How to declare method's return type the as return type of last lambda in array passed to the method

Question

I ask for something which I see impossible and I\'ll delete question if it is.

I have got method:

public Object convertBy(Function... functions) {
}
         


        

Answer 1

Thank all of you who elaborated on the subject, your solutions are much better in real world.

As the author I would like to post my solution that enabled not changing the invocations of convertBy() int the main() one bit. It is very short and ugly, but works.

Main:

Function> flines ... lambda here

Function, String> join ... lambda here

Function> collectInts ... lambda here

Function, Integer> sum ... lambda here


String fname = System.getProperty("user.home") + "/LamComFile.txt"; 
InputConverter fileConv = new InputConverter<>(fname);
List lines = fileConv.convertBy(flines);
String text = fileConv.convertBy(flines, join);
List ints = fileConv.convertBy(flines, join, collectInts);
Integer sumints = fileConv.convertBy(flines, join, collectInts, sum);

System.out.println(lines);
System.out.println(text);
System.out.println(ints);
System.out.println(sumints);

List arglist = Arrays.asList(args);
InputConverter> slistConv = new InputConverter<>(arglist);  
sumints = slistConv.convertBy(join, collectInts, sum);
System.out.println(sumints); 

The InputConverter class:

public class InputConverter {

    private T value;

    public InputConverter(T value) {
        this.value = value;
    }

    public  R convertBy(Function... functions) {
        Object result = value;
        for (int i = 0; i < functions.length; i++) {
            result = functions[i].apply(result);
        }
        return (R) result;
    }
}