Ethereum Cookbook

Web3J

1. Web3J is a Java and Android library for interacting with nodes and smart contracts on the Ethereum network.

2. Add the following dependencies to Maven to start using Web3J:

// Java 8<dependency>
  <groupId>org.web3j</groupId>
  <artifactId>core</artifactId>
  <version>3.3.1</version>
</dependency>// Android<dependency>
  <groupId>org.web3j</groupId>
  <artifactId>core</artifactId>
  <version>3.3.1-android</version>
</dependency>

3. If you are using Gradle, then use the following methods:

// Java 8compile ('org.web3j:core:3.3.1')// Androidcompile ('org.web3j:core:3.3.1-android')

4. To connect to a node and initialize an object, use Web3J.build. It defaults to localhost:8545 and can be changed:

Web3j web3 = Web3j.build(new HttpService()); 

5. To send ...