问题
Possible duplicate: why-is-java-lang-throwable-a-class
Hi! I doesn't understand why Throwable isn't abstract class. I see only one use case for these: in logging systems for figure out call hierarchy. But it can be some static method for this or other class. So, why?)
Thanks.
upd
from java.util.logging.LogRecord
// Get the stack trace.
StackTraceElement stack[] = (new Throwable()).getStackTrace();
Why it can't be Throwable.getStackTrace();
or as in java.lang.Thread
(new Exception()).getStackTrace();
In this way we can avoid throw new Throwable();
upd2 from javadoc
The Throwable class is the superclass of all errors and exceptions in the Java language.
So, as a superclass it should be abstract, imho. Using it for getting stacktrace isn't good case by this definition.
回答1:
I doesn't understand why Throwable isn't abstract class.
The answer is clearly stated here.
Why it can't be Throwable.getStackTrace(); or as in java.lang.Thread
Quite simply, the getStackTrace()
calls the getOurStackTrace()
method which is non-static. If getStackTrace()
was static, so should getOurStackTrace()
. This won't happen as printStackTrace()
method uses the getOurStackTrace()
. This is elaborated in the JavaDoc:
Provides programmatic access to the stack trace information printed by printStackTrace().
Source for java.lang.Throwable:
public StackTraceElement[] getStackTrace() {
return (StackTraceElement[]) getOurStackTrace().clone();
}
Also, if you read the code of getOurStackTrace()
method, you'll see it calls the following method:
private native int getStackTraceDepth();
As far as I know, native cannot be static (I may be wrong).
回答2:
I use it quite often for logging, so I am glad it isn't abstract. There is a method to get the call stack, Thread.currentThread().getStackTrace() but this returns a StackTraceElement[] which isn't very useful for logging.
EDIT:
StackTraceElement[] stes = Thread.currentThread().getStackTrace();
Note: this method also works to get a stack trace of another thread which can be handy.
来源:https://stackoverflow.com/questions/4306214/why-isnt-java-lang-throwable-an-abstract-class