Calls from recruiters and even interviews are not the same as job offers.
You need to be applying for jobs yourself too; work on customising your resume to each employer and think about how to show that you really do meet their needs and differentiate yourself from all the other recent graduates who want work as Java programmers.
Do you contribute to open source projects? Do you have any projects on your resume that might interest someone? Getting involved in things like this also increase your 'networking opportunities' too. It's just possible that you could end up speaking to someone on a project like this whose full time employer is looking for someone with your skills.
Your question gives the impression that you think that getting a job is a numbers game, that if you get enough phone calls from recruiters then you'll get x% of them turn into interviews and then y% of those will turn into job offers. That isn't the case at all.
There's no magic "get lots of job interviews with this one weird trick" hack that everyone except you knows about. It's perfectly possible to have 100 interviews as a poorly prepared candidate and never get a job and equally possible to prepare well and land a good job with your first interview. Finding a job is less about getting lots of chances and more about making the most of the chances you get.