新手了解java基础知识(二)

算数运算符

算术运算符用在数学表达式中，它们的作用和在数学中的作用一样。下表列出了所有的算术运算符。

表格中的实例假设整数变量A的值为10，变量B的值为20：

操作符 描述

+	加法 - 相加运算符两侧的值
-	减法 - 左操作数减去右操作数
*	乘法 - 相乘操作符两侧的值
/	除法 - 左操作数除以右操作数
%	取余 - 左操作数除以右操作数的余数
++	自增: 操作数的值增加1
- -	自减: 操作数的值减少1

例子

public static void main ( String [] args ) { int a = 10 ; int b = 20 ; int c = 25 ; int d = 25 ; System . out . println ( "a + b = " + ( a + b ) ); System . out . println ( "a - b = " + ( a - b ) ); System . out . println ( "a * b = " + ( a * b ) ); System . out . println ( "b / a = " + ( b / a ) ); System . out . println ( "b % a = " + ( b % a ) ); System . out . println ( "c % a = " + ( c % a ) ); System . out . println ( "a++ = " + ( a ++) ); System . out . println ( "a-- = " + ( a --) ); // 查看 d++ 与 ++d 的不同 System . out . println ( "d++ = " + ( d ++) ); System . out . println ( "++d = " + (++ d ) ); } 运行结果 "C:\Program Files\Java\jdk1.8.0_192\bin\java.exe" "-javaagent:C:\Program Files\JetBrains\IntelliJ IDEA 2020.1.3\lib\idea_rt.jar=51196:C:\Program Files\JetBrains\IntelliJ IDEA 2020.1.3\bin" - Dfile . encoding = UTF - 8 - classpath "C:\Program Files\Java\jdk1.8.0_192\jre\lib\charsets.jar;C:\Program Files\Java\jdk1.8.0_192\jre\lib\deploy.jar;C:\Program Files\Java\jdk1.8.0_192\jre\lib\ext\access-bridge-64.jar;C:\Program Files\Java\jdk1.8.0_192\jre\lib\ext\cldrdata.jar;C:\Program Files\Java\jdk1.8.0_192\jre\lib\ext\dnsns.jar;C:\Program Files\Java\jdk1.8.0_192\jre\lib\ext\jaccess.jar;C:\Program Files\Java\jdk1.8.0_192\jre\lib\ext\jfxrt.jar;C:\Program Files\Java\jdk1.8.0_192\jre\lib\ext\localedata.jar;C:\Program Files\Java\jdk1.8.0_192\jre\lib\ext\nashorn.jar;C:\Program Files\Java\jdk1.8.0_192\jre\lib\ext\sunec.jar;C:\Program Files\Java\jdk1.8.0_192\jre\lib\ext\sunjce_provider.jar;C:\Program Files\Java\jdk1.8.0_192\jre\lib\ext\sunmscapi.jar;C:\Program Files\Java\jdk1.8.0_192\jre\lib\ext\sunpkcs11.jar;C:\Program Files\Java\jdk1.8.0_192\jre\lib\ext\zipfs.jar;C:\Program Files\Java\jdk1.8.0_192\jre\lib\javaws.jar;C:\Program Files\Java\jdk1.8.0_192\jre\lib\jce.jar;C:\Program Files\Java\jdk1.8.0_192\jre\lib\jfr.jar;C:\Program Files\Java\jdk1.8.0_192\jre\lib\jfxswt.jar;C:\Program Files\Java\jdk1.8.0_192\jre\lib\jsse.jar;C:\Program Files\Java\jdk1.8.0_192\jre\lib\management-agent.jar;C:\Program Files\Java\jdk1.8.0_192\jre\lib\plugin.jar;C:\Program Files\Java\jdk1.8.0_192\jre\lib\resources.jar;C:\Program Files\Java\jdk1.8.0_192\jre\lib\rt.jar;D:\JavaProject\20210402\out\production\20210402" Test a + b = 30 a - b = - 10 a * b = 200 b / a = 2 b % a = 0 c % a = 5 a ++ = 10 a -- = 11 d ++ = 25 ++ d = 27 Process finished with exit code 0

关系运算符

运算符 描述

==	检查如果两个操作数的值是否相等，如果相等则条件为真。
！=	检查如果两个操作数的值是否相等，如果值不相等则条件为真。
>	检查左操作数的值是否大于右操作数的值，如果是那么条件为真。
<	检查左操作数的值是否小于右操作数的值，如果是那么条件为真
>=	检查左操作数的值是否大于或等于右操作数的值，如果是那么条件为真。
<=	检查左操作数的值是否小于或等于右操作数的值，如果是那么条件为真。

