单例

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import java.util.ArrayList;
import java.util.Random;

class Singleton
{
/**
* Singleton
*
*/
@SuppressWarnings("finally")
public static boolean Init()
{
        boolean bRet = false;
        try
        {
      synchronized(Singleton.class)
      {
       if( null == m_pSingleton)
       {
        m_pSingleton = new Singleton();
        bRet = true;
       }
      }
        }
        catch (Exception e)
        {
            System.out.println("Singleton Init, catch exception");
            m_pSingleton = null;
            throw e;
        }
        finally
        {
            return bRet;
        }
}
public static void UnInit()
{
  synchronized(Singleton.class)
  {
   if( null != m_pSingleton)
   {//释放空闲资源
    m_pSingleton = null;
   }
  }
}
public static Singleton GetInstance()
{
  synchronized(Singleton.class)
  {
   return m_pSingleton;
  }
}
public void doSomething()
{}
private Singleton()
{}
private static Singleton m_pSingleton = null;
}

class MultiObj
{
private static final int SIZE_OBJ = 4;
private static ArrayList<MultiObj> m_vpTcpIp = null;
@SuppressWarnings("finally")
public static boolean Init()
{
        boolean bRet = false;
        try
        {
         synchronized(Singleton.class)
      {
       if( null == m_vpTcpIp)
       {
        m_vpTcpIp = new ArrayList<MultiObj>();
        for(int i=0; i<SIZE_OBJ; i++)
        {
         MultiObj pMultiObj = new MultiObj(i);
         m_vpTcpIp.add(pMultiObj);
         pMultiObj = null;
        }
        bRet = true;
       }
      }
  }
        catch (Exception e)
        {
            System.out.println("Singleton Init, catch exception");
            m_vpTcpIp = null;
            throw e;
        }
        finally
        {
            return bRet;
        }
}
public static void UnInit()
{
  synchronized(Singleton.class)
  {
   if( null != m_vpTcpIp)
   {//释放空闲资源
    m_vpTcpIp.clear();
    m_vpTcpIp = null;
   }
  }
}
public static MultiObj GetInstance()
{
  Random pRandom = new Random();
  MultiObj pMultiObj = m_vpTcpIp.get(pRandom.nextInt(SIZE_OBJ));
  pRandom = null;
  return pMultiObj;
}
public MultiObj(int i)
{
  m_iID = i;
  System.out.println("MultiObj");
}
void doSomething()
{
  System.out.println(m_iID);
};
private int m_iID;
}

//---------------------------------------------------

class SingletonClient
{
public static void Client()
{
  MultiObj.Init();
  for(int i=0; i<20; i++)
  {
   MultiObj pMultiObj = MultiObj.GetInstance();
   pMultiObj.doSomething();
   pMultiObj = null;
  }
  MultiObj.UnInit();
}
}