详解Java编程中的策略模式

public class Context {
  //持有一个具体策略的对象
  private Strategy strategy;
  /**
   * 构造函数，传入一个具体策略对象
   * @param strategy  具体策略对象
   */
  public Context(Strategy strategy){
    this.strategy = strategy;
  }
  /**
   * 策略方法
   */
  public void contextInterface(){
    
    strategy.strategyInterface();
  }
  
}

public interface Strategy {
  /**
   * 策略方法
   */
  public void strategyInterface();
}

public class ConcreteStrategyA implements Strategy {

  @Override
  public void strategyInterface() {
    //相关的业务
  }

}
public class ConcreteStrategyB implements Strategy {

  @Override
  public void strategyInterface() {
    //相关的业务
  }

}
public class ConcreteStrategyC implements Strategy {

  @Override
  public void strategyInterface() {
    //相关的业务
  }

}

  import java.util.*; 
   
  public class TestComparator { 
    public static void main(String args[]) { 
      LinkedList<String> list = new LinkedList<String>(); 
      list.add("wangzhengyi"); 
      list.add("bululu"); 
       
      // 创建一个逆序比较器 
      Comparator<String> r = Collections.reverseOrder(); 
       
      // 通过逆序比较器进行排序 
      Collections.sort(list, r); 
       
      System.out.println(list); 
    } 
  } 

  public static <T> void sort(List<T> list, Comparator<? super T> c) { 
    Object[] a = list.toArray(); 
    Arrays.sort(a, (Comparator)c); 
    ListIterator i = list.listIterator(); 
    for (int j=0; j<a.length; j++) { 
      i.next(); 
      i.set(a[j]); 
    } 
  } 

  public static <T> void sort(T[] a, Comparator<? super T> c) { 
    if (LegacyMergeSort.userRequested) 
      legacyMergeSort(a, c); 
    else 
      TimSort.sort(a, c); 
  } 


  static <T> void sort(T[] a, Comparator<? super T> c) { 
    sort(a, 0, a.length, c); 
  } 


  /** To be removed in a future release. */ 
  private static <T> void legacyMergeSort(T[] a, Comparator<? super T> c) { 
    T[] aux = a.clone(); 
    if (c==null) 
      mergeSort(aux, a, 0, a.length, 0); 
    else 
      mergeSort(aux, a, 0, a.length, 0, c); 
  } 

  private static void mergeSort(Object[] src, 
                 Object[] dest, 
                 int low, int high, int off, 
                 Comparator c) { 
    int length = high - low; 
   
    // Insertion sort on smallest arrays 
    if (length < INSERTIONSORT_THRESHOLD) { 
      for (int i=low; i<high; i++) 
        for (int j=i; j>low && c.compare(dest[j-1], dest[j])>0; j--) 
          swap(dest, j, j-1); 
      return; 
    } 
   
    // Recursively sort halves of dest into src 
    int destLow = low; 
    int destHigh = high; 
    low += off; 
    high += off; 
    int mid = (low + high) >>> 1; 
    mergeSort(dest, src, low, mid, -off, c); 
    mergeSort(dest, src, mid, high, -off, c); 
   
    // If list is already sorted, just copy from src to dest. This is an 
    // optimization that results in faster sorts for nearly ordered lists. 
    if (c.compare(src[mid-1], src[mid]) <= 0) { 
      System.arraycopy(src, low, dest, destLow, length); 
      return; 
    } 
   
    // Merge sorted halves (now in src) into dest 
    for(int i = destLow, p = low, q = mid; i < destHigh; i++) { 
      if (q >= high || p < mid && c.compare(src[p], src[q]) <= 0) 
        dest[i] = src[p++]; 
      else 
        dest[i] = src[q++]; 
    } 
  } 

  // If list is already sorted, just copy from src to dest. This is an 
  // optimization that results in faster sorts for nearly ordered lists. 
  if (c.compare(src[mid-1], src[mid]) <= 0) { 
    System.arraycopy(src, low, dest, destLow, length); 
    return; 
  } 

  public interface Comparator<T> { 
    int compare(T o1, T o2); 
  } 

  public int compare(Comparable<Object> c1, Comparable<Object> c2) { 
     return c2.compareTo(c1); 
  }