To convert a String to Integer here we use Integer::valueOf method.
It is a method reference of Function in java 8.
The valueOf(String s, int radix) is an inbuilt method which returns an Integer object.
Here we implement convert method of Convertor interface.
Now convert method take String parameter and call from con reference which call valueOf method.
After converting String to Integer Object and store in Integer value parameter.
Now print the value.
@FunctionalInterface
interface Convertor {
T convert(F from);
}
public class TestStream {
public static void main(String[] args) {
Convertor con = Integer::valueOf;
Integer value = con.convert("123");
System.out.println(value);
}
}