Java: A step further

Start with a remark: Comparison

For comparisons, use "equals"

Immutable

Immutable objects can not be updated after they are created.

More Objects

Heap memory is used by all the parts of the application whereas stack memory is used only by one thread of execution.
Whenever an object is created, it's always stored in the Heap space and stack memory contains the reference to it.

Static sized: Arrays, Dynamic sized: Collections
They are very similar to use but have slight differences.

Operators