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Precedence Operator in the Java Programming Language handout for CS 302 by Will Benton (willb@cs) Operator precedence defines the order in which various operators are evaluated. (In fact, you may remember "order of operations" from secondary school algebra.) As an example, let's say we have the following line of Java code: int x = 4 + 3 * 5; The variable x gets the value of evaluating the expression 4 + 3 * 5. There are a couple of ways to evaluate that expression, though: We can either perform the addition first or perform the multiplication first. By choosing which operation to perform first, we are actually choosing between two different expressions: 1. (4 + 3) * 5 == 35 2. 4 + (3 * 5) == 19 In the absence of parentheses, which choice is appropriate? Programming languages answer this question by defining precedence levels for each operator, indicating which is to be performed first. In the case of Java, multiplication takes precedence over addition; therefore, x will get the value 19. For arithmetic expressions, multiplication and division are evaluated before addition and subtraction, just like in mathematics. Of course, just as you might in a math class, you can always parenthesize Java expressions to indicate which are to be evaluated first. Sensible use of parentheses will make your programs easier to read even if your expressions all use the standard evaluation order. This sheet shows the operator precedences for the Java operators you'll be using most frequently in CS 302. On the reverse of this sheet is a chart of the precedence levels for every operator in the Java language, provided in case you're curious! postfix increments and decrements (e.g. x++) evaluated sooner prefix increments and decrements (e.g. ++x) unary positive (+x), unary negative (-x), and logical negation (!x) binary arithmetic operators comparison binary operators binary logical operators assignment operators Comparison operations (e.g. <, >, <=) are evaluated before equality operators (e.g. ==, !=). Multiply (*), divide (/), and modulus (%) operations are evaluated before add (+) and subtract operations (-). evaluated later AND operations (&&) are evaluated before OR (||) operations Copyright 2005-2007 Will C. Benton java-operator-precedence.graf e: Created on Fri Jan 20 2006; modi ed on Wed Feb 21 2007; page 1 of 2 [] . , x++ x-- ~x subscript, member selection, comma (only in for loop headers) postfix increment, postfix decrement, bitwise negation prefix increment, prefix decrement, unary positive, unary negative, logical negation typecasting, object creation multiplication, division, modulus addition, subtraction, string concatenation bitwise shift comparison runtime type compatibility equality and inequality bitwise AND bitwise XOR bitwise OR logical AND logical OR ternary (conditional) ++x --x +x -x !x right-associative (X) new X * / % x+y x-y x+"x" << < >> <= > >>> >= instanceof == & ^ | && || x ? y : z != left-associative += = -= *= /= %= <<= >>= >>>= &= ^= |= assignment and compound assignment right-associative Note: operators with the same precedence level in an expression are evaluated based on their associativity. For example, left-associative operators group from left to right. Therefore, the expression x * y % z is equivalent to (x * y) % z. java-operator-precedence.graf e: Created on Fri Jan 20 2006; modi ed on Wed Feb 21 2007; page 2 of 2 lower precedence This chart (c) 2005-2007 William C. Benton. sources: Chan, Patrick. The Java Developers Almanac 1.4. Addison-Wesley, 2002. Gosling, James, et al. The Java Language Specification, 3e. Addison-Wesley, 2005. higher precedence left-associative

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