例子

public static void main ( String [] args ) { int a = 10 ; int b = 20 ; System . out . println ( "a == b = " + ( a == b ) ); System . out . println ( "a != b = " + ( a != b ) ); System . out . println ( "a > b = " + ( a > b ) ); System . out . println ( "a < b = " + ( a < b ) ); System . out . println ( "b >= a = " + ( b >= a ) ); System . out . println ( "b <= a = " + ( b <= a ) ); } 运行结果 "C:\Program Files\Java\jdk1.8.0_192\bin\java.exe" "-javaagent:C:\Program Files\JetBrains\IntelliJ IDEA 2020.1.3\lib\idea_rt.jar=51452:C:\Program Files\JetBrains\IntelliJ IDEA 2020.1.3\bin" - Dfile . encoding = UTF - 8 - classpath "C:\Program Files\Java\jdk1.8.0_192\jre\lib\charsets.jar;C:\Program Files\Java\jdk1.8.0_192\jre\lib\deploy.jar;C:\Program Files\Java\jdk1.8.0_192\jre\lib\ext\access-bridge-64.jar;C:\Program Files\Java\jdk1.8.0_192\jre\lib\ext\cldrdata.jar;C:\Program Files\Java\jdk1.8.0_192\jre\lib\ext\dnsns.jar;C:\Program Files\Java\jdk1.8.0_192\jre\lib\ext\jaccess.jar;C:\Program Files\Java\jdk1.8.0_192\jre\lib\ext\jfxrt.jar;C:\Program Files\Java\jdk1.8.0_192\jre\lib\ext\localedata.jar;C:\Program Files\Java\jdk1.8.0_192\jre\lib\ext\nashorn.jar;C:\Program Files\Java\jdk1.8.0_192\jre\lib\ext\sunec.jar;C:\Program Files\Java\jdk1.8.0_192\jre\lib\ext\sunjce_provider.jar;C:\Program Files\Java\jdk1.8.0_192\jre\lib\ext\sunmscapi.jar;C:\Program Files\Java\jdk1.8.0_192\jre\lib\ext\sunpkcs11.jar;C:\Program Files\Java\jdk1.8.0_192\jre\lib\ext\zipfs.jar;C:\Program Files\Java\jdk1.8.0_192\jre\lib\javaws.jar;C:\Program Files\Java\jdk1.8.0_192\jre\lib\jce.jar;C:\Program Files\Java\jdk1.8.0_192\jre\lib\jfr.jar;C:\Program Files\Java\jdk1.8.0_192\jre\lib\jfxswt.jar;C:\Program Files\Java\jdk1.8.0_192\jre\lib\jsse.jar;C:\Program Files\Java\jdk1.8.0_192\jre\lib\management-agent.jar;C:\Program Files\Java\jdk1.8.0_192\jre\lib\plugin.jar;C:\Program Files\Java\jdk1.8.0_192\jre\lib\resources.jar;C:\Program Files\Java\jdk1.8.0_192\jre\lib\rt.jar;D:\JavaProject\20210402\out\production\20210402" Test a == b = false a != b = true a > b = false a < b = true b >= a = true b <= a = false Process finished with exit code 0

逻辑运算符

操作符 描述

&&	称为逻辑与运算符。当且仅当两个操作数都为真，条件才为真。
ll	称为逻辑或操作符。如果任何两个操作数任何一个为真，条件为真。
！	称为逻辑非运算符。用来反转操作数的逻辑状态。如果条件为true，则逻辑非运算符将得到false

例子

public static void main ( String [] args ) { boolean a = true ; boolean b = false ; System . out . println ( "a && b = " + ( a && b )); System . out . println ( "a || b = " + ( a || b ) ); System . out . println ( "!(a && b) = " + !( a && b )); }

赋值运算符

赋值运算符 描述 例子

=	简单的赋值运算符，将右操作数的值赋给左侧操作数	C = A + B将把A + B得到的值赋给C
+ =	加和赋值操作符，它把左操作数和右操作数相加赋值给左操作数	C + = A等价于C = C + A
- =	减和赋值操作符，它把左操作数和右操作数相减赋值给左操作数	C - = A等价于C = C - A
* =	乘和赋值操作符，它把左操作数和右操作数相乘赋值给左操作数	C * = A等价于C = C * A
/ =	除和赋值操作符，它把左操作数和右操作数相除赋值给左操作数	C / = A，C 与 A 同类型时等价于 C = C / A
（％）=	取模和赋值操作符，它把左操作数和右操作数取模后赋值给左操作数	C％= A等价于C = C％A
<< =	左移位赋值运算符	C << = 2等价于C = C << 2
>> =	右移位赋值运算符	C >> = 2等价于C = C >> 2
＆=	按位与赋值运算符	C＆= 2等价于C = C＆2
^ =	按位异或赋值操作符	C ^ = 2等价于C = C ^ 2
l=	按位或赋值操作符	C l = 2等价于C = C

public static void main ( String [] args ) { int a = 10 ; int b = 20 ; int c = 0 ; c = a + b ; System . out . println ( "c = a + b = " + c ); c += a ; System . out . println ( "c += a = " + c ); c -= a ; System . out . println ( "c -= a = " + c ); c *= a ; System . out . println ( "c *= a = " + c ); a = 10 ; c = 15 ; c /= a ; System . out . println ( "c /= a = " + c ); a = 10 ; c = 15 ; c %= a ; System . out . println ( "c %= a = " + c ); c <<= 2 ; System . out . println ( "c <<= 2 = " + c ); c >>= 2 ; System . out . println ( "c >>= 2 = " + c ); c >>= 2 ; System . out . println ( "c >>= 2 = " + c ); c &= a ; System . out . println ( "c &= a = " + c ); c ^= a ; System . out . println ( "c ^= a = " + c ); c |= a ; System . out . println ( "c |= a = " + c ); } 运行结果为: c = a + b = 30 c += a = 40 c -= a = 30 c *= a = 300 c /= a = 1 c %= a = 5 c <<= 2 = 20 c >>= 2 = 5 c >>= 2 = 1 c &= a = 0 c ^= a = 10 c |= a = 10 Process finished with exit code 0

Java运算符优先级

类别 操作 关联性

后缀	() [] . (点操作符)	左到右
一元	expr++ expr–	从左到右
一元	++expr --expr + - ～ ！	从右到左
乘性	* /％	左到右
加性	+ -	左到右
移位	>> >>> <<	左到右
关系	> >= < <=	左到右
相等	== !=	左到右
按位与	＆	左到右
按位异或	^	左到右
按位或	l	左到右
逻辑与	&&	左到右
逻辑或	ll	左到右
条件	？：	从右到左
赋值	= + = - = * = / =％= >> = << =＆= ^ = l=	从右到左
逗号	，	左到右

总结

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原文链接：https://blog.csdn.net/qq_45859087/article/details/115399589

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