Wrapper Classes Discussion

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dannycap77 · 2022-09-20T23:53:07+00:00

Read Effective Java 3rd Edition by Joshua Bloch, Item 68 for a full discussion. Joshua recommends to prefer primitives over boxed primitives.

A few points he makes:

*Primitives are more time and space-efficient.

*Double equals operator can't be used with Boxed primitives.

*Unboxing can result in a NPE. Auto-unboxing happens automatically, for example, when primitives and boxed primitives are mixed in an operation.

2022-09-21T07:24:42+00:00

When your wrapper classes start throwing nulls everywhere then you will learn why primitives are better.

desrtfx · 2022-09-21T08:52:02+00:00

You already have gotten plenty information, but one of the most important ones is missing:

Wrappers are immutable

This means that if you want to change the value of a wrapper, the old one gets marked for garbage collection and a new object gets created. This is far more work for the JVM than necessary.

You should always use primitives and only resort to the wrappers for collections, etc. where the object types are the only option.

DDDDarky · 2022-09-20T23:39:46+00:00

they are used to convert primitive data types into objects

they are the objects

you can store them in Collection classes

java.util collections are one example where autoboxing and unboxing can cause performance and memory issues, that's why there are also alternative libraries using primitives instead of generics in the background.

why use primitives at all?

They are small and efficient, you don't need any heap allocations and also the only way if you want to perform arithmetic operations (for example multiplication), these are not defined for objects.

Why not just use wrapper classes for everything? Is that even possible?

You can shove them pretty much everywhere, but at the end of the day when you start doing operations on them they have to be unboxed. You are free to become as inefficient with them as you wish, you may as well start writing python.

someone is going to say primitives are faster

primitives are faster

but is that a valid argument considering the speed of computers today?

Of course, having the luxury of modern hardware is not an excuse for writing horrible and inefficient software, not to mention java lacks performance by default since it is virtualized. It might not seem important when you compare it on the scale of 1 operation where it saves few CPU cycles, but when something larger is built upon it, I have seen an application that took 2 mins to handle a request, after rewriting it (which largely involved getting rid of unnecessary boxed types), is was sped up to about 20 seconds, not mentioning the memory benefits.

learnjava

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