HelloWorld project doesn't compile

I was trying to follow the tutorial https://learn.aion.network/docs/aion-deploy-java-smart-contract-maven
I am getting the following error

~/aion/hello-world/src/main/java/com/helloworld/HelloAvm.java:[3,24] cannot find symbol
  symbol:   class ABIDecoder
  location: package org.aion.avm.api

The aion.avm.api doesn’t have a decoder class. I checked on github and couldn’t find it either.
How do I resolve this?

What was the command you were running?

Followed the instructions in the link. Got the error at
mvn clean install

What happened when you ran mvn initialize?

Got the following output
[INFO] Scanning for projects…
[WARNING] Some problems were encountered while building the effective model for com.helloworld:hello-world:jar:1.0
[WARNING] ‘build.plugins.plugin.version’ for org.apache.maven.plugins:maven-jar-plugin is missing. @ line 40, column 21
[WARNING] ‘dependencies.dependency.systemPath’ for org.aion:avm-lib:jar refers to a non-existing file ~/aion/hello-world/lib/avm.jar @ line 28, column 25
[WARNING] It is highly recommended to fix these problems because they threaten the stability of your build.
[WARNING] For this reason, future Maven versions might no longer support building such malformed projects.
[INFO] ---------------------< com.helloworld:hello-world >---------------------
[INFO] Building hello-world 1.0
[INFO] --------------------------------[ jar ]---------------------------------
[INFO] — aion4j-maven-plugin:0.5.0:init (default) @ hello-world —
[INFO] avm.jar doesn’t exist. Copying the default avm.jar to ~/aion/hello-world/lib folder.
[INFO] org-aion-avm-api.jar doesn’t exist. Copying the default org-aion-avm-api.jar to ~/aion/hello-world/lib folder.
[INFO] org-aion-avm-userlib.jar doesn’t exist. Copying the default org-aion-avm-userlib.jar to ~/aion/hello-world/lib folder.
[INFO] version doesn’t exist. Copying the default version to ~/aion/hello-world/lib folder.
[INFO] ------------------------------------------------------------------------
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 0.430 s
[INFO] Finished at: 2019-03-29T10:47:33+05:30
[INFO] ------------------------------------------------------------------------