package com.itranswarp.learnjava;
/**
* for练习
*/
public class Main {
public static void main(String[] args) {
System.out.println("------------first---------------");
int[] ns = { 1, 4, 9, 16, 25 };
for (int i=ns.length-1; i>=0; i--) {
System.out.println(ns[i]);
}
System.out.println("------------second------------");
int sum = 0;
for (int i=0; i<ns.length; i++) {
sum += ns[i];
}
System.out.println(sum);
System.out.println("------------third------------");
double pi = 0;
// for (int i=1; i > 0; i += 4) {
// pi += (double)1/i;
// }
// for (int i=3; i > 0; i += 4) {
// pi -= (double)1/i;
// }
for (int i=1; i > 0; i += 2) {
if (i == 1) {
pi += (double)1/i;
} else if (i == 3) {
pi -= (double)1/i;
} else if (i%4 == 1) {
pi += (double)1/i;
} else if (i%4 == 3) {
pi -= (double)1/i;
}
}
pi = pi*4;
System.out.println(pi);
}
}
xiao伟iii