小编Bas*_*uga的帖子

请帮助我如何使用 bitpay API 将价格从比特币转换为美元。我写了下面的代码，但我得到了美元到比特币的价格。我想要比特币到美元的价格。谢谢！

<?php  
    $url = "https://bitpay.com/api/rates";

    $json = file_get_contents($url);
    $data = json_decode($json, TRUE);

    $rate = $data[1]["rate"];    
    $usd_price = 10;     # Let cost of elephant be 10$

    $bitcoin_price = round( $usd_price / $rate , 8 );
?>

我正在使用GMP包来实现两个函数的产品,我将其表达为两个收敛系列的柯西产品.

更详细:我正在寻找一种计算指数函数f(x)=g(x)*h(x)在哪里的方法,g(x)并且h(x)是一种特殊的超几何函数(见下文),两者都表示为系列.

我的问题是,这是有效的,并且与我自己的近似和wolframalpha的结果一致x<29,但是没有成功x>29.在实践中,我需要约值x=10^6.

我使用的3个公式如下图所示:

代码

void invfak(mpf_t invn, unsigned int n) //Calculates inverse factorial, !/n!
{
        unsigned int i;
        mpf_t k;

        mpf_init_set_d(k,1.0);
        mpf_init_set_d(invn,0.0);
        i=2;

        for (i = 2; i <= n; ++i) {
            mpf_mul_ui(k, k, i);
        }

        mpf_ui_div(invn,1.0,k);
        mpf_clear(k);
}

 void E2F2E(mpf_t result, long double x, unsigned int N)
{
        mpf_t Q1,Q2;          ///gives Nth term in series expansion of exp(x)

        mpf_init_set_d(Q1,x);
        mpf_init_set_d(Q2,0.0);
        mpf_init_set_d(result,0.0);

        mpf_pow_ui(Q1,Q1,N); /// Q1=Q1^N=x^N
        invfak(Q2,N);       /// …

我创建了两个类,我试图从'UserInterface'类中获取用户的值,但我希望它存储在我的第二个名为'Calculator'的类中.

import java.util.Scanner;

public class UserInterface {

    public static void main (String Args[]) {
        Calculator calculator = new Calculator();
        Scanner input = new Scanner(System.in);
        System.out.println("Enter your first value: \t");
        input.nextInt(firstValue);
        System.out.println("Enter your second value: \t");
        input.nextInt(secondValue);
    }
}

我想input.nextInt(firstValue); 将值传递给firstValue,它位于下面显示的'calculator'类中.

public class Calculator {

    public int firstValue;
    public int secondValue;

    public Calculator(int firstValue, int secondValue) {
        this.firstValue = firstValue;
        this.secondValue = secondValue;         
    }
}

提前致谢.

我正在尝试将文件写入Java中的特定目录.我已经在Stack Overflow论坛中查看了许多与此相关的问题.然而,我尝试的每种方法最终都会出现此错误:

java.io.IOException: No such file or directory
at java.io.UnixFileSystem.createFileExclusively(Native Method)
at java.io.File.createNewFile(File.java:1012)
at mainFiles.fileManagers.NewCSV.nJSON(NewCSV.java:40)
at mainFiles.appWindows.UserDashboard$1.run(UserDashboard.java:30)
at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:311)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:756)
at java.awt.EventQueue.access$500(EventQueue.java:97)
at java.awt.EventQueue$3.run(EventQueue.java:709)
at java.awt.EventQueue$3.run(EventQueue.java:703)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:80)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:726)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)

码:

public static void nJSON(String username) { 

    File file = new File("src/jsonFiles/" +  username + ".json");

    try {
        if (file.exists() && file.isDirectory()) {
            System.out.println(username + ".json exist.");
        } else {
            json.put("Username", username); 
            json.put("Password", mainFiles.windowsSrc.UserInfo.password); …