java - what happens if hashCode is not overriden? [duplicate]

Answer 1

**type of field**             **hash code formula**

boolean                       fieldHash = f ? 0 : 1

any integer type except long  fieldHash = (int) f

long                          fieldHash = (int) (f ^ (f >>> 32))

float                         fieldHash = Float.floatToIntBits( f )

double                        int v=Double.doubleToLongBits(f)

fieldHash                     (int) (v ^ (v >>> 32))

any Object reference          fieldHash = f.hashCode()

If you write a custom type you are responsible for creating a good hashCode implementation that will best represent the state of the current instance.

http://content.hccfl.edu/pollock/AJava/HashCode.htm