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Tags

#bloch-effective-java-2ed #java #java-generics

Question

Which is a better version?


public static <E> Set<E> union(Set<? extends E> input1, Set<? extends E> input2)  { /* .. */ }

public static <E> Set<? super E> union(Set<? extends E> input1, Set<? extends E> input2) { /* .. */ }

Answer

The first one is better. Do not use wildcard types as return types. Rather than providing additional flexibility for your users, it would force them to use wildcard types in client code.


public static <E> Set<E> union(Set<? extends E> input1, Set<? extends E> input2)  { /* .. */ }

Tags

#bloch-effective-java-2ed #java #java-generics

Question

Which is a better version?


public static <E> Set<E> union(Set<? extends E> input1, Set<? extends E> input2)  { /* .. */ }

public static <E> Set<? super E> union(Set<? extends E> input1, Set<? extends E> input2) { /* .. */ }

Answer

The first one is better. Do not use wildcard types as return types. Rather than providing additional flexibility for your users, it would force them to use wildcard types in client code.


public static <E> Set<E> union(Set<? extends E> input1, Set<? extends E> input2)  { /* .. */ }

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pdf

owner: piotr.wasik - (no access) - Effective Java (Joshua Bloch), 2ed, p137

Summary

status	not learned	measured difficulty	37% [default]	last interval [days]
repetition number in this series	0	memorised on		scheduled repetition
scheduled repetition interval		last repetition or drill

Details

No repetitions

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