Java中Math.PI就表示π。其源码为public static final double PI = 3.14159265358979323846。
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比如说你要算半径为2的圆的面积，代码如下：
double pi=Math.PI
int r=2
double S=pi*r*r
运行结果如下图
扩展资料
package 计算π的近似值;
import java.util.Scanner;
public class Example1 {
public static void main(String[] args) {
Scanner scan=new Scanner(System.in);
System.out.println("请输入精度：");
double z=scan.nextDouble();
System.out.println("在精度为"+z+"的条件下，π约等于：\n"+jishuPI(z));
}
static double jishuPI(double z){
double sum=2;
int n=1;
int m=3;
double t=2;
while(tz){
t=t*n/m;
sum=sum+t;
n++;
m+=2;
}
return sum;
}
}
参考资料：Java官网 API-Class Math
public class Test {
/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
getPi(10000);
getPi(20000);
}
//输入迭代次数
static void getPi(int n) {
float pi = 0;
for(int i = 1;i=n;i++) {
if(i%2==1) {
pi = pi + (float)1/(2*i-1);
}else {
pi = pi - (float)1/(2*i-1);
}
}
System.out.println("n="+n+";π="+4*pi);
}
}
#includestdio.h
main()
{ int n,i; double t,
sum;/*1*/
printf("请输入n的值\n");
scanf("%d",n);
sum=2; i=1; t=2;/*2*/
while(in) { t=t*(2*i)*(2*i)/(2*i-1)/(2*i+1);
/*3*/ // sum=sum*t; i=i+1; }
printf("π的值=%f\n",t);/*4*/ }
或。
写一个Java程序来实现蒙特卡洛法求π的近似值：
import java.io.BufferedReader;
import java.io.InputStreamReader;
public class MonteCarloPi {
public static void main(String[] args) throws Exception{
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
System.out.print("How many darts shoud I toss at the board?\n");
String s = br.readLine();
int numberOfDarts = Integer.parseInt(s.trim());
double radius = 1.0;
Dartboard d = new Dartboard(radius);
for(int i=1; i=numberOfDarts; i++){
Toss t = Toss.getRandom(radius);
d.strike(t);
}
double fractionIn = d.getFractionIn();
double pi = 4.0 * fractionIn;
System.out.println("Pi is approximately "+pi);
}
}
class Dartboard{
private double radius;
private int insideCircle, outsideCircle;
public Dartboard(double radius){
this.radius = radius;
insideCircle = 0;
outsideCircle = 0;
}
public void strike(Toss toss){
double x = toss.getX();
double y = toss.getY();
if(Math.sqrt(x*x + y*y) radius)
insideCircle++;
else
outsideCircle++;
}
public double getFractionIn() {
double total = (double) (insideCircle + outsideCircle);
return (double) insideCircle/total;
}
}
class Toss{
private double x,y;
public Toss(double x, double y){
this.x = x;
this.y = y;
}
public double getX(){return x;}
public double getY(){return y;}
public static Toss getRandom(double radius){
double x,y;
double size = Math.random();
double sign = Math.random();
size = size * radius;
if(sign 0.5)
x = size;
else
x = -size;
size = Math.random();
sign = Math.random();
size = size * radius;
if(sign 0.5)
y = size;
else
y = -size;
return new Toss(x,y);
}
}
扩展资料：
C语言:用循环结构分别编写程序
#include
void main()
{
\x09int n=1;
\x09float temp;
\x09float sum=0;
\x09do
\x09{
\x09\x09temp=(float)1/(2*n-1);
\x09\x09if(n%2==1)
\x09\x09\x09sum+=temp;
\x09\x09else
\x09\x09\x09sum-=temp;
\x09\x09n++;
\x09}while(temp=0.000001);
\x09printf("Pi=%f\n",sum*4);
}
