java 通过行为参数化传递代码，来解决不断增长的需求
1， 通过定义不同的谓词接口来区分不同的苹果的重量，如果后续有更多的需求，只需要添加更多的谓词即可package org.example;
import java.util.ArrayList;
import java.util.List;
enum Color {
RED, GREEN, YELLOW
}
class Apple {
private Integer weight;
private Color color;
public Apple(Integer weight, Color color) {
this.weight = weight;
this.color = color;
}
public Integer getWeight() {
return weight;
}
public void setWeight(Integer weight) {
this.weight = weight;
}
public Color getColor() {
return color;
}
public void setColor(Color color) {
this.color = color;
}
}
interface ApplePredicate {
boolean test(Apple apple);
}
class AppleGreenColorPredicate implements ApplePredicate {
// 选择绿色苹果的谓词
@Override
public boolean test(Apple apple) {
return Color.GREEN.equals(apple.getColor());
}
}
class AppleHeavyWeightPredicate implements ApplePredicate {
// 选择重量大于150克的谓词
@Override
public boolean test(Apple apple) {
return apple.getWeight() > 150;
}
}
public class Main {
public static List<Apple> filterApples(List<Apple> inventory, ApplePredicate p) {
// 通过谓词筛选苹果
List<Apple> result = new ArrayList<>();
for (Apple apple :
inventory) {
if (p.test(apple)) {
result.add(apple);
}
}
return result;
}
public static void main(String[] args) {
List<Apple> inventory = new ArrayList<>();
inventory.add(new Apple(300,Color.RED));
inventory.add(new Apple(12,Color.RED));
inventory.add(new Apple(350,Color.GREEN));
inventory.add(new Apple(200,Color.YELLOW));
// 方便的筛选绿色苹果和重苹果
List<Apple> result = filterApples(inventory, new AppleGreenColorPredicate());
result = filterApples(result, new AppleHeavyWeightPredicate());
for (var apple :
result) {
System.out.println(apple.getColor() + ":" + apple.getWeight());
}
}
}2，上述定义接口实现的方式过于啰嗦和繁杂可以使用匿名类和lamble表达式进行简化
2.1， 匿名内部类
List<Apple> result = filterApples(inventory, new ApplePredicate() {
@Override
public boolean test(Apple apple) {
return Color.GREEN.equals(apple.getColor());
}
});
result = filterApples(inventory, new ApplePredicate() {
@Override
public boolean test(Apple apple) {
return apple.getWeight() > 150;
}
});2.2 lamble表达式
List<Apple> result = filterApples(inventory, (Apple apple)->apple.getColor().equals(Color.GREEN));
result = filterApples(result, (Apple apple)->apple.getWeight()>150);3,更进一步的可以将针对苹果的list类型进行抽象化，用于其他的水果
interface Predicate <T>{
boolean test(T t);
}
public static <T> List<T> filter(List<T> inventory, Predicate<T> p) {
// 通过谓词筛选T
List<T> result = new ArrayList<>();
for (T e :
inventory) {
if (p.test(e)) {
result.add(e);
}
}
return result;
}
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