counter.java

Java网络编程与分布式计算, 主要分析java网络各方面的编程, 提供许多实用安全

// Chapter 7, Listing 6
public class Counter 
{
	private int countValue;

	public Counter()
	{
		countValue = 0;
	}

	public Counter(int start)
	{
		countValue = start;
	}

	// Synchronized method to increase counter
	public synchronized void increaseCount()
	{
		int count = countValue;

		// Simulate slow data processing and modification
		// Removing the synchronized keyword will demonstrate
		// how inaccurate concurrent access can be. Adjusting
		// this value may be necessary on faster machines.
		try
		{
			Thread.sleep(5);
		}
		catch (InterruptedException ie) {}

		count = count + 1;

		countValue = count;
	}

	// Synchronized method to return counter value
	public synchronized int getCount()
	{
		return countValue;
	}
}