Java8新特性系列一：行为参数化
2021-04-12 21:25
标签：tco rgs main 优化 color 代码 lis lambda 一个 行为参数化主要是为了应对需求的变化，减少代码的变动冗余、变动，应对行为标准建模，方式可以为定义接口，下面以一个例子说明行为参数化的必要性 有一个Apple类，属性包括颜色、重量等，现在用户需求为：筛选出苹果重量>100的苹果，这个需求很简单，很容易想到的实现如下： 用户改变增加需求： 筛选出重量>100而且颜色为red的苹果，很容易想到的实现为增加一个实现方法，但是随着需求的增加，会增加N多筛选的方法，同时冗余代码 filterApples方法只能接受对象，所以必须把代码包裹在ApplePredicate对象里，因为通过一个实现了test方法的对象来传递布尔表达式 可用匿名内部类和Lambd改进 Java8新特性系列一：行为参数化 标签：tco rgs main 优化 color 代码 lis lambda 一个 原文地址：https://www.cnblogs.com/oxygenG/p/13352513.html1. 什么是行为参数化
2. 需求一
package lambdasinaction.chap1;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
/**
* @Author oxygen
* @Date 2020/7/20 0020
* @Version V1.0
**/
public class MyFilterApple {
public static void main(String[] args) {
List inventory = Arrays.asList(new Apple(100, "red"), new Apple(180, "green"));
List apple = findWeightGH100Apple(inventory);
}
private static List findWeightGH100Apple(List inventory) {
List result = new ArrayList();
for (Apple apple : inventory) {
if (apple.getWeight() > 100) {
result.add(apple);
}
}
return result;
}
public static class Apple {
private int weight = 0;
private String color = "";
public Apple(int weight, String color) {
this.weight = weight;
this.color = color;
}
public void setMethod&getMethod(...)
}
}
2. 需求二
private static List findWeightGH100Apple(List inventory) {
List result = new ArrayList();
for (Apple apple : inventory) {
if (apple.getWeight()>100 && "green".equals(apple.getColor())){
result.add(apple);
}
}
}
3. 改进一
3.1 定义接口传递行为
public interface ApplePredicate {
boolean test(Apple apple);
}
3.2 多个类实现具体的逻辑
/**
*过滤重量大于100而且颜色是红色的苹果
*/
public class AppleColorPredicate implements ApplePredicate {
@Override
public boolean test(Apple apple) {
return "red".equals(apple.getColor()) && apple.getWeight() > 100;
}
}
/**
* 过滤重量>150的苹果
*/
public class AppleHeavyWeightPredicate implements ApplePredicate {
@Override
public boolean test(Apple apple) {
return apple.getWeight() > 150;
}
}
3.3 定义实现方法
List inventory = Arrays.asList(new Apple(100, "red"), new Apple(180, "green"));
MyFilterApple.AppleColorPredicate p = new MyFilterApple().new AppleColorPredicate();
List apples = filterApples(inventory, p);
MyFilterApple.AppleHeavyWeightPredicate p2 = new MyFilterApple().new AppleHeavyWeightPredicate();
List apples1 = filterApples(inventory, p2);
private static List filterApples(List inventory, ApplePredicate p) {
List result = new ArrayList();
for (Apple apple : inventory) {
if (p.test(apple)) {
result.add(apple);
}
}
return result；
}
3. 改进二
List apples3 = filterApples(inventory, new ApplePredicate() {//匿名内部类优化
@Override
public boolean test(Apple apple) {
return apple.getWeight() > 150;
}
});
List apples3 = filterApples(inventory, apple -> apple.getWeight() > 100);//Lambda表达式优化