CPLEX & Java 7. Solving problems with a quadratic objective

Solution to a very simple quadratic model: a quadratic objective with linear constraints.

[mohdshahrukh]

how to declare a variable which is multiple of another variable like if x and y are variables then
and y=2x then how to declare y

[la]

Hello 
I'm wondering which is much better and powerful to solve optimization, IBM CPLEX or JAVA ??