Try to understand Throwable

Question

I saw some sample codes like:
[Base Exception Class]
public class BaseException extends Exception {
public BaseException() {super();}
public BaseException(Throwable exception) {
super();
this.nestedException = exception;
}//end constructor
[Sub Exception]
public class TestException extends BaseException {
public TestException(Throwable exception) {
super(exception);
public TestException() {
super();
[Calling Class]
public Result getData() throws TestException {
try {
connection = ConnectionHelper.getConnection(...);
} catch (SQLException e){
TestException te = new TestException(e);
te.setErrorCode("10000");
throw te;
--What is the purpose of passing the e as Throwable in
new TestException(e);
It seems to me that if use:
TestException te = new TestException();
will also create the object. And
te.setErrorCode("10000");
throw te;
will be just fine. Then why should use the Throwable e to initiate the Object
TestException? Or what is the usage of use the Throwable?
Thanks
Scott

Answer 1

Throwable is the superclass of Exception (or somewhere up there).
The purpose is that you catch an exception in your code, but want to throw a new one, but want to include the original one that started it all.
Generally, I don't normally do that, but it does happen in some places. I've seen this in JSP all the time (what Tomcat does, not what I've done in JSP).