有没有办法重构这些 if 语句？

Question

只是想知道是否有重构以下代码的方法？我是 Java 的新手，正在尝试使用 DRY 代码 - 下面是我写的，但似乎有很多条件需要检查

void printDirection() {
  if (yDirection > 0) {
    if (xDirection < 0) {
      println("Travelling South-West");
    } else {
      println("Travelling South-East");
    }
  } else if (yDirection < 0) {
    if (xDirection <0) {
      println("Travelling North-West");
    } else {
      println("Travelling North-East");
    }
  }
}

在此先感谢您的帮助！

Answer 1

您可以分别评估 north/south 和 east/west 条件，并将说明粘贴到您的消息中。

System.out.printf("Travelling %s-%s%n", (yDirection < 0 ? "North" : "South"),
                  (xDirection < 0 ? "West" : "East"));

根据你问题中的代码，我假设你只关心这四个互补方向（不是正北、正东、静止等）。

Answer 2

如果你真的想让它变干，可以使用运算符 ?但它既不容易阅读也不推荐。它用于以尽可能快的速度为目标的编程竞赛。

它遵循以下方案：（条件？WhatHappenIfConditionIsTrue：WhatHappenIfConditionIsFalse）；您可以在作业中使用它：

int i = (a>0)?a:0;

在那种情况下，如果a>0则i=a，否则a=0

在你的情况下，我会这样做

void printDirection()
{
    System.out.println("Travelling " + (yDirection > 0?"South":"North") + "-" + (xDirection>0?"East":"West"));
}

Answer 3

一些建议： 1. 由于x,y组合；有五个州；您可以使用枚举类型来定义这些状态； 2. 如果你想减少代码中的if...else语句，请参考Status Machine Design Pattern；不过我觉得，在你的情况下，状态就这么简单，没必要搞得太复杂

public class Status {

    public enum Direction {
        SOUTH_WEST((x, y) -> y > 0 && x < 0, "Travelling South-West")
        , SOUTH_EAST((x, y) -> y >0 && x > 0, "Travelling South-East")
        , NORTH_EAST((x, y) -> x > 0 && y < 0, "Travelling North-East")
        , NORTH_WEST((x,y) -> x < 0 && y < 0, "Travelling North-West"), CENTER((x,y) -> x == 0 && y == 0, "");

        BiPredicate<Integer, Integer> bp;
        String desc;

        public BiPredicate<Integer, Integer> getBp() {
            return bp;
        }
        public void setBp(BiPredicate<Integer, Integer> bp) {
            this.bp = bp;

        }

        public String getDesc() {
            return desc;
        }
        public void setDesc(String desc) {
            this.desc = desc;
        }
        private Direction(BiPredicate<Integer, Integer> bp, String desc) {
            this.bp = bp;
            this.desc = desc;
        }
        public static Direction getDirection(int x, int y) {
            for (Direction direction : Direction.values()) {
                if(direction.getBp().test(x, y)) {
                    return direction;
                }
            }
            return null;
        }
    }

    public static void main(String[] args) {
        Direction d =  Direction.getDirection(3, 4);
        System.out.println(d.getDesc());
        /*      if(d == Direction.SOUTH_WEST){
                    System.out.println("do some thing");
                } else if(d == Direction.SOUTH_EAST){
                    System.out.println("do some thing");
                } else if(d == Direction.NORTH_EAST){
                    System.out.println("do some thing");
                } else if(d == Direction.NORTH_WEST){
                    System.out.println("do some thing");
                }*/
    }
}

有没有办法重构这些 if 语句？

Is there a way to refactor these if statements?

java

refactoring

if-statement

conditional-statements