// Demonstrate a method reference to an instance method
// A functional interface for string operations.
interface StringFunc {
    String func(String n);
}
// Now, this class defines an instance method called strReverse().
class MyStringOps {
    String strReverse(String str) {
        String result = "";
        int i;
        for (i = str.length()-1; i >= 0; i--) {
            result += str.charAt(i);
        }
        return result;
    }
}
class MethodRefDemo2 {
    // This method has a functional interface as the type of
    // its first parameter. Thus, it can be passed any instance
    // of that interface, including method references.
    static String stringOp(StringFunc sf, String s) {
        return sf.func(s);
    }
    public static void main(String args[])
    {
        String inStr = "Lambdas add power to Java";
        String outStr;
        // Create a MyStringOps object.
        MyStringOps strOps = new MyStringOps( );
        // Now, a method reference to the instance method strReverse
        // is passed to stringOp().
        outStr = stringOp(strOps::strReverse, inStr);
        System.out.println("Original string: " + inStr);
        System.out.println("String reversed: " + outStr);
    }
}