Functional Interface Method reference

Question

I am new to java 8 and trying this. i have an interface

public interface CurrencyRateDao{
    Double getCurrencyRate(String srcCur,String tarCur, int month);
}

Accessing using it this way :

CurrencyRateDao currencyRateDao = new CurrencyRateDaoImpl();
Double rate = ('USD','INR',1) -> currencyRateDao::getCurrencyRate;

Giving an error:

target type of this expression must be a functional interface.

Please suggest what is wrong with above code

Naman · Accepted Answer · 2019-03-04 09:55:09Z

3

You simply need

Double rate = currencyRateDao.getCurrencyRate("USD", "INR", 1);

If you were to represent the interface as a lambda, it would look like :

CurrencyRateDao currencyRateDao = (srcCur, tarCur, month) -> Double.MAX_VALUE;
// accepts three arguments and returns a Double value

answered Mar 4, 2019 at 9:55

Naman

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