Math

运算

/**
 * Created by KebabShell
 * on 2020/3/28 上午 10:41
 */
public class MathTest {
    @Test
    public void test(){
        double result = Math.sqrt(4);
        System.out.println("sqrt result:" + result);//开方
        result = Math.pow(4, 2);
        System.out.println("pow result:" + result);//4的2次方
        int i = Math.floorMod(5, 2);//5 % 2
        System.out.println("i:" + i);
        long round = Math.round(1.5);
        System.out.println("round:" + round);//四舍五入

        System.out.println("up:" + Math.ceil(4.000000001));//向上取整
        System.out.println("floor:" + Math.floor(4.99999));//向下取整
    }
    @Test
    public void leftMove(){
        int result = 3 << 2;
        System.out.println("<<:" + result);//左移一位都相当于乘以2的1次方，左移n位就相当于乘以2的n次方
    }
    @Test
    public void rightMove(){
        int result = 12 >> 2;
        System.out.println(">>:" + result);//右移n位相当于除以2的n次方
    }
}

大数：

/**
 * Created by KebabShell
 * on 2020/3/29 下午 04:50
 */
public class BigDecimalTest {
    @Test
    public void test(){
        //浮点型直接运算会失真
        System.out.println(1.1 + 2.2);

        double a = 1.1;
        double b = 2.2;

        //不要new
        BigDecimal bigDecimal = BigDecimal.valueOf(a);
        BigDecimal bigDecimal1 = BigDecimal.valueOf(b);

        BigDecimal add = bigDecimal.add(bigDecimal1);
        System.out.println(add);

        //        bigDecimal.divide()  除法
        //        bigDecimal.subtract()  减法
        //        bigDecimal.multiply()  乘法

        //最终拿到double的数据
        double value = bigDecimal.doubleValue();


        int compare = Double.compare(1.1, 6.3);//比较
    }
}