2.Pi的近似值
思路：水题，考察循环和Swing，按题目给的近似式去做就好了，感觉也没啥好说的..
噢对了有意思的是这个级数收敛极慢….运行结果：
右图是输入1000时的结果
代码语言：javascript复制/**
* @Title: b.java
* @Description: TODO
* @author 菱形继承
* @date 2020-03-31 03:19:34
*/
/**
* @ClassName: b
* @Description: TODO
* @author 菱形继承
* @date 2020-03-31 03:19:34
*/
import javax.swing.*;
public class b {
public static void main(String[] args) {
String user_input=JOptionPane.showInputDialog("please in put an Integer n:");
int check=Integer.parseInt(user_input);
double pi=0;
for(int j = 1;j <= check;j ){
pi =4* Math.pow(-1,j 1) / (2*j-1);
}
JOptionPane.showMessageDialog(null, "PI is approximately equal to: " pi);
}
}
