Can I call hashCode() into equals()

Question

Hi,
I implemented a class MyObject that overrides the method hashCode() that respect the general contract and the resulting hashcode value is stored in a data member of my class MyObject.
I also overrided the equals() that looks like this:
public boolean equals(Object obj) {
if (obj == null) return false;
if (obj == this) return true;
if (other instanceof MyObject == false) {
return false;
.... complex tests to check the equality that take a long time....
To optimize the equals() I would like to do:
public boolean equals(Object obj) {
if (obj == null) return false;
if (obj == this) return true;
if (other instanceof MyObject == false) {
return false;
// use the hashCode, if different, no need to make the complex checks
if (hasCodeValue_ != obj.hashCode()) {
return false;
.... complex tests to check the equality
I think it should work because the hashCode is different when the objects are different, but I can't find any example of equals() implementation that uses the hascode(), is there any reason for that ? Thanks for your help, BR,
Sebastien.

Answer 1

Would you clarify for me please?
Do you mean that the hashCode method will naturally be
faster because something like String.hashCode() will
return faster than String.equals(otherString) ?Equals methods usually require a few checks before they really start comparing things. They check to see if the objects are the same, they check to see of the object passed in was null, they check the type of the argument and then they cast it. Then they start comparing members and if any of their members are Objects there's more of that.
Hashcode methods just go right at the values. And like you said, they can be cached in a lot of cases like String.
Or do you mean that one should take care to write
hashCode methods that are very fast?
If the latter, I'd like to hear about how you make
sure of that.Well, you could eliminate fields from the calculation but that might produce bad results. Generally, you just don't do a lot of complicated operations.