【设计模式-03】Strategy策略模式及应用场景

一、简要描述

• Java 官方文档

Overview (Java SE 18 & JDK 18)module indexhttps://docs.oracle.com/en/java/javase/18/docs/api/index.html

• Java中使用到的策略模式

Comparator、comparable

Comparator (Java SE 18 & JDK 18)declaration: module: java.base, package: java.util, interface: Comparatorhttps://docs.oracle.com/en/java/javase/18/docs/api/java.base/java/util/Comparator.html

Comparable (Java SE 18 & JDK 18)declaration: module: java.base, package: java.lang, interface: Comparablehttps://docs.oracle.com/en/java/javase/18/docs/api/java.base/java/lang/Comparable.html

二、主要设计思想

三、重新调整修改

1、定义支持泛型的Comparator比较器

/**
 * @description: 比较器接口
 * @author: flygo
 * @time: 2022/7/4 16:26
 */
public interface Comparator<T> {

  int compare(T o1, T o2);
}

2、调整Sorter排序类和方法

/**
 * @description: 排序对象
 * @author: flygo
 * @time: 2022/7/4 11:16
 */
public class Sorter<T> {

  public void sort(T[] arr, Comparator<T> comparator) {
    for (int i = 0; i < arr.length - 1; i++) {
      int minPos = i;
      for (int j = i + 1; j < arr.length; j++) {
        minPos = comparator.compare(arr[j], (arr[minPos])) == -1 ? j : minPos;
      }
      swap(arr, i, minPos);
    }
  }

  void swap(T[] arr, int i, int j) {
    T temp = arr[i];
    arr[i] = arr[j];
    arr[j] = temp;
  }
}

3、定义猫高度的比较器

/**
 * @description: 猫按高比较
 * @author: flygo
 * @time: 2022/7/4 16:29
 */
public class CatHeightComparator implements Comparator<Cat> {

  @Override
  public int compare(Cat o1, Cat o2) {
    if (o1.getHeight() < o2.getHeight()) return -1;
    else if (o1.getHeight() > o2.getHeight()) return 1;
    else return 0;
  }
}

4、定义猫重量的比较器

/**
 * @description: 猫按体重比较
 * @author: flygo
 * @time: 2022/7/4 16:29
 */
public class CatWeightComparator implements Comparator<Cat> {

  @Override
  public int compare(Cat o1, Cat o2) {
    if (o1.getWeight() > o2.getWeight()) return -1;
    else if (o1.getWeight() < o2.getWeight()) return 1;
    else return 0;
  }
}

5、主方法实现排序

import java.util.Arrays;

/**
 * @description: 主方法
 * @author: flygo
 * @time: 2022/7/4 11:15
 */
public class StrategyMain {

  public static void main(String[] args) {
    Cat[] arr = {new Cat(3, 3), new Cat(5, 5), new Cat(1, 1)};

    Sorter sorter = new Sorter();

    //    CatHeightComparator comparator = new CatHeightComparator();
    CatWeightComparator comparator = new CatWeightComparator();

    sorter.sort(arr, comparator);

    System.out.println(Arrays.toString(arr));
  }
}

四、Lambda表达式写法

1、Comparator 接口定义为 @FunctionalInterface

/**
 * @description: 比较器接口
 * @author: flygo
 * @time: 2022/7/4 16:26
 */
@FunctionalInterface
public interface Comparator<T> {

  int compare(T o1, T o2);
}

2、Lambda表达式调用方式

import java.util.Arrays;

/**
 * @description: 主方法
 * @author: flygo
 * @time: 2022/7/4 11:15
 */
public class StrategyMain {

  public static void main(String[] args) {
    method2();
  }

  private static void method2() {
    Cat[] arr = {new Cat(3, 3), new Cat(5, 5), new Cat(1, 1)};

    Sorter<Cat> sorter = new Sorter();

    //    CatHeightComparator comparator = new CatHeightComparator();
    CatWeightComparator comparator = new CatWeightComparator();

    sorter.sort(
        arr,
        (o1, o2) -> {
          if (o1.getHeight() < o2.getHeight()) return -1;
          else if (o1.getHeight() > o2.getHeight()) return 1;
          else return 0;
        });

    System.out.println(Arrays.toString(arr));
   }
 }

五、源码地址

GitHub - jxaufang168/Design-Patterns: 设计模式学习设计模式学习. Contribute to jxaufang168/Design-Patterns development by creating an account on GitHub.https://github.com/jxaufang168/Design-Patterns