equals or identity

[nimo frey]

When I compare two Short values a and b, then I need to compare it via:

a.equals((short) b);

or via

a==b

this:

I have found out, that this a.equals(b); is strangely not the same as this a.equals((short) b);

Should I compare wrapper classes (Integer, Long, Short) via equals or via '==' ? In primitive types, we compare via '=='.

(I know the difference of equals and identity)

[Rob Spoor]

nimo frey wrote:Should I compare wrapper classes (Integer, Long, Short) via equals or via '==' ?

Via equals.

== only works for values between -128 and 127 (inclusive) for Byte, Short, Integer and Long, and for values between 0 and 127 for Character. And only if the object was retrieved using the static valueOf(primitive) method. Otherwise, a new object is created and == will return false.

[Saifuddin Merchant]

nimo frey wrote:
I have found out, that this a.equals(b); is strangely not the same as this a.equals((short) b);

I don't understand why these should return different values. The Short wrapper class has just one overridden equals() method so both of these should give the same result.

Can you provide a code snippet where you end up getting different values for the two?

[nimo frey]

okay thank you!

[nimo frey]

I don't understand why these should return different values. The Short wrapper class has just one overridden equals() method so both of these should give the same result.

I do not understand, either.

Look at this:

Short s = 0;

s.equals(0) // returns false

s==0 // returns true
s.equals((short)0) // returns true

So I have to explicitly cast my 0-value to short. Very cumbersome.

[Joanne Neal]

nimo frey wrote:

I don't understand why these should return different values. The Short wrapper class has just one overridden equals() method so both of these should give the same result.

I do not understand, either.

Look at this:

Short s = 0;

s.equals(0) // returns false

s==0 // returns true
s.equals((short)0) // returns true

So I have to explicitly cast my 0-value to short. Very cumbersome.

That is not what you described in your first post. You said you had two Short values.

Here you have a Short and an int literal (0). The int will be autoboxed into an Integer if you don't cast it, and an Integer will never be equal to a Short.