I'm not sure what you mean by no promotion taking place because you have a double and a float.
This is from the Java Language Specification 5.6.2.
When an operator applies binary numeric promotion to a pair of operands, each of which must denote a value that is convertible to a numeric type, the following rules apply, in order, using widening conversion (�5.1.2) to convert operands as necessary:
* If any of the operands is of a reference type, unboxing conversion (�5.1.8) is performed. Then: * If either operand is of type double, the other is converted to double. * Otherwise, if either operand is of type float, the other is converted to float. * Otherwise, if either operand is of type long, the other is converted to long. * Otherwise, both operands are converted to type int.
Binary numeric promotion is performed on the operands of certain operators:
* The multiplicative operators *, / and % (�15.17) * The addition and subtraction operators for numeric types + and - (�15.18.2) * The numerical comparison operators <, <=, >, and >= (�15.20.1) * The numerical equality operators == and != (�15.21.1) * The integer bitwise operators &, ^, and | (�15.22.1) * In certain cases, the conditional operator ? : (�15.25)
The reason 5.1 prints out exactly in the last two statements is that there is no conversion taking place.