/ai-agent-protocols/blob/main/adk/src/main/java/agents/adk/_34_CompanyDetective_Parallel.java) agent using the parallel agent approach to launch different searches in parallel
- a [code refiner](https://github.com/glaforge/ai-agent-protocols/blob/main/adk/src/main/java/agents/adk/_36_CodeRefiner_Loop_Exit.java) agent using the ADK loop agent to loop over different tasks (writing code & critiquing code)
- a [weather forecast](https://github.com/glaforge/ai-agent-protocols/blob/main/adk/src/main/java/agents/adk/_40_WeatherForecast_Callback.java) agent just to show the various callbacks you can configure on an agent
- an agent using a [local agent running in Ollama](https://github.com/glaforge/ai-agent-protocols/blob/main/adk/src/main/java/agents/adk/_50_Coffee_LangChain4j.java), thanks to [my ADK / LangChain4j bridge](https://developers.googleblog.com/en/adk-for-java-opening-up-to-third-party-language-models-via-langchain4j-integration/)
- an example showing how to [load a YAML-defined agent](https://github.com/glaforge/ai-agent-protocols/blob/main/adk/src/main/java/agents/adk/_60_CapitalCity_YAML.java)
- and the bonus for the end: an [agent using the Nano Banana](https://github.com/glaforge/ai-agent-protocols/blob/main/adk/src/main/java/agents/adk/_70_ImageEditor_NanoBanana.java) image generation and edition model

## Updated ADK template project

With the recent (somewhat silent) release of [version 0.3.0](https://github.com/google/adk-java/releases/tag/v0.3.0),
I seized the opportunity to also update my [ADK template project](https://github.com/glaforge/adk-java-maven-template) on GitHub.
In a [recent article](https://glaforge.dev/posts/2025/05/27/adk-java-github-template/), I wrote about this template project,
how you can clone it or reuse it, to get started with ADK for Java easily, with a sample agent, and a Maven build.

## Getting started with a codelab

Additionally to the GitHub [project template](https://github.com/glaforge/adk-java-maven-template),
I have developed a [codelab to build AI agents with ADK for Java](https://goo.gle/codelab-adk-java), for Java developers.
This codelab goes through setting up your environment, writing your first agent, empowering an agent with tools, using the built-in Google Search tool,
mastering the various types of workflow patterns (sub-agent, sequential, parallel, loop).

[![](/img/adk/adk-java-codelab-screenshot.png)](https://goo.gle/codelab-adk-java)