All the Operators Precedence An operator with higher precedence is done earlier prededes one with lower precedence A higher precedence is indicated with a lower number zero is the highest precedence Most of the time operators with equal precedence are done left to right Examples 3 4 5 gives 23 10 5 2 gives 3 Exceptions unary operators casts assignment operators the ternary operator all done right to left Postfix operators parameters Parameter lists Brackets indicate indexing into an array Accesses methods and variables expr expr Postincrement postdecrement Unary prefix operators expr Preincrement expr Predecrement Unary plus and unary minus Logical negation not Bitwise complement invert every bit Object creation and casting new Create a new instance of a class type Cast convert to the given type Slides are in order of decreasing precedence Higher precedence means more tightly bound The lowest precedence operator is the main operator in an expression Multiplicative operators Multiply Divide Modulus These all have the same precedence Additive operators Add Subtract Shift operators Left shift end off For small integers this is equivalent to multiplying by a power of two Example 100 3 gives 800 Right shift with sign extension For small integers this is equivalent to an integer divide by a power of two Example 100 2 gives 25 Right shift with zero fill Does not make sense for numbers Relational operators Less than Less than or equal to Greater than Greater than or equal to These all have the same precedence and it is higher than equality inequality tests Equality and inequality Test if equal For primitive types tests if the values are equal For objects tests if both sides refer to the same object Test if not equal For primitive types tests if the values are unequal For objects tests if the sides refer to different objects AND AND For integral types ANDs each corresponding pair of bits For booleans performs the logical AND operation Boolean is like but both operands are evaluated even if it is possible to decide the result from the left operand alone Exclusive OR XOR For integral types XORs each corresponding pair of bits For booleans performs the logical XOR operation a b is true if either a is true or b is true but not both There is no operation OR OR For integral types ORs each corresponding pair of bits For booleans performs the logical OR operation Boolean is like but both operands are evaluated even if it is possible to decide the result from the left operand alone The ternary operator boolean expr expression 1 expression 2 This is like if then else for values rather than for statements If the boolean expr evaluates to true the result is expression 1 else it s expression 2 Example max a b a b sets the variable max to the larger of a and b expression 1 and expression 2 need not be the same type but either result must be useable The ternary operator is right associative Use parentheses if more than one ternary operator The assignment operators I The assignment operators have the lowest precedence Assignment is an operation Assignment is right associative a b c 7 5 w assigns 7 5 w to c then assigns c to b then assigns b to a if all these assignments are legal Example if line reader newLine null The assignment operators II There are a lot of assignment operations besides variable expression means the same as variable variable expression variable expression means the same as variable variable expression variable expression means the same as variable variable expression variable expression means the same as variable variable expression The assignment operators III variable expression means the same as variable variable expression variable expression means the same as variable variable expression variable expression means the same as variable variable expression variable expression means the same as variable variable expression The assignment operators IV variable expression means the same as variable variable expression variable expression means the same as variable variable expression variable expression means the same as variable variable expression What you need to know You should understand what each operator does Parameter lists array indexing and the dot operator are done first In arithmetic the unary operators and are done first then multiplication and division then addition and subtraction All assignment operators are done last For anything else it s a good idea to use parentheses anyway even if you remember the order of precedence other people won t The End
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