learning XI

I am new to SAP, Taken training on ABAP and Java.

I am interested to learn XI. My question is How a good ABAPer and good JAVA resource can easily learn XI compared to others who don't know ABAP and JAVA ?

otherwise

how abap and java are useful in XI ? do we need to code in abap or java in XI ?

Please clarify me.

Thanks,

Kiran