singleton class eager vs lazy hibernate eager vs lazy hibernate types of caching 1st level - session 2nd levvel - session factory DCL commands DDL commands primary vs unique key idempotent methods types bean wiring in spring types of injection in spring default bean scope Program : reverse a string Program : how to write in lambda function program : to read a file and print tis content stop singleton from breaking in reflection @Qualifier marker interface throw vs throws linkedhashmap vs treemap spring autowiring types SQL - 3rd highest age from table emp (name, age) why concurrentmodificationexception ? how to resolve?