JUNIT- what is the best way to share data between different test class

I am writing JUNIT for big application and the object are too big to initialize inside the code it self. so we decided to put the object inside json files . Now its more readable and the code is clean . But as I I was wiring my code I understand that the same json file could be share among other test classes. I dont want to parse is again and again in each test. I thought about single-tone but maybe there is a nicer way to do it via rules or by inheritance.

Thanks moshes