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 « typeid(var).name(); cout « 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 | = *= /= %= += －= <<= >>= &= ^= |= |
