The Java® Language Specification, Java SE 7 Edition, Fourth Edition

15.26. Assignment Operators

There are 12 assignment operators; all are syntactically right-associative (they group right-to-left). Thus, a=b=c means a=(b=c), which assigns the value of c to b and then assigns the value of b to a.

AssignmentExpression:    ConditionalExpression    AssignmentAssignment:    LeftHandSide AssignmentOperator AssignmentExpressionLeftHandSide:    ExpressionName    FieldAccess    ArrayAccessAssignmentOperator: one of    = *= /= %= += -= <<= >>= >>>= &= ^= |=

The result of the first operand of an assignment operator must be a variable, or a compile-time error occurs.

This operand may be a named variable, such as a local variable or a field of the current object or class, or it may be a computed variable, as can result from ...