运算符

运算符

算数运算符

public class dome6 {
    //常量 final 修饰符，不存在先后顺序
    static final double ip = 3.12;
    //常量  常量 变量     

    public static void main(String[] args) {
        System.out.println(ip);//3.12
        long a = 1000000000l;
        int b = 10;
        short c = 10;
        byte d = 10;
        double e = 3.12;
        System.out.println(a+b+c);//long
        System.out.println(c+d+e);//23.12    double
        System.out.println(b+c+d);//30   为int
        
        
        
        
        
        public class Dome007 {
    public static void main(String[] args) {

        //++  --   一元运算符  自增  自减
        //int a = 5;
        //int b = a++;
        //System.out.println(a);//a++ 执行完代码后  先给b附值再自增   6
        //System.out.println(b);//5
        //int a = 5;
        //int b = ++a;
        //System.out.println(a);//6
        //System.out.println(b);//6    ++a执行代码前，先自增  后给b赋值
        int a = 5;
        int b = a--;
        System.out.println(a);//4
        System.out.println(b);//5
        int c = 5;
        int d = --c;
        System.out.println(c);//4
        System.out.println(d);//4
 三元运算符   条件运算符  //x ? y :z 必须掌握
           //如果x为真结果为y   反之为z
     public class Dome10 {
     public static void main(String[] args) {
        int rbq = 60;
        String type = rbq<70 ?"及格":"不及格";
        System.out.println(type);

a + b = 30    10   20
a - b = -10
a * b = 200
b / a = 2
b % a = 0
c % a = 5
a++   = 10
a--   = 11
d++   = 25
++d   = 27

a = 000101
b = 100001
a&b = 000001   俩一为1其余取0
a|b = 100101   俩0取0其余为一
a^b = 111011   对位相同为零 否则为一
~a = 111010     零变一  一变0

面试题

怎么计算2*8

2*2*2*2
位运算  效率极高
<<左移相当于*2   >>右移相当于/2
System out printin(2<<3)

字符串连接符

 int b = 30;
 int a = 10;
String 字符串
System.out.println(""+a+b);//1030
System.out.println(+a+b"" );//40

image-20210416110200853](C:\Users\dell\AppData\Roaming\Typora\typora-user-images\image-20210416110200853.png)

public class Dome8 {
    public static void main(String[] args) {
        double pow = Math.pow(2, 3);
        double pow1 = Math.pow(3, 2);

        System.out.println(pow);
        System.out.println(pow1)；
        //与&&   或||  非！


//短路运算
        int a = 4;
        boolean c = (a<4)&&(a++<4);
        System.out.println(a);//4
        System.out.println(c);//执行完a<4判断出来就不执行了  false

    }
}