sample11_17.java

Java SE 6.0前11章示的示例代码,简单易学

package wyf.jc;
//声明自定义异常类
class MyExceptionToHighLevel extends Exception
{
	//定义MyExceptionToHighLevel类的两个构造器
	public MyExceptionToHighLevel()
	{	}
	public MyExceptionToHighLevel(String msg)
	{
		super(msg);
	}
}
class MyExceptionFromLowLevel extends Exception
{
	//定义MyExceptionFromLowLevel类的两个构造器
	public MyExceptionFromLowLevel()
	{	}
	public MyExceptionFromLowLevel(String msg)
	{
		super(msg);
	}
}
//执行业务的类
class MyClass
{
	public void doLowLevelStaff(int a) throws MyExceptionFromLowLevel
	{
		//执行判断
          if(a>50) 
          {//正常情况
          	System.out.println("恭喜你，低层方法执行成功！！！");
          }
          else
          {//不正常情况，抛出异常
          	System.out.println("低层发生事故，上报！！！");
          	throw new MyExceptionFromLowLevel("值不大于50，发生事故！！！");
          }
	}
	//定义doMiddleLevelStaff方法将抛出MyExceptionToHighLevel异常
	public void doMiddleLevelStaff() throws MyExceptionToHighLevel
	{
		//受监视的代码
		try
		{
			int value=(int)Math.round(Math.random()*100);
			System.out.println("调用值为："+value+"。");
			this.doLowLevelStaff(value);
		}
		//异常处理代码
		catch(MyExceptionFromLowLevel e)
		{
			System.out.println("发生事故，中层先进行一些处理，然后上报到上层！！！");
			//再次抛出异常
			throw new MyExceptionToHighLevel("有事故发生，请上层处理！！！");
		}
	}
	//定义doHighLevelStaff方法
	public void doHighLevelStaff()
	{
		//受监视的代码
		try
		{
			this.doMiddleLevelStaff();
		}
		//异常处理代码
		catch(MyExceptionToHighLevel e)
		{
			System.out.println("上层最终处理事故！！！");
		}
	}	
}
public class Sample11_17
{
	public static void main(String[] args)
	{
		//创建MyClass对象
         MyClass mc=new MyClass();
		//调用doHighLevelStaff方法
         mc.doHighLevelStaff();
	}
}