java07课堂作业

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);

}

}

}