浅析设计模式2 —— 策略模式

//step1:定义抽象策略角色（Strategy）：所有促销活动的共同接口
public interface Strategy {  
    void show();
}
//step2:定义具体策略角色（Concrete Strategy）：不同类型的具体促销策略
//618大促活动 A
public class ConcreteStrategyA implements Strategy{
    @Override
    public void show() {
        System.out.println("618大促");
    }
}
//99大促活动 B
public class ConcreteStrategyB implements Strategy{
    @Override
    public void show() {
        System.out.println("99大促");
    }
}
//双11大促活动 C
public class ConcreteStrategyC implements Strategy{
    @Override
    public void show() {
        System.out.println("双11大促");
    }
}
//step3:定义环境角色（Context）：把促销活动推送给用户，这里可理解为淘宝平台
public class Context_TaoPlatform{
    //持有抽象策略的引用
    private Strategy myStrategy;
    //生成构造方法，让平台根据传入的策略参数选择策略
    public TaoPlatform(Strategy strategyType) {
        this.myStrategy = strategyType;
    }
    //向用户展示促销活动
    public void taoPlatformShow(String time) {
        System.out.println(time + "的促销策略是:");
        myStrategy.show();
    }
}
//step4:客户端调用
public class StrategyPattern{
  public static void main(String[] args){
        Context_TaoPlatform context;
        String time1 = "9月";
        Strategy strategyB = new ConcreteStrategyB();
        context = new Context_TaoPlatform(strategyB);
        context.taoPlatformShow(time1);
        String time2 = "11月";
        Strategy strategyC = new ConcreteStrategyC();
        context = new Context_TaoPlatform(strategyC);
        context.taoPlatformShow(time2);
        String time3 = "6月";
        Strategy strategyA = new ConcreteStrategyA();
        context = new Context_TaoPlatform(strategyA);
        context.taoPlatformShow(time3);
  }   
}

9月的促销策略是：
99大促
11月的促销策略是：
双11大促
6月的促销策略是：
618大促

public class Context_TaoPlatform{
    //持有抽象策略的引用
    private Strategy myStrategy;
    //生成构造方法，让平台根据传入的策略参数选择促销活动
    public TaoPlatform(Strategy strategyType) {
        this.myStrategy = strategyType;
    }
    //向用户展示促销活动
    public void taoPlatformShow(String time) {
        System.out.println(time + "的促销策略是:");
        myStrategy.show();
    }
}

public class Factory{
    public static Shirt exhibit(String ShirtName){
        switch(ShirtName){
            case "女款衬衫":
                return new WomenShirt();
            case "男款衬衫":
                return new MenShirt();
            default:
                return null;
        }
    }
}

public class Arrays{
    public static <T> void sort(T[] a, Comparator<? super T> c) {
        if (c == null) {
            //若没有传入Comparator接口的实现类对象，调用默认的升序排序方法
            sort(a);
        } else {
            if (LegacyMergeSort.userRequested)
                //jdk5及之前的传统归并排序，新版本中LegacyMergeSort.userRequested默认false
                legacyMergeSort(a, c);
            else
                //改进后的归并排序
                TimSort.sort(a, 0, a.length, c, null, 0, 0);
        }
    }
}

public class demo {
    public static void main(String[] args) {
        Integer[] data = {2, 0, 22, 14, 1, 3, 4};
        // 实现降序排序
        Arrays.sort(data, new Comparator<Integer>() {
             // 排序策略 降序
            public int compare(Integer o1, Integer o2) {
                return o2 - o1;
            }
        });
        System.out.println(Arrays.toString(data)); 
    }
}

class TimSort<T> {
    static <T> void sort(T[] a, int lo, int hi, Comparator<? super T> c,
                         T[] work, int workBase, int workLen) {
        assert c != null && a != null && lo >= 0 && lo <= hi && hi <= a.length;
        int nRemaining  = hi - lo;
        if (nRemaining < 2)
            return;  
        if (nRemaining < MIN_MERGE) {
            int initRunLen = countRunAndMakeAscending(a, lo, hi, c);
            binarySort(a, lo, hi, lo + initRunLen, c);
            return;
        }
        ...
    }   
    private static <T> int countRunAndMakeAscending(T[] a, int lo, int hi,Comparator<? super T> c) {
        assert lo < hi;
        int runHi = lo + 1;
        if (runHi == hi)
            return 1;
        if (c.compare(a[runHi++], a[lo]) < 0) { 
            while (runHi < hi && c.compare(a[runHi], a[runHi - 1]) < 0)
                runHi++;
            reverseRange(a, lo, runHi);
        } else {                              
            while (runHi < hi && c.compare(a[runHi], a[runHi - 1]) >= 0)
                runHi++;
        }
        return runHi - lo;
    }
}