为了说明什么是异常，现在就让我们先产生一个异常。(exam.java)异常，即Exception。当Java程序违反Java语言语义限制时，Java虚拟机向程序发出错误信号，就叫异常-To illustrate what is unusual, let us first create an exception. (Exam.java) exception, that Exception. When the Java program Java language semantics limit violation, Java Virtual Machine send the wrong signal to the program, called abnormal