java - 为什么我的实时结果没有在 main 中更新？

Question

我正在制作一个货币跟踪器来跟踪比特币的实时值(value)。

如果我在它自己的 main 方法中运行“bitcoinlive”类，它会正确运行，但当我创建文件的实例时，它不会工作。我需要它来打印比特币的实时值(value)。

我尝试打印出变量“a53”，但我不知道我做得是否正确。 以下是 bitcoinlive 类的导入列表，因为它一直给我一条错误消息，并且在发布此内容时不允许将其作为代码的一部分。

public static void main(String[] args) {
    Dates d = new Dates();
    String s = d.getDate();
    System.out.println("Date is" + s);
    W3 mywallet = new W3();
    Bitcoinlive mybitcoinlive = new Bitcoinlive();
    L3 myledger = new L3();
    Scanner myscanner = new Scanner(System.in);
    double buy = 0.0;
    int choice = 0;
    double bitcoin = 4000;
    double USD = 20000;

    while (choice != 5) {
        System.out.println("Welcome! Enter a command. \n"
                + "Enter 1) Buy Bitcoin \n"
                + "Enter 2) Sell Bitcoin  \n"
                + "Enter 3) Print Balance \n"
                + "Enter 4) Print History \n"
                + "ENTER 5) Exit Program\n");
        choice = myscanner.nextInt();

        if (choice == 1) {
            System.out.println("How many? ");
            buy = myscanner.nextDouble();
            mywallet.add(buy);
            bitcoin = bitcoin * buy;
            USD = USD - bitcoin;

            myledger.save(s);

            System.out.println("you have bought:" + mywallet.numcoins);
            System.out.println(USD);
            System.out.println(mybitcoinlive.a53);
            bitcoin = 4000;

        } else if (choice == 2 && USD >= bitcoin) {
            System.out.println("How many?");

            buy = myscanner.nextDouble();
            mywallet.subtract(buy);
            System.out.println("you have sold:" + mywallet.numcoins);
            USD = USD + bitcoin;
            System.out.println(USD);
            bitcoin = 4000;
            myledger.save(s);

        } else if (choice == 3) {
            System.out.println("Balance:" + mywallet.numcoins);

        } else if (choice == 4) {
            System.out.println("Transaction history:  ");

            System.out.println("you have made" + myledger.getsize() + "transactions"
                    + d.getDate());

        } else if (choice == 5) {
            // exit
            break;

        } else if (choice == 7) {
            System.out.println(mybitcoinlive.price);
        }

    }

    System.out.println("Bye");

}

这是我单独的类(class)

public class Bitcoinlive {



    Double a53=0.0;
    double price;     

    Double get() {

        try {
            String urlcoincapeth13 = "https://api.coinmarketcap.com/v1/ticker/bitcoin/";
            Document docblocktradescoincapeth13 = Jsoup.parse(new URL(urlcoincapeth13).openStream(), "UTF-8", "", Parser.xmlParser());
            String a13 = docblocktradescoincapeth13.toString();
            int a23 = a13.indexOf("price_usd") + 13;
            int a33 = a13.indexOf("price_btc") - 4;
            String a43 = a13.substring(a23, a33);
            a53 = Double.parseDouble(a43);
        } catch (Exception e) {
            System.out.println("Error accessing bitcoin values");
        }

        return a53;
    }
}

Answer 1

您的类 Bitcoinlive 将价格存储在名为 a53 的字段中。您可以通过调用get()来更新此字段。但是，看起来您从未调用 get() - 您只是调用该字段:

System.out.println(mybitcoinlive.a53);

尝试将该行替换为:

System.out.println(mybitcoinlive.get());

或者先刷新一下:

mybitcoinlive.get();
System.out.println(mybitcoinlive.a53);