example0502_myexception.java

本程序用来说明如何自定义异常

import java.io.*;

//本程序用来说明如何自定义异常，以及如何使用自定义的异常
public class Example0502_MyException
{
	public Example0502_MyException()
	{
		try
		{
			String nstr = "20";
			System.out.println("The data is: " + nstr);
			
			int n = Integer.parseInt(nstr);
			
			testException(n);
		}
		catch (NumberFormatException e)
		{
			System.out.println("catch NumberFormatException: " + e.getMessage());
		}
		catch (MyException e)
		{
			System.out.println("catch MyException: " + e.getMessage());
		}
	}
	
	//声明抛出异常的方法
	public void testException(int n) throws MyException
	{
		if (n < 15)
		{
			throw new MyException("Invalid number: n < 15");
		}
		
		if (n > 25)
		{
			throw new MyException("Invalid number: n > 25");
		}
	}
	
	//声明一个一般的方法，不抛出异常
	public void func()
	{
	}
	
	public static void main(String[] args)
	{
		new Example0502_MyException();
	}
}

//自定义异常类
class MyException extends Exception
{
	public MyException()
	{
	}
	
	public MyException(String message)
	{
		super(message);
	}
}

//此类用于测试子类方法不能抛出比起超类方法更多的异常
class SubclassMethod extends Example0502_MyException
{
	public void testException(int n) throws MyException//, IOException
	{
	}
	
	public void func()// throws Exception
	{
	}
}