第六讲-异常处理.ppt

第六讲异常处理异常的概念异常的抛出和捕获异常的抛出和捕获示意图三种异常类型Java语言中的部分异常类异常代码的处理try-catch-finally异常匹配顺序//Note:该文件无法通过编译
importjava.io.*;
importjava.util.List;
importjava.util.ArrayList;
publicclassListOfNumbers{
privateList<Integer>list;
privatestaticfinalintSIZE=10;
publicListOfNumbers(){
list=newArrayList<Integer>(SIZE);
for(inti=0;i<SIZE;i++){
list.add(newInteger(i));
}
}
publicvoidwriteList(){
PrintWriterout=newPrintWriter(newFileWriter("OutFile.txt"));
for(inti=0;i<SIZE;i++){
out.println("Valueat:"+i+"="+list.get(i));
}
out.close();}
}
}importjava.io.*;
importjava.util.List;
importjava.util.ArrayList;
publicclassListOfNumbers{
privateList<Integer>list;
privatestaticfinalintSIZE=10;
publicListOfNumbers(){
list=newArrayList<Integer>(SIZE);
for(inti=0;i<SIZE;i++){
list.add(newInteger(i));
}
}
publicvoidwriteList(){
try{
PrintWriterout=newPrintWriter(newFileWriter("OutFile.txt"));
for(inti=0;i<SIZE;i++){
out.println("Valueat:"+i+"="+list.get(i));
}
}
catch(IOExceptionexp){
System.out.println(“CaughtIOException:“+exp.getMessage());
}
finally{
if(out!=null){
System.out.println("ClosingPrintWriter");
out.close();
}
else{
System.out.println("PrintWriternotopen");
}
}
}
}异常声明抛出异常抛出异常语句importjava.util.*;
classExceptionOneextendsException{}
classExceptionTwoextendsException{}
classExceptionThreeextendsExceptionOne{}
classExceptionFourextendsExceptionTwo{}

classBaseClass{
publicvoidf()throwsExceptionOne{thrownewExceptionOne();}
}

publicclassDerivedClassextendsBaseClass{
publicvoidf()throwsExceptionOne,ExceptionTwo{//编译错误，不能抛出父类方法未声明的异常
Randomrand=newRandom();
if(rand.nextInt(15)>5)
thrownewExceptionOne();
else
thrownewExceptionTwo();
}
publicstaticvoidmain(String[]args){
DerivedClassd=newDerivedClass();
try{
d.f();
}
catch(ExceptionOneone){
}
catch(ExceptionTwotwo){
}
}
}importjava.util.*;
classExceptionOneextendsException{}
classExceptionTwoextendsException{}
classExceptionThreeextendsExceptionOne{}
classExceptionFourextendsExceptionTwo{}

classBaseClass{
publicvoidf()throwsExceptionOne{