转自原文:http://www.yiibai.com/java/java_basic_operators.html
Java提供了一组运算符丰富的操纵变量。我们可以把所有的Java操作符为以下几组:
- 算术运算符
- 关系运算符
- 位运算符
- 逻辑运算符
- 赋值运算符
- 其它运算符
算术运算符:
算术运算符用于在数学表达式中,他们是在代数中使用的方法相同。下表列出了算术运算符:
假设整型变量A=10和变量B=20,则:
运算符 | 描述 | 实例 |
---|---|---|
+ | Addition - Adds values on either side of the operator | A + B = 30 |
- | Subtraction - Subtracts right hand operand from left hand operand | A - B = -10 |
* | Multiplication - Multiplies values on either side of the operator | A * B = 200 |
/ | Division - Divides left hand operand by right hand operand | B / A = 2 |
% | Modulus - Divides left hand operand by right hand operand and returns remainder | B % A = 0 |
++ | Increment - Increases the value of operand by 1 | B++ =21 |
-- | Decrement - Decreases the value of operand by 1 | B-- =19 |
关系运算符:
有下列由Java语言支持的关系运算符
假设变量A=10和变量B=20,则:
运算符 | 描述 | 实例 |
---|---|---|
== | Checks if the values of two operands are equal or not, if yes then condition becomes true. | (A == B) is not true. |
!= | Checks if the values of two operands are equal or not, if values are not equal then condition becomes true. | (A != B) is true. |
> | Checks if the value of left operand is greater than the value of right operand, if yes then condition becomes true. | (A > B) is not true. |
< | Checks if the value of left operand is less than the value of right operand, if yes then condition becomes true. | (A < B) is true. |
>= | Checks if the value of left operand is greater than or equal to the value of right operand, if yes then condition becomes true. | (A >= B) is not true. |
<= | Checks if the value of left operand is less than or equal to the value of right operand, if yes then condition becomes true. | (A <= B) is true. |
按位运算符:
Java定义了几个位运算符,它可以应用到整数类型,长型,整型,短整型,字符和字节。
位运算符作用于位,并执行逐位操作。假设当a =60和b= 13; 现在以二进制格式,他们将会如下:
a = 0011 1100
b = 0000 1101
-----------------
a&b = 0000 1100
a|b = 0011 1101
a^b = 0011 0001
~a = 1100 0011
下表列出了按位运算符:
假设整型变量A=60和变量B=13,则:
运算符 | 描述 | 实例 |
---|---|---|
& | Binary AND Operator copies a bit to the result if it exists in both operands. | (A & B) will give 12 which is 0000 1100 |
| | Binary OR Operator copies a bit if it exists in either operand. | (A | B) will give 61 which is 0011 1101 |
^ | Binary XOR Operator copies the bit if it is set in one operand but not both. | (A ^ B) will give 49 which is 0011 0001 |
~ | Binary Ones Complement Operator is unary and has the effect of ‘flipping‘ bits. | (~A ) will give -61 which is 1100 0011 in 2‘s complement form due to a signed binary number. |
<< | Binary Left Shift Operator. The left operands value is moved left by the number of bits specified by the right operand. | A << 2 will give 240 which is 1111 0000 |
>> | Binary Right Shift Operator. The left operands value is moved right by the number of bits specified by the right operand. | A >> 2 will give 15 which is 1111 |
>>> | Shift right zero fill operator. The left operands value is moved right by the number of bits specified by the right operand and shifted values are filled up with zeros. | A >>>2 will give 15 which is 0000 1111 |
逻辑运算符:
下表列出了逻辑运算符:
假设布尔变量A=ture,变量B=false,那么:
运算符 | 描述 | 实例 |
---|---|---|
&& | Called Logical AND operator. If both the operands are non-zero, then the condition becomes true. | (A && B) is false. |
|| | Called Logical OR Operator. If any of the two operands are non-zero, then the condition becomes true. | (A || B) is true. |
