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三． 以finally进行清理
1. 如果某段代码不管是否发生异常都要执行，那可把它改入finally块中。
import java.sql.SQLException;
class TestException{
public static void tSql() throws SQLException {
System.out.println("Originating the exception in tSql()");
throw new SQLException("throw in tSql");
}
public void f() throws SQLException{
try{
tSql();
}
catch(SQLException ex){
System.out.println("catch SQLException in f()");
throw ex;//（1）
}
finally{
System.out.println("finally in f()");
}
}
}
public class Test{
public static void main(String[] args){
TestException te = new TestException();
try{
te.f();
}
catch(SQLException ex){
System.out.println("catch te.f() SQLException in main");
}
catch(Exception ex){
System.out.println("catch te.f() Exception in main");
}
}
}
运行结果为：
Originating the exception in tSql()
catch SQLException in f()
finally in f()
catch te.f() SQLException in main
虽然在代码（1）处重新抛出异常，但finally块中的代码仍然会被执行。
2. finally造成的异常遗失
如果在finally中执行的代码又产生异常，那么在上一层调用中所捕捉到的异常的起始抛出点会是finally所在的函数。
import java.sql.SQLException;
class TestException{
public static void tSql1() throws SQLException {
System.out.println("Originating the exception in tSql()");
throw new SQLException("throw in tSql1");
}
public static void tSql2() throws SQLException {
System.out.println("Originating the exception in tSql()");
throw new SQLException("throw in tSql2");
}
public void f() throws SQLException{
try{
tSql1();
}
catch(SQLException ex){
System.out.println("catch SQLException in f()");
throw ex;//（2）
}
finally{
System.out.println("finally in f()");
//tSql2();（1）
}
}
}
public class Test{
public static void main(String[] args){
TestException te = new TestException();
try{
te.f();
}
catch(SQLException ex){
System.out.println("catch te.f() SQLException in main");
System.out.println("getMessage：" + ex.getMessage());
System.out.println("printStackTrace：");
ex.printStackTrace();
}
}
}
运行结果为：
Originating the exception in tSql()
catch SQLException in f()
finally in f()
catch te.f() SQLException in main
getMessage：throw in tSql1
printStackTrace：
java.sql.SQLException: throw in tSql1
void TestException.tSql1()
Test.java:5
void TestException.f()
Test.java:13
void Test.main(java.lang.String[])
Test.java:29
从结果可以看出，在main()中能正确打印出所捕捉到的异常的起始抛出点。但如果去掉代码（1）的注释，结果将变为：
Originating the exception in tSql()
catch SQLException in f()
finally in f()
Originating the exception in tSql()
catch te.f() SQLException in main
getMessage：throw in tSql2
printStackTrace：
java.sql.SQLException: throw in tSql2
void TestException.tSql2()
Test.java:9
void TestException.f()
Test.java:21
void Test.main(java.lang.String[])
Test.java:29
从结果可以看出，在main()中捕捉到的异常是finally中产生的异常，代码（2）中抛出的异常丢失了。
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