In the below code

Question

@Override
public int hashCode() {
final int prime = 31;
int result = 1;
result = prime * result + ((name == null) ? 0 : name.hashCode());
return result;
}
I dont understand why prime = 31. And why would happen if i keep another number.
And why is result= 1.

Answer 1

A very good article for the reson why prime is 31, is the following :
https://www.javamex.com/tutorials/collections/hash_function_technical_2.shtml
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By multiplying, bits are shifted to the left. This uses more of the available space of hash codes, reducing collisions.

By not using a power of two, the lower-order, rightmost bits are populated as well, to be mixed with the next piece of data going into the hash.

The expression n * 31 is equivalent to (n << 5) - n.