Question

java 保留小数点后2位

/**
* Write a description of class Cylinder here.
*
* @author (your name)
* @version (a version number or a date)
*/
public class Cylinder
{
// instance variables - replace the example below with your own
private double radius;
private double height;

/**
* Constructor for objects of class Cylinder
*/
public Cylinder(double r, double h)
{
// initialise instance variables
radius = r;
height = h;

double newBase = base();
System.out.println(" the value of the base is: " + newBase);
double newCirc = circumference();
System.out.println(" the value of the Circ is: " + newCirc);
}
public double base()
{
double answer= Math.PI * radius * radius;

return answer;
}
public double circumference()
{
double answer=Math.PI * radius;
return answer;
}
}

保留2位小数

Answer 1

给你说个比较简单的方法吧，不知道你有没用学过c语言，c和c++都有格式化输出函数：printf()。
Java也有同样的格式化输出，针对你的这个问题可以这么写
System.out.printf("%.2f",d);//d是一个double或float类型，保留小数点后两位
这只是printf的某一种用法，建议你去看看它的其他更多的用法。

Answer 2

DecimalFormat df = new DecimalFormat("0.00");
double d = 123.9078;
double db = df.format(d);
则db=123.90；