! | Called Logical NOT Operator. Use to reverses the logical state of its operand. If a condition is true then Logical NOT operator will make false. | !(A && B) is true. |
赋值运算符:
有下列由Java语言支持赋值操作符:
运算符 | 描述 | 实例 |
---|---|---|
= | Simple assignment operator, Assigns values from right side operands to left side operand | C = A + B will assign value of A + B into C |
+= | Add AND assignment operator, It adds right operand to the left operand and assign the result to left operand | C += A is equivalent to C = C + A |
-= | Subtract AND assignment operator, It subtracts right operand from the left operand and assign the result to left operand | C -= A is equivalent to C = C - A |
*= | Multiply AND assignment operator, It multiplies right operand with the left operand and assign the result to left operand | C *= A is equivalent to C = C * A |
/= | Divide AND assignment operator, It divides left operand with the right operand and assign the result to left operand | C /= A is equivalent to C = C / A |
%= | Modulus AND assignment operator, It takes modulus using two operands and assign the result to left operand | C %= A is equivalent to C = C % A |
<<= | Left shift AND assignment operator | C <<= 2 is same as C = C << 2 |
>>= | Right shift AND assignment operator | C >>= 2 is same as C = C >> 2 |
&= | Bitwise AND assignment operator | C &= 2 is same as C = C & 2 |
^= | bitwise exclusive OR and assignment operator | C ^= 2 is same as C = C ^ 2 |
|= | bitwise inclusive OR and assignment operator | C |= 2 is same as C = C | 2 |
其它运算符
Java 语言支持一些其他的运算符。
条件运算符 ( ? : ):
条件运算符也被称为三元运算符。该运算符包括三个操作数,用于评估计算布尔表达式。此运算符的目标是确定哪些值应分配给该变量。可写为:
variable x = (expression) ? value if true : value if false
下面是例子:
public class Test { public static void main(String args[]){ int a , b; a = 10; b = (a == 1) ? 20: 30; System.out.println( "Value of b is : " + b ); b = (a == 10) ? 20: 30; System.out.println( "Value of b is : " + b ); } }
这将产生以下结果:
Value of b is : 30 Value of b is : 20
instanceof运算符:
这个操作符只用于对象引用变量。操作检查对象是否为特定类型(类类型或接口类型)。instanceof 运算符被写为:
( Object reference variable ) instanceof (class/interface type)
如果运算符的左侧提到的变量的对象传递了IS-A检查右侧的类/接口类型,那么结果将为 true。下面是例子:
public class Test { public static void main(String args[]){ String name = "James"; // following will return true since name is type of String boolean result = name instanceof String; System.out.println( result ); } }
这将产生以下结果:
true
这个操作符仍然会返回true,如果被比较的对象是分配在右侧的类型兼容。下面是一个例子:
class Vehicle {} public class Car extends Vehicle { public static void main(String args[]){ Vehicle a = new Car(); boolean result = a instanceof Car; System.out.println( result ); } }
这将产生以下结果:
true
优先级的Java操作符:
运算符优先级决定的条件在表达式中分组。这会影响一个表达式如何计算。某些运算符的优先级高于其它,例如,乘法运算符的优先级比加法运算高:
例如x= 7+3* 2;这里x被赋值13,而不是20,因为运算符*的优先级高于+,所以它首先被乘以3 * 2,然后加7。
这里,具有最高优先级的操作出现在表格上方,那些具有最低出现在底部。在表达式中,优先级较高的运算符将首先评估计算。
分类 | 运算符 | 关联 |
---|---|---|
Postfix | () [] . (dot operator) | Left to right |
Unary | ++ - - ! ~ | Right to left |
Multiplicative | * / % | Left to right |
Additive | + - | Left to right |
Shift | >> >>> << | Left to right |
Relational | > >= < <= | Left to right |
Equality | == != | Left to right |
Bitwise AND | & | Left to right |
Bitwise XOR | ^ | Left to right |
Bitwise OR | | | Left to right |
Logical AND | && | Left to right |
Logical OR | || | Left to right |
Conditional | ?: | Right to left |
Assignment | = += -= *= /= %= >>= <<= &= ^= |= | Right to left |
Comma | , | Left to right |