简述Java Error与Exception的区别。
Error是所有错误类的祖先类，Exception是所有异常类的祖先类。前者不是程序需要捕获与进行处理的，当Error发生时，程序会立即停止
简述异常处理的两种方式
这两种方式分别为声明抛出处理与程序捕获处理。而声明抛出处理又分为隐式声明抛出与显式声明抛出；程序捕获处理则分为非嵌套与嵌套。 隐式声明抛出：程序方法对这类异常不作任何声明抛出或者处理，直接交给调用该方法的地方处理，且程序并不会编译失败也不会对产生异常的代码给出提示。 显式声明抛出：显式地通过throws向上级抛出异常。例如public static void main(String args[]) throws IOExceprion; 程序捕获处理： 通过使用try - catch - [finally]语句块，用来对可能产生异常的代码产生的异常进行捕获，并根据其异常类型进行不同的操作。
选取RuntimeException类的五个子类，编写抛出并捕获上述子类异常的程序。
import java
.util
.EmptyStackException
;
import java
.util
.Stack
;
class A{
int v
= 6;
public int getV() {
return v
;
}
}
public class ExcpOp {
public static void Arithmetic() {
int a
= 6, b
= 0;
try{
int c
= a
/ b
;
} catch (ArithmeticException ae
) {
System
.out
.println(ae
.getClass().getName()+" has been throw");
} finally {
System
.out
.println("ArithmeticEp is over!\n");
}
}
public static void NullPointer() {
try {
A a
= null
;
a
.getV();
} catch (NullPointerException npe
) {
System
.out
.println(npe
.getClass().getName()+" has been throw");
} finally {
System
.out
.println("NullPointer is over！\n");
}
}
public static void EmptyStack() {
Stack s
= new Stack();
try{
s
.push(5);
s
.pop();
System
.out
.println("Pop 1");
s
.pop();
System
.out
.println("Pop 2");
} catch (EmptyStackException ese
) {
System
.out
.println(ese
.getClass().getName()+" has been throw");
} finally {
System
.out
.println("EmptyStack is over！\n");
}
}
public static void IndexOutOfBounds() {
int[] a
= new int[3];
for (int i
= 0; i
<3 ; i
++ ) {
a
[i
] = i
;
}
try{
System
.out
.println(a
[4]);
} catch (IndexOutOfBoundsException ioe
) {
System
.out
.println(ioe
.getClass().getName()+" has been throw");
} finally {
System
.out
.println("EmptyStack is over！\n");
}
}
public static void NegativeArraySize() {
try{
int[] a
= new int[-3];
} catch (NegativeArraySizeException nase
) {
System
.out
.println(nase
.getClass().getName()+" has been throw");
} finally {
System
.out
.println("NegativeArraySize is over！\n");
}
}
public static void main(String
[] args
) {
ExcpOp
.Arithmetic();
ExcpOp
.EmptyStack();
ExcpOp
.IndexOutOfBounds();
ExcpOp
.NegativeArraySize();
ExcpOp
.NullPointer();
}
}
仿照例7.9，自己定义一个异常类，并在某场景下抛出该异常对象。
public class MyException extends Exception{
MyException(String msg
) {
super(msg
);
}
public static void Throw(int a
) throws MyException
{
if(a ！
=123456) {
throw new MyException(" 错误 ");
}
}
public static void main(String
[] args
) {
int a
= 660;
try{
MyException
.Throw(a
);
} catch (MyException me
) {
me
.printStackTrace();
a
= 123456;
} finally {
System
.out
.println("此时 正确");
}
}
}
