java - Java7 multiple exception handling -

i have been trying find out answer question did not satisfactory explanation. here background:

java 7 allows catch multiple exceptions in single catch block provided exceptions diffrent hierarchy. eg:

try {     // code  } catch(sqlexception | filenotfoundexception e) {     e.printstacktrace(); } catch(exception e) {     e.printstacktrace(); } 

but if exceptions same hierarchy must use multiple catch blocks like:

try {     // code } catch(filenotfoundexception  e) {     e.printstacktrace(); } catch(ioexception e) {     e.printstacktrace(); } 

but if try write code below compiler complains "the exception filenotfoundexception caught alternative ioexception"

try {     // code } catch(filenotfoundexception | ioexception  e) { // compiler error     e.printstacktrace(); } 

now question is: why compiler reports error in last case, can't figure out filenotfoundexception special case of ioexception? save code duplication when exception handling logic same.

why compiler reports error in last case, can't figure out filenotfoundexception special case of ioexception?

because filenotfoundexception subclass of ioexception. in other words, "filenotfoundexception |" part redundant.

the reason why code below ok...

} catch(filenotfoundexception  e) {     ... } catch(ioexception e) {     ... } 

...is because here ioexception clause matters: if socketexception thrown instance, pass filenotfoundexception part, , caught in ioexception clause.