The Java Language Specification, Third Edition

EXPRESSIONS Constant Expression 15.28
operand then assigns 4 to k, calculates the value 6 for k+2, and then multiplies
4 by 6 to get 24. This is added to the saved value 1 to get 25, which is then stored
into k by the += operator. An identical analysis applies to the case that uses a[0].
In short, the statements
k += (k = 4) * (k + 2);
a[0] += (a[0] = 4) * (a[0] + 2);
behave in exactly the same manner as the statements:
k = k + (k = 4) * (k + 2);
a[0] = a[0] + (a[0] = 4) * (a[0] + 2);
15.27 Expression
An Expression is any assignment expression:
Expression:
AssignmentExpression
Unlike C and C++, the Java programming language has no comma operator.
15.28 Constant Expression
. . . the old and intent expression was a constant, not an occasional, thing . . .
A Tale of Two Cities
ConstantExpression:
Expression
A compile-time constant expression is an expression denoting a value of
primitive type or a String that does not complete abruptly and is composed
using only the following:
• Literals of primitive type and literals of type String (§3.10.5)
• Casts to primitive types and casts to type String
DRAFT
• The unary operators +, -, ~, and ! (but not ++ or --)
• The multiplicative operators *, /, and %
• The additive operators + and -
• The shift operators , and >>>
• The relational operators = (but not instanceof)
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