Modern programming languages require generics

Re:Modern programming languages require generics by kaba0 on Tuesday May 24, 2022 @01:11PM (#31494811)

That is also not true — Java’s generics don’t add any overhead. If you would have written an ArrayList implementation before generics you would have had the exact same compiled method signature like put(Object o) and Object get() - the only difference is that it would not have been type safe, that is you could have inserted a String into it while you might have expected to get an Integer on the other side.

So generics are completely a language semantic concept in case of Java, with no performance detriment/benefit. Of course more information can be used up for better optimizations as well, see Rust’s or C++’s generics/templates.

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Re:Modern programming languages require generics by titzer on Tuesday May 24, 2022 @04:16PM (#31497062)

The javac source compiler erases source-level types and inserts casts into the bytecode (at usage sites, not within the generic class). So if you have ArrayList<T>, it will generate one version of ArrayList. But usage sites will have casts inserted where necessary. In particular, in a use of put() on the outside doesn't need a cast (because the single implementation of ArrayList uses Object underneath), but get() will have a cast from Object to String at the call site.

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