The Java Language Specification, Third Edition

15.18 Additive Operators EXPRESSIONS
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• If the dividend is finite and the divisor is an infinity, the result equals the dividend.
• If the dividend is a zero and the divisor is finite, the result equals the dividend.
• In the remaining cases, where neither an infinity, nor a zero, nor NaN is
involved, the floating-point remainder r from the division of a dividend n by a
divisor d is defined by the mathematical relation r = n– ( d ⋅ q)
where q is an
integer that is negative only if n ⁄ d is negative and positive only if n ⁄
d is
positive, and whose magnitude is as large as possible without exceeding the
magnitude of the true mathematical quotient of n and d.
Evaluation of a floating-point remainder operator % never throws a run-time
exception, even if the right-hand operand is zero. Overflow, underflow, or loss of
precision cannot occur.
Examples:
5.0%3.0 produces 2.0
5.0%(-3.0) produces 2.0
(-5.0)%3.0 produces -2.0
(-5.0)%(-3.0) produces -2.0
15.18 Additive Operators
The operators + and - are called the additive operators. They have the same precedence
and are syntactically left-associative (they group left-to-right).
AdditiveExpression:
MultiplicativeExpression
AdditiveExpression + MultiplicativeExpression
AdditiveExpression - MultiplicativeExpression
If the type of either operand of a + operator is String, then the operation is
string concatenation.
Otherwise, the type of each of the operands of the + operator must be a type
that is convertible (§5.1.8) to a primitive numeric type, or a compile-time error
occurs.
In every case, the type of each of the operands of the binary - operator must
be a type that is convertible (§5.1.8) to a primitive numeric type, or a compiletime
error occurs.
DRAFT