我已经用jsf创建了一个货币转换器bean，我很难弄清楚如何修改 convert() 要设置的方法 targetCurrency 以外币和 targetAmount 以美元为单位。到目前为止，我掌握的情况如下：

@ManagedBean(name = "currMB")
@RequestScoped
public class Currency {
    // Currency conversion factors as or 10/21/2019
    private static final double CAN = 1.3128;
    private static final double EUR = 0.8957;
    private static final double JPN = 108.41;
    private static final double UK = 0.7701;

    public String name;
    public String currencyType;
    public double amount;

    public Currency() { }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getCurrencyType() {
        return currencyType;
    }

    public void setCurrencyType(String currencyType) {
        this.currencyType = currencyType;
    }

    public double getAmount() {
        return amount;
    }

    public void setAmount(double amount) {
        this.amount = amount;
    }

    public String convert() {
        double targetAmount = 0.0;
        String targetCurrency = null;
        String result = "Cannot calculate conversion";
        if (amount > 0.0) {

            targetAmount = CAN;
            targetAmount = EUR;
            targetAmount = JPN;
            targetAmount = UK;

        }
        if (targetCurrency != null && name != null) {
            result = String.format("%.2f US Dollars is %.2f %s", 
                    amount,targetAmount,targetCurrency);
        }
        return result;
    }

}

谢谢你的帮助