java程序：set改造成map

逻辑：

      set是无序不重复数据元素的集合。

      map是另一种set，如果将<key,value>看成一个整体的话，其实就是set。在map中，若用map的keyset()方法将key提取出来，便构成了一个set集合。

      所以，就定义一个整体SimpleEntry<K,V>作为元素存入set。

代码：

/*

*SimpleEntry<K,V>作为map对象的存储元素

*/

class SimpleEntry<K, V> 
  implements Map.Entry<K, V>, Serializable 
{

// map中的key不可变 
  private final K key; 
  private V value;

  public SimpleEntry(K paramK, V paramV) 
  { 
    this.key = paramK; 
    this.value = paramV; 
  }

public SimpleEntry(Map.Entry<? extends K, ? extends V> paramEntry) 
  { 
    this.key = paramEntry.getKey(); 
    this.value = paramEntry.getValue(); 
  }

  public K getKey() 
  { 
    return this.key; 
  }

  public V getValue() 
  { 
    return this.value; 
  }

  public V setValue(V paramV) 
  { 
    Object localObject = this.value; 
    this.value = paramV; 
    return localObject; 
  }

  public boolean equals(Object paramObject) 
  { 
    if (paramObject == this) 
    { 
      return true; 
    } 
    if (paramObject.getClass() == SimpleEntry.class) 
    { 
      SimpleEntry localSimpleEntry = (SimpleEntry)paramObject; 
      return localSimpleEntry.getKey().equals(getKey()); 
    } 
    return false; 
  }

  public int hashCode() 
  { 
    return this.key == null ? 0 : this.key.hashCode(); 
  }

  public String toString() 
  { 
    return this.key + "=" + this.value; 
  } 
}

/*

*Set2Map<K, V>继承自hashset，底层是利用hashset来存储，但存储的是<K，V>这样的二元组，所以可以看成是一个map

*/

public class Set2Map<K, V> extends HashSet<SimpleEntry<K, V>> 
{ 
  public void clear() 
  { 
    super.clear(); 
  }

  public boolean containsKey(K paramK) 
  { 
    return super.contains(new SimpleEntry(paramK, null)); 
  }

  boolean containsValue(Object paramObject) 
  { 
    for (SimpleEntry localSimpleEntry : this) 
    { 
      if (localSimpleEntry.getValue().equals(paramObject)) 
      { 
        return true; 
      } 
    } 
    return false; 
  }

  public V get(Object paramObject) 
  { 
    for (SimpleEntry localSimpleEntry : this) 
    { 
      if (localSimpleEntry.getKey().equals(paramObject)) 
      { 
        return localSimpleEntry.getValue(); 
      } 
    } 
    return null; 
  }

  public V put(K paramK, V paramV) 
  { 
    add(new SimpleEntry(paramK, paramV)); 
    return paramV; 
  }

//内部用了迭代器实现

  public void putAll(Map<? extends K, ? extends V> paramMap) 
  { 
    for (Iterator localIterator = paramMap.keySet().iterator(); localIterator.hasNext(); ) { Object localObject = localIterator.next();

      add(new SimpleEntry(localObject, paramMap.get(localObject))); 
    } 
  }

//内部用了迭代器实现

  public V removeEntry(Object paramObject) 
  { 
    Iterator localIterator = iterator(); 
    while (localIterator.hasNext()) 
    { 
      SimpleEntry localSimpleEntry = (SimpleEntry)localIterator.next(); 
      if (localSimpleEntry.getKey().equals(paramObject)) 
      { 
        Object localObject = localSimpleEntry.getValue(); 
        localIterator.remove(); 
        return localObject; 
      } 
    } 
    return null; 
  }

  public int size() 
  { 
    return super.size(); 
  } 
}

测试程序：

public class Set2MapTest 
{ 
  public static void main(String[] paramArrayOfString) 
  { 
    Set2Map localSet2Map = new Set2Map();

    localSet2Map.put("语文", Integer.valueOf(89)); 
    localSet2Map.put("数学", Integer.valueOf(83)); 
    localSet2Map.put("英文", Integer.valueOf(80)); 
    System.out.println(localSet2Map);

    System.out.println(localSet2Map.size()); 
    localSet2Map.removeEntry("数学"); 
    System.out.println("删除key为\"数学\"的Entry之后：" + localSet2Map);

    System.out.println("语文成绩：" + localSet2Map.get("语文"));

    System.out.println("是否包含\"英文\"key :" + localSet2Map.containsKey("英文"));

    System.out.println("是否包含 82 value :" + localSet2Map.containsValue(Integer.valueOf(82)));

    localSet2Map.clear(); 
    System.out.println("执行clear()方法之后的集合：" + localSet2Map); 
  } 
}

 本文转自二郎三郎博客园博客，原文链接：http://www.cnblogs.com/haore147/p/4214803.html，如需转载请自行联系原作者