What is the use of Collections.EMPTY_MAP, EMPTY_LIST, EMPTY_SET

Question

Since they are all the same, why do they need it?

Answer 1

This is sometimes the best alternative to returning null.

public List<?> getList(){
    if(list == null){
        return Collections.emptyList();
    }

    return list;
}

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Answer 2

These are convenient functions: for functions that must return a nonzero value, you can use them, and you do not need to create a new object, and you can perform equality checks on them.

Answer 3

:

** // , EMPTY_something List/Map. Collections.java, EmptyList, EmptyMap , ArrayList. HashMap.

** Save JVM heaps in space since there is no initial capacity for these empty collections.

The above may not seem very important, however, an important consideration and best practices.

Answer 4

Return an immutable list in order; also its even the preferred way, unless the documentation indicates otherwise.