一、动手动脑：多层的异常捕获-1
阅读以下代码（CatchWho.java），写出程序运行结果：
public class CatchWho {
public static void main(String[] args) {
try {
try {
throw new ArrayIndexOutOfBoundsException();
}
catch(ArrayIndexOutOfBoundsException e) {
System.out.println( "ArrayIndexOutOfBoundsException" + "/内层try-catch");
}
throw new ArithmeticException();
}
catch(ArithmeticException e) {
System.out.println("发生ArithmeticException");
}
catch(ArrayIndexOutOfBoundsException e) {
System.out.println( "ArrayIndexOutOfBoundsException" + "/外层try-catch");
}
}
}
运行结果：
ArrayIndexOutOfBoundsException/内层try-catch
发生ArithmeticException
二、动手动脑：多层的异常捕获-2
阅读以下代码（CatchWho2.java），写出程序运行结果：
public class CatchWho2 {
public static void main(String[] args) {
try {
try {
throw new ArrayIndexOutOfBoundsException();
}
catch(ArithmeticException e) {
System.out.println( "ArrayIndexOutOfBoundsException" + "/内层try-catch");
}
throw new ArithmeticException();
}
catch(ArithmeticException e) {
System.out.println("发生ArithmeticException");
}
catch(ArrayIndexOutOfBoundsException e) {
System.out.println( "ArrayIndexOutOfBoundsException" + "/外层try-catch");
}
}
}
运行结果：
ArrayIndexOutOfBoundsException/外层try-catch
三、请先阅读 EmbededFinally.java示例，再运行它，观察其输出并进行总结。
public class EmbededFinally {
public static void main(String args[]) {
int result;
try {
System.out.println("in Level 1");
try {
System.out.println("in Level 2");
// result=100/0; //Level 2
try {
System.out.println("in Level 3");
result=100/0; //Level 3
}
catch (Exception e) {
System.out.println("Level 3:" + e.getClass().toString());
}
finally {
System.out.println("In Level 3 finally");
}
// result=100/0; //Level 2
}
catch (Exception e) {
System.out.println("Level 2:" + e.getClass().toString());
}
finally {
System.out.println("In Level 2 finally");
}
// result = 100 / 0; //level 1
}
catch (Exception e) {
System.out.println("Level 1:" + e.getClass().toString());
}
finally {
System.out.println("In Level 1 finally");
}
}
}
运行结果：
in Level 1
in Level 2
in Level 3
Level 3:class java.lang.ArithmeticException
In Level 3 finally
In Level 2 finally
In Level 1 finally
分析：当有多层嵌套的finally时，异常在不同的层次抛出 ，在不同的位置抛出，可能会导致不同的finally语句块执行顺序
四、finally语句块一定会执行吗
public class SystemExitAndFinally {
public static void main(String[] args)
{
try{
System.out.println("in main");
throw new Exception("Exception is thrown in main");
//System.exit(0);
}
catch(Exception e)
{
System.out.println(e.getMessage());
System.exit(0);
}
finally
{
System.out.println("in finally");
}
}
}
运行结果：
in main
Exception is thrown in main
分析：在JVM正常运行的情况下，finally块一定会执行。但如果JVM都退出了finally块就无法执行了
五、Java多层嵌套异常处理的基本流程
http://lavasoft.blog.51cto.com/62575/18920/
http://blog.sina.com.cn/s/blog_9d88a5770101gsf4.html
六、成绩判断
源代码：
package 成绩判断;
import javax.swing.JOptionPane;
//<=60 “不及格”、60--69“及格”、70--79 “中”、80--89“良”、90-100“优”
class NumberlimitedExceptiion extends Exception{
NumberlimitedExceptiion(){
JOptionPane.showMessageDialog(null, "所输入的数字超出范围！",
"输出",JOptionPane.INFORMATION_MESSAGE);
}
}
class Shuru{
int score;
public static void prime(int m) throws NumberlimitedExceptiion{
if(m>100||m<0){
NumberlimitedExceptiion limitexcep=new NumberlimitedExceptiion();
throw limitexcep;
}
}
public void input(){
try{
String i=JOptionPane.showInputDialog("请输入一个整数成绩：");
score=Integer.parseInt(i);
}
catch(NumberFormatException e){
JOptionPane.showMessageDialog(null, "输入的不是整数！",
"输出",JOptionPane.INFORMATION_MESSAGE);
input();
}
try{
prime(score);
}
catch(NumberlimitedExceptiion e) {
input();
}
// finally{
//
// }
}
}
public class Juage {
public static void main(String[] args){
Shuru a=new Shuru();
a.input();
if(a.score<60){
JOptionPane.showMessageDialog(null, "此成绩为不及格！",
"输出",JOptionPane.INFORMATION_MESSAGE);
}
else if(a.score<=69){
JOptionPane.showMessageDialog(null, "此成绩为及格！",
"输出",JOptionPane.INFORMATION_MESSAGE);
}
else if(a.score<=79){
JOptionPane.showMessageDialog(null, "此成绩为中等！",
"输出",JOptionPane.INFORMATION_MESSAGE);
}
else if(a.score<=89){
JOptionPane.showMessageDialog(null, "此成绩为良等！",
"输出",JOptionPane.INFORMATION_MESSAGE);
}
else if(a.score<=100){
JOptionPane.showMessageDialog(null, "此成绩为优等！",
"输出",JOptionPane.INFORMATION_MESSAGE);
}
}
}