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");
}
}
}
结构
二、写出程序运行的结果：
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");
}
}
}
结果：
三、请先阅读 EmbedFinally.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");
}
}
}
1.当有多个嵌套的try…catch…finally时，要特别注意finally的执行时机。
2.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、辨析：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");
}
}
}
截图：
没有 System.exit(0);的时候会输出in finally要是有System.exit(0);则会退出系统不执行finally语句。
五、
import javax.swing.JOptionPane;
public class Test{
public static void main(String[] args) {
// TODO 自动生成的方法存根
double n=0.0;
for(int i=0;i<1000000000;i++)
{
String input=JOptionPane.showInputDialog("请输入学生成绩");
try{
n=Double.valueOf(input);
if(n<0)
{
JOptionPane.showMessageDialog(null, "输入不正确");
}
else if(n<60)
{
JOptionPane.showMessageDialog(null,"该学生成绩为不及格");
}
else if(n<70)
{
JOptionPane.showMessageDialog(null,"该学生成绩为及格");
}
else if(n<80)
{
JOptionPane.showMessageDialog(null,"该学生成绩为中等");
}
else if(n<90)
{
JOptionPane.showMessageDialog(null,"该学生成绩为良好");
}
else if(n<=100)
{
JOptionPane.showMessageDialog(null,"该学生成绩为优秀");
}
else if(n>100)
{
JOptionPane.showMessageDialog(null, "输入不正确");
}
}
catch(NumberFormatException e)//NumberFormatException异常
{
JOptionPane.showMessageDialog(null, "输入不正确");
}
}
}
}
结果：
