Comparing doubles in Java gives odd results

Question

I really can\'get my head around why the following happens:

Double d = 0.0;
System.out.println(d == 0); // is true
System.out.println(d.equals(0)); // is false ?         


        

Answer 1

Number objects only equal to numbers with the same value if they are of the same type. That is:

new Double(0).equals(new Integer(0));
new BigInteger("0").equals(new BigDecimal("0"));

and similar combinations are all false.

In your case, the literal 0 is boxed into an Integer object.