Is it necessary to learn other programming language before learning java ?

Answer 1

No. Basically, you can decide whether you prefer to learn functional programming languages (eg. F#) or Object-Oriented language such as Java or C#. More importantly, it is the fundamental concepts that you need to master first (eg. Object Oriented Programming).

Answer 2

No

Answer 3

is it possible to make simple apps just using java ?

Answer 4

Yes of course. you can see there are abundance of java tutorials out there that provides simple projects.