Operators Associativity

运算符优先级表

优先级	运算符	结合性
1	() [] .	从左到右
2	! +(正)  -(负) ~ ++ --	从右向左
3	* / %	从左向右
4	+(加) -(减)	从左向右
5	<< >> >>>	从左向右
6	< <= > >= instanceof	从左向右
7	==   !=	从左向右
8	&(按位与)	从左向右
9	^	从左向右
10	|	从左向右
11	&&	从左向右
12	||	从左向右
13	?:	从右向左
14	= += -= *= /= %= &= |= ^=  ~=  <<= >>=   >>>=	从右向左

 

说明：

 

　　1、 该表中优先级按照从高到低的顺序书写，也就是优先级为1的优先级最高，优先级14的优先级最低。

　　2、 结合性是指运算符结合的顺序，通常都是从左到右。从右向左的运算符最典型的就是负号，例如3+-4，则意义为3加-4，符号首先和运算符右侧的内容结合。

　　3、 instanceof作用是判断对象是否为某个类或接口类型，后续有详细介绍。

　　4、 注意区分正负号和加减号，以及按位与和逻辑与的区别

　　其实在实际的开发中，不需要去记忆运算符的优先级别，也不要刻意的使用运算符的优先级别，对于不清楚优先级的地方使用小括号去进行替代，示例代码：

         int m = 12;

         int n = m << 1 + 2;

         int n = m << (1 + 2); //这样更直观

 

　　　int r = (2 * l - m + 3 * n) >>1- 128;//首先执行的是1-128，然后在进行>>运算！！，所以要加括号

　　　int r = ((2 * l - m + 3 * n) >>1)- 128

 

C++运算符优先级

　　

Operator	Description	Example	Overloadable
Group 1 (no associativity)
::	Scope resolution operator	Class::age = 2;	NO
Group 2
()	Function call	isdigit('1')	YES
()	Member initalization	c_tor(int x, int y) : _x(x), _y(y*10){};	YES
[]	Array access	array[4] = 2;	YES
->	Member access from a pointer	ptr->age = 34;	YES
.	Member access from an object	obj.age = 34;	NO
++	Post-increment	for( int i = 0; i < 10; i++ ) cout << i;	YES
--	Post-decrement	for( int i = 10; i > 0; i-- ) cout << i;	YES
const_cast	Special cast	const_cast<type_to>(type_from);	NO
dynamic_cast	Special cast	dynamic_cast<type_to>(type_from);	NO
static_cast	Special cast	static_cast<type_to>(type_from);	NO
reinterpret_cast	Special cast	reinterpret_cast<type_to>(type_from);	NO
typeid	Runtime type information	cout &laquo; typeid(var).name();  cout &laquo; typeid(type).name();	NO
Group 3 (right-to-left associativity)
!	Logical negation	if( !done ) …	YES
not	Alternate spelling for !
~	Bitwise complement	flags = ~flags;	YES
compl	Alternate spelling for ~
++	Pre-increment	for( i = 0; i < 10; ++i ) cout << i;	YES
--	Pre-decrement	for( i = 10; i > 0; --i ) cout << i;	YES
-	Unary minus	int i = -1;	YES
+	Unary plus	int i = +1;	YES
*	Dereference	int data = *intPtr;	YES
&	Address of	int *intPtr = &data;	YES
new	Dynamic memory allocation	long *pVar = new long;  MyClass *ptr = new MyClass(args);	YES
new []	Dynamic memory allocation of array	long *array = new long[n];	YES
delete	Deallocating the memory	delete pVar;	YES
delete []	Deallocating the memory of array	delete [] array;	YES
(type)	Cast to a given type	int i = (int) floatNum;	YES
sizeof	Return size of an object or type	int size = sizeof floatNum;  int size = sizeof(float);	NO
Group 4
->*	Member pointer selector	ptr->*var = 24;	YES
.*	Member object selector	obj.*var = 24;	NO
Group 5
*	Multiplication	int i = 2 * 4;	YES
/	Division	float f = 10.0 / 3.0;	YES
%	Modulus	int rem = 4 % 3;	YES
Group 6
+	Addition	int i = 2 + 3;	YES
-	Subtraction	int i = 5 - 1;	YES
Group 7
<<	Bitwise shift left	int flags = 33 << 1;	YES
>>	Bitwise shift right	int flags = 33 >> 1;	YES
Group 8
<	Comparison less-than	if( i < 42 ) …	YES
<=	Comparison less-than-or-equal-to	if( i <= 42 ) ...	YES
>	Comparison greater-than	if( i > 42 ) …	YES
>=	Comparison greater-than-or-equal-to	if( i >= 42 ) ...	YES
Group 9
==	Comparison equal-to	if( i == 42 ) ...	YES
eq	Alternate spelling for ==
!=	Comparison not-equal-to	if( i != 42 ) …	YES
not_eq	Alternate spelling for !=
Group 10
&	Bitwise AND	flags = flags & 42;	YES
bitand	Alternate spelling for &
Group 11
^	Bitwise exclusive OR (XOR)	flags = flags ^ 42;	YES
xor	Alternate spelling for ^
Group 12
|	Bitwise inclusive (normal) OR	flags = flags | 42;	YES
bitor	Alternate spelling for |
Group 13
&&	Logical AND	if( conditionA && conditionB ) …	YES
and	Alternate spelling for &&
Group 14
||	Logical OR	if( conditionA || conditionB ) ...	YES
or	Alternate spelling for ||
Group 15 (right-to-left associativity)
? :	Ternary conditional (if-then-else)	int i = (a > b) ? a : b;	NO
Group 16 (right-to-left associativity)
=	Assignment operator	int a = b;	YES
+=	Increment and assign	a += 3;	YES
-=	Decrement and assign	b -= 4;	YES
*=	Multiply and assign	a *= 5;	YES
/=	Divide and assign	a /= 2;	YES
%=	Modulo and assign	a %= 3;	YES
&=	Bitwise AND and assign	flags &= new_flags;	YES
and_eq	Alternate spelling for &=
^=	Bitwise exclusive or (XOR) and assign	flags ^= new_flags;	YES
xor_eq	Alternate spelling for ^=
|=	Bitwise normal OR and assign	flags |= new_flags;	YES
or_eq	Alternate spelling for |=
<<=	Bitwise shift left and assign	flags <<= 2;	YES
>>=	Bitwise shift right and assign	flags >>= 2;	YES
Group 17
throw	throw exception	throw EClass(“Message”);	NO
Group 18
,	Sequential evaluation operator	for( i = 0, j = 0; i < 10; i++, j++ ) …	YES

C#中的优先级

 

优先级	类别	运算符
1	基本	（x） x.y f(x) a[x] x++ x――new typeof sizeof checked unchecked
2	单目	+ － ！ ～ ++x ――x (T)x
3	乘法与除法	* / %
4	加法与减法	+ －
5	移位运算	<< >>
6	关系运算	﹤ > <= >= is
7	条件等	= = ! =
8	位逻辑与	&
9	位逻辑异或	^
10	位逻辑或	|
11	条件与	&&
12	条件或	‖
13	条件	?:
14	赋值	= *= /= %= += －= <<= >>= &= ^= |=