1、如何定义自己的异常
Java支持自己创建的异常。了解异常看这里：什么是java中的异常
方法如下：
1、所有的异常必须是Throwable的子类。
2、如果想写一个检查异常，需要扩展Exception类。
3、如果想编写一个运行时异常，则需要扩展RuntimeException类。
4、异常类与任何其他类一样，可以包含字段和方法。
我们可以定义如下自己的异常处理类：
- class MyException extends Exception{
- }
例子：
- import java.io.*;
-
- public class InsufficientFundsException extends Exception
- {
- private double amount;
- public InsufficientFundsException(double amount)
- {
- this.amount = amount;
- }
- public double getAmount()
- {
- return amount;
- }
- }
为了证明我们的使用用户定义的异常，下面的CheckingAccount类包含一个withdraw()方法抛出一个InsufficientFundsException。
- import java.io.*;
-
- public class CheckingAccount
- {
- private double balance;
- private int number;
- public CheckingAccount(int number)
- {
- this.number = number;
- }
- public void deposit(double amount)
- {
- balance += amount;
- }
- public void withdraw(double amount) throws
- InsufficientFundsException
- {
- if(amount <= balance)
- {
- balance -= amount;
- }
- else
- {
- double needs = amount - balance;
- throw new InsufficientFundsException(needs);
- }
- }
- public double getBalance()
- {
- return balance;
- }
- public int getNumber()
- {
- return number;
- }
- }
下面BankDemo程序演示调用deposit()和withdraw() 方法。
- public class BankDemo
- {
- public static void main(String [] args)
- {
- CheckingAccount c = new CheckingAccount(101);
- System.out.println("Depositing $500...");
- c.deposit(500.00);
- try
- {
- System.out.println("
- Withdrawing $100...");
- c.withdraw(100.00);
- System.out.println("
- Withdrawing $600...");
- c.withdraw(600.00);
- }catch(InsufficientFundsException e)
- {
- System.out.println("Sorry, but you are short $"
- + e.getAmount());
- e.printStackTrace();
- }
- }
- }
编译所有上述三个文件并运行BankDemo，这将产生以下结果：
Depositing 500...Withdrawing100...
Withdrawing 600...Sorry,butyouareshort200.0
InsufficientFundsException
at CheckingAccount.withdraw(CheckingAccount.java:25)
at BankDemo.main(BankDemo.java:13)
原文地址：
http://blog.csdn.net/ooppookid/article/details/51106457
