Why initialize HashSet<>(0) to zero?

Question

I love a HashSet<>() and use this eagerly while initializing this with the default constructor:

Set users = new HashSet<>();
         


        

Answer 1

HashSet use HashMap store data:

public HashSet(int initialCapacity) {
map = new HashMap(initialCapacity);
}

while the initialCapacity = 0,

public HashMap(int initialCapacity, float loadFactor) {
    ....
    // Find a power of 2 >= initialCapacity
    int capacity = 1;
    while (capacity < initialCapacity)
        capacity <<= 1;
}

the HashMap capacity is 1.

but if use default constructor:

public HashMap() {
    this.loadFactor = DEFAULT_LOAD_FACTOR;
    threshold = (int)(DEFAULT_INITIAL_CAPACITY * DEFAULT_LOAD_FACTOR);
    table = new Entry[DEFAULT_INITIAL_CAPACITY];
    init();
}

the HashMap capacity is 16*0.75.

So, new HashSet<>(0) save some memroy when init.