throw Exception 抛异异常

   if(this.aop == null)throw new NullPointerException("aop is null");     if(method == null)throw new NullPointerException("method is null");    if(something==null)　　　　　  throw new NullPointerException();　　　　　else 　　 　　 　 return "something"; public Object sell(){           if(checkUser())             Object obj = new Object();                         return obj ;           }else{               throw new RuntimeException();           }       }  if (t == null) {throw new NullPointerException("something bad");}if (o == null) throw new NullPointerException(); 算术异常类：ArithmeticExecption空指针异常类：NullPointerException类型强制转换异常：ClassCastException数组负下标异常：NegativeArrayException数组下标越界异常：ArrayIndexOutOfBoundsException违背安全原则异常：SecturityException文件已结束异常：EOFException文件未找到异常：FileNotFoundException字符串转换为数字异常：NumberFormatException操作数据库异常：SQLException输入输出异常：IOException方法未找到异常：NoSuchMethodException