新手了解java基础知识(二)

：：0 ：2021-10-27 22:52:55

目录
算数运算符
例子
关系运算符
例子
逻辑运算符
例子
赋值运算符
Java运算符优先级
总结
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 FilesJavajdk1.8.0_192binjava.exe" "-javaagent:C:Program FilesJetBrainsIntelliJ IDEA 2020.1.3libidea_rt.jar=51196:C:Program FilesJetBrainsIntelliJ IDEA 2020.1.3bin" -Dfile.encoding=UTF-8 -classpath "C:Program FilesJavajdk1.8.0_192jrelibcharsets.jar;C:Program FilesJavajdk1.8.0_192jrelibdeploy.jar;C:Program FilesJavajdk1.8.0_192jrelibextaccess-bridge-64.jar;C:Program FilesJavajdk1.8.0_192jrelibextcldrdata.jar;C:Program FilesJavajdk1.8.0_192jrelibextdnsns.jar;C:Program FilesJavajdk1.8.0_192jrelibextjaccess.jar;C:Program FilesJavajdk1.8.0_192jrelibextjfxrt.jar;C:Program FilesJavajdk1.8.0_192jrelibextlocaledata.jar;C:Program FilesJavajdk1.8.0_192jrelibextnashorn.jar;C:Program FilesJavajdk1.8.0_192jrelibextsunec.jar;C:Program FilesJavajdk1.8.0_192jrelibextsunjce_provider.jar;C:Program FilesJavajdk1.8.0_192jrelibextsunmscapi.jar;C:Program FilesJavajdk1.8.0_192jrelibextsunpkcs11.jar;C:Program FilesJavajdk1.8.0_192jrelibextzipfs.jar;C:Program FilesJavajdk1.8.0_192jrelibjavaws.jar;C:Program FilesJavajdk1.8.0_192jrelibjce.jar;C:Program FilesJavajdk1.8.0_192jrelibjfr.jar;C:Program FilesJavajdk1.8.0_192jrelibjfxswt.jar;C:Program FilesJavajdk1.8.0_192jrelibjsse.jar;C:Program FilesJavajdk1.8.0_192jrelibmanagement-agent.jar;C:Program FilesJavajdk1.8.0_192jrelibplugin.jar;C:Program FilesJavajdk1.8.0_192jrelibresources.jar;C:Program FilesJavajdk1.8.0_192jrelibrt.jar;D:JavaProject20210402outproduction20210402" 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 FilesJavajdk1.8.0_192binjava.exe" "-javaagent:C:Program FilesJetBrainsIntelliJ IDEA 2020.1.3libidea_rt.jar=51452:C:Program FilesJetBrainsIntelliJ IDEA 2020.1.3bin" -Dfile.encoding=UTF-8 -classpath "C:Program FilesJavajdk1.8.0_192jrelibcharsets.jar;C:Program FilesJavajdk1.8.0_192jrelibdeploy.jar;C:Program FilesJavajdk1.8.0_192jrelibextaccess-bridge-64.jar;C:Program FilesJavajdk1.8.0_192jrelibextcldrdata.jar;C:Program FilesJavajdk1.8.0_192jrelibextdnsns.jar;C:Program FilesJavajdk1.8.0_192jrelibextjaccess.jar;C:Program FilesJavajdk1.8.0_192jrelibextjfxrt.jar;C:Program FilesJavajdk1.8.0_192jrelibextlocaledata.jar;C:Program FilesJavajdk1.8.0_192jrelibextnashorn.jar;C:Program FilesJavajdk1.8.0_192jrelibextsunec.jar;C:Program FilesJavajdk1.8.0_192jrelibextsunjce_provider.jar;C:Program FilesJavajdk1.8.0_192jrelibextsunmscapi.jar;C:Program FilesJavajdk1.8.0_192jrelibextsunpkcs11.jar;C:Program FilesJavajdk1.8.0_192jrelibextzipfs.jar;C:Program FilesJavajdk1.8.0_192jrelibjavaws.jar;C:Program FilesJavajdk1.8.0_192jrelibjce.jar;C:Program FilesJavajdk1.8.0_192jrelibjfr.jar;C:Program FilesJavajdk1.8.0_192jrelibjfxswt.jar;C:Program FilesJavajdk1.8.0_192jrelibjsse.jar;C:Program FilesJavajdk1.8.0_192jrelibmanagement-agent.jar;C:Program FilesJavajdk1.8.0_192jrelibplugin.jar;C:Program FilesJavajdk1.8.0_192jrelibresources.jar;C:Program FilesJavajdk1.8.0_192jrelibrt.jar;D:JavaProject20210402outproduction20210402" 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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