Java: Summary - Expressions

Parentheses () have three uses: Grouping to control order of evaluation, or for clarity. Eg, (a + b) * (c - d) After a method name to enclose parameters. Eg, x = sum(a, b); Around a type name to form a cast. Eg, i = (int)x; Order of evaluation Higher precedence are done before lower precedence. Left to right among equal precedence except: unary, assignment, conditional operators. Abbreviations i, j - integer (int, long, short, byte, char) values. m, n - numeric values (integers, double, or float). b, c - boolean; x, y - any primitive or object type. s, t - String; a - array; o - object; co - class or object

Operator Precedence . [] (args) post ++ -- ! ~ unary + - pre ++ -- (type) new * / % + - << >> >>> < <= > >= instanceof == != & ^ | && || ?: = += -= etc Remember only unary operators * / % + - comparisons && || = assignments Use () for all others

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Arithmetic Operators The result of arithmetic operators is double if either operand is double, else float if either operand is float, else long if either operand is long, else int. ++i Add 1 to i before using the value in the current expression --i As above for subtraction i++ Add 1 to i after using the value in the current expression i-- As above for subtraction n + m Addition. Eg 7+5 is 12, 3 + 0.14 is 3.14 n - m Subtraction n * m Multiplication. Eg 3 * 6 is 18 n / m Division. Eg 3.0 / 2 is 1.5 , 3 / 2 is 1 n % m Remainder (Mod) after division of n by m. Eg 7 % 3 is 1 Comparing Primitive Values The result of all comparisons is boolean (true or false). == != < <= > >= Logical Operators The operands must be boolean. The result is boolean. b && c Conditional "and". true if both operands are true, otherwise false. Short circuit evaluation. Eg (false && anything) is false. b || c Conditional "or". true if either operand is true, otherwise false. Short circuit evaluation. Eg (true || anything) is true. !b true if b is false, false if b is true. b & c "And" which always evaluate both operands (not short circuit). b | c "Or" which always evaluate both operands (not short circuit). b ^ c "Xor" Same as b != c Conditional Operator b?x:y if b is true, the value is x, else y. x and y must be the same type.

Assignment Operators = Left-hand-side must be an lvalue. += -= *= ... All binary operators (except && and ||) can be combined with assignment. Eg a += 1 is the same as a = a + 1 Bitwise Operators Bitwise operators operate on bits of ints. Result is int. i & j Bits are "anded" - 1 if both bits are 1. 5 & 3 is 1. i | j Bits are "ored" - 1 if either bit is 1. 5 | 3 is 7. i ^ j Bits are "xored" - 1 if bits are different. 5 ^ 3 is 6. ~i Bits are complemented (0 -> 1, 1 -> 0) i <<> Bits in i are shifted j bits to the left, zeros inserted on right. 5 <<> i >> j Bits in i are shifted j bits to the right. Sign bits inserted on left. 5 >> 2 is 1. i >>> j Bits in i are shifted j bits to the right. Zeros inserted on left. Casts Use casts when "narrowing" the range of a value. From narrowest to widest the primitive types are: byte, short, char, int, long, float, double. Objects can be assigned without casting up the inheritance hierarchy. Casting is required to move down the inheritance hierarchy (downcasting). (t)x Casts x to type t Object Operators co.f Member. The f field or method of object or class co. x instanceof co true if the object x is an instance of class co, or is an instance of the class of co. a[i] Array element access. s + t String concatentation if one or both operands are Strings. x == y true if x and y refer to the same object, otherwise false (even if values of the objects are the same). x != y As above for inequality. comparison Compare object values with .equals() or .compareTo() x = y Assignment copies the reference, not the object.