题目一：请阅读并运行AboutException.java示例
AboutException.java
1 import javax.swing.JOptionPane;
2
3 public class AboutException {
4 public static void main(String[] args) {
5 int i=1,j=0,k;
6 k=i/j;
7
8 try {
9 k=i/j;//Causes division-by-zero exception
10 //throw new Exception("Hello.Exception!");
11 }catch(ArithmeticException e) {
12 System.out.println("被0除."+e.getMessage());
13 }catch(Exception e) {
14 if(e instanceof ArithmeticException) {
15 System.out.println("被0除");
16 }else {
17 System.out.println(e.getMessage());
18 }
19 }finally {
20 JOptionPane.showConfirmDialog(null, "OK");
21 }
22 }
23 }
运行结果：
题目二：阅读以下代码（CatchWho.java）
CatchWho.java
1 public class CatchWho {
2 public static void main(String[] args) {
3 try{
4 try{
5 throw new ArrayIndexOutOfBoundsException();
6 }catch(ArrayIndexOutOfBoundsException e) {
7 System.out.println( "ArrayIndexOutOfBoundsException" + "/内层try-catch");
8 }
9 throw new ArithmeticException();
10 }catch(ArithmeticException e){
11 System.out.println("发生ArithmeticException");
12 }catch(ArrayIndexOutOfBoundsException e){
13 System.out.println("ArrayIndexOutOfBoundsException" + "/外层try-catch");
14 }
15 }
16 }
执行结果：
CatchWho2.java
1 public class CatchWho2 {
2 public static void main(String[] args){
3 try{
4 try{
5 throw new ArrayIndexOutOfBoundsException();
6 }catch(ArithmeticException e) {
7 System.out.println( "ArrayIndexOutOfBoundsException" + "/内层try-catch");
8 }
9 throw new ArithmeticException();
10 } catch(ArithmeticException e) {
11 System.out.println("发生ArithmeticException");
12 }catch(ArrayIndexOutOfBoundsException e){
13 System.out.println( "ArrayIndexOutOfBoundsException" + "/外层try-catch");
14 }
15 }
16 }
执行结果：
题目三：请先阅读 EmbedFinally.java示例，再运行它，观察其输出并进行总结。
EmbedFinally.java
1 public class EmbededFinally {
2 public static void main(String[] args) {
3 int result;
4 try {
5 System.out.println("in Level 1");
6 try {
7 System.out.println("in Level 2");
8 //result=100/0;//Level 2
9 try {
10 System.out.println("in Level 3");
11 result=100/0;//Level
12 }catch(Exception e) {
13 System.out.println("Level 3:"+e.getClass().toString());
14 }finally {
15 System.out.println("In Level 3 finally");
16 }
17 //result=100/0;//Level 2
18 }catch(Exception e) {
19 System.out.println("Level 2:"+e.getClass().toString());
20 }finally {
21 System.out.println("In Level 2 finally");
22 }
23 //result=100/0;//Level 1
24 }catch(Exception e) {
25 System.out.println("Level 1:"+e.getClass().toString());
26 }finally {
27 System.out.println("In Level 1 finally");
28 }
29 }
30 }
执行结果为：
将result的表达式换在第二个try里面，其执行代码为：
1 public class EmbededFinally {
2 public static void main(String[] args) {
3 int result;
4 try {
5 System.out.println("in Level 1");
6 try {
7 System.out.println("in Level 2");
8 result=100/0;//Level 2
9 try {
10 System.out.println("in Level 3");
11 //result=100/0;//Level
12 }catch(Exception e) {
13 System.out.println("Level 3:"+e.getClass().toString());
14 }finally {
15 System.out.println("In Level 3 finally");
16 }
17 //result=100/0;//Level 2
18 }catch(Exception e) {
19 System.out.println("Level 2:"+e.getClass().toString());
20 }finally {
21 System.out.println("In Level 2 finally");
22 }
23 //result=100/0;//Level 1
24 }catch(Exception e) {
25 System.out.println("Level 1:"+e.getClass().toString());
26 }finally {
27 System.out.println("In Level 1 finally");
28 }
29 }
30 }
执行结果为：
将result的表达式换在第一个try里面，其执行代码为：
1 public class EmbededFinally {
2 public static void main(String[] args) {
3 int result;
4 try {
5 System.out.println("in Level 1");
6 try {
7 System.out.println("in Level 2");
8 //result=100/0;//Level 2
9 try {
10 System.out.println("in Level 3");
11 //result=100/0;//Level
12 }catch(Exception e) {
13 System.out.println("Level 3:"+e.getClass().toString());
14 }finally {
15 System.out.println("In Level 3 finally");
16 }
17 //result=100/0;//Level 2
18 }catch(Exception e) {
19 System.out.println("Level 2:"+e.getClass().toString());
20 }finally {
21 System.out.println("In Level 2 finally");
22 }
23 result=100/0;//Level 1
24 }catch(Exception e) {
25 System.out.println("Level 1:"+e.getClass().toString());
26 }finally {
27 System.out.println("In Level 1 finally");
28 }
29 }
30 }
执行结果为：
总结：
在try..catch...finally语句中，try里面的是率先执行的，若是try内的语句有错误，catch中的语句才会执行，若是无错误，便会执行finally内的语句。
题目四：辨析：finally语句块一定会执行吗？ 请通过 SystemExitAndFinally.java示例程序回答上述问题
SystemExitAndFinally.java
1 public class SystemExitAndFinally {
2 public static void main(String[] args){
3 try{
4 System.out.println("in main");
5 throw new Exception("Exception is thrown in main");
6 //System.exit(0);
7 }catch(Exception e){
8 System.out.println(e.getMessage());
9 System.exit(0);
10 }finally{
11 System.out.println("in finally");
12 }
13 }
14 }
执行结果为：
若程序改为：
则会出现以下错误：
结论：finally代码块不一定会被执行
