Gangmax Blog

A Java Code Sample of High Order

The code below shows how to convert a code repetition into a simplified abstraction with high order function implementation. At the first glance, this might be unnecessary. However as the code lines increase, such abstractions will make the code neat and short.

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import org.apache.commons.lang3.tuple.Triple;

import java.util.ArrayList;
import java.util.List;
import java.util.function.BiConsumer;
import java.util.function.Function;

public class Actions {

    public static void get(String path, Function<String, String> handler) {
        System.out.println("get path = " + path);
        System.out.println("get handler result = " + handler.apply(path));
    }

    public static void post(String path, Function<String, String> handler) {
        System.out.println("post path = " + path);
        System.out.println("post handler result = " + handler.apply(path));
    }

    public static void main(String[] args) {
        // The original code.
        runPlainOld();
        // The updated code.
        List<Triple<BiConsumer<String, Function<String, String>>, String, Function<String, String>>>  triples = new ArrayList<>();
        triples.add(Triple.of(Actions::get, "/running", name -> name));
        triples.add(Triple.of(Actions::get, "/:taskId", jobId -> "taskId=" + jobId));
        triples.add(Triple.of(Actions::post, "/sayhello", name -> "Hello, " + name));
        runHighOrder(triples);
    }

    public static void runPlainOld() {
        get("/running", name -> name);
        get("/:taskId", jobId -> "taskId=" + jobId);
        post("/sayhello", name -> "Hello, " + name);
    }
    public static void runHighOrder(List<Triple<BiConsumer<String, Function<String, String>>, String, Function<String, String>>>  triples) {
        for (Triple<BiConsumer<String, Function<String, String>>, String, Function<String, String>> triple : triples) {
            triple.getLeft().accept(triple.getMiddle(), triple.getRight());
        }
    }
}

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