Scratch.java

gistfile1.txt

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.function.Function;
import java.util.stream.Stream;


class Scratch {

    public static void main(String[] args) {
       Function<String, String> first = Files.lines(Paths.get("test.txt")).map(e -> wrapFunction(Scratch::processLine)).toList();
       Stream<String> stringStream = Files.lines(Paths.get("test.txt")).map(wrapFunction(Scratch::processLine));
    }

    public static <T, R, E extends Exception> Function<T, R> wrapFunction(CheckedExceptionFunction<T, R, E> checkedExceptionFunction) {
        return t -> {
            try {
                return checkedExceptionFunction.apply(t);
            } catch (Exception e) {
                throw new RuntimeException(e);
            }
        };
    }

    private static String processLine(String line) throws IOException {
        if (line.equals("error")) {
            throw new IOException("エラーが発生しました");
        }
        return line.toUpperCase();
    }

    @FunctionalInterface
    interface CheckedExceptionFunction<T, R, E extends Exception> {
        R apply(T t) throws E;
    }
}