1.throws的应用:
1).定义方法时,以后调用此方法,需要进行try-catch语句处理.
2).如果对语句不希望处理try-catch语句,以用throw进行抛出.
2.异常的处理结构:
try-catch-finally
3.自定义异常类
必须继承Exception
4.在自定义位置需要写明:throws Exception
catch语句为if-else结构.只匹配第一个.所以放置顺序很重要.
finnally,不管try是否发生作用,它均会执行.即使在之前遇到return语句. 如果希望它不执行,需要遇到system.exit(0)语句.
5.
例如
try
...
{if(x<0)throw new Xxxexception("xxx");else throw new Yyyexception("yyy");}
catch
(Xxxexception e)
...
{..}
catch
(Yyyexception e)
...
{...}
6.在类的继承时,子类throw的异常必须事父类异常的子异常,不能throw新的异常.只能比父类的少,不能比父类的多.
附例:自定义异常.
class
Test
...
{ public int divide(int x,int y) throws myException,Exception ...{ if(y<0) throw new myException("y is minus"+y); int result; result=x/y; return result; }}
class
myException
extends
Exception
...
{ public myException (String msg) ...{ super(msg); }}
public
class
ByZero
...
{ public static void main(String[] args) ...{ try ...{ new Test().divide(3,-9); } catch(myException e) ...{ System.out.println(e.getMessage()); //返回字符串 e.printStackTrace(); //返回详细信息 } catch(Exception e) ...{ System.out.println(e.getMessage()); } System.out.println("he"); }}
