java - Why I cannot instantiate this variable? -

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i have piece of code on jsp file :

// mainhomepage pageapp = new mainhomepage(session);  string pagevalue=request.getparameter("page"); if((pagevalue!=null) && (pagevalue.compareto("1")==0)) {     mainhomepage pageapp = new mainhomepage(session); } else if((pagevalue!=null) && (pagevalue.compareto("2")==0)) {     mainaffittaappartamenti pageapp = new mainaffittaappartamenti(session); } else {     mainhomepage pageapp = new mainhomepage(session); }  pageapp.somemethod();

if don't remove comment on first line said (about pageapp) "cannot find symbol"... why this? if-else instantiate it, in case. wrong? cheers

actually, have should not compile since pageapp not within scope on last line. looks confused between variable declaration , variable assignment. java allows both in same statement, however, may declare variable 1 time within same scope.

if uncomment first declaration still leave others inside if , else statements, compile time errors related duplicate declaration. within if , else statement blocks declaring same variable different types. should find, if possible, abstract type variable shared 2 types instantiating (e.g. mainhomepage , mainaffittaappartamenti) , declare outside if , else blocks , in main method scope.

for example, if mainaffittaappartamenti sub-class mainhomepage can this:

mainhomepage pageapp; // declare here not assign  string pagevalue=request.getparameter("page"); if((pagevalue!=null) && (pagevalue.compareto("1")==0)) {     pageapp = new mainhomepage(session); } else if((pagevalue!=null) && (pagevalue.compareto("2")==0)) {     pageapp = new mainaffittaappartamenti(session); } else {     pageapp = new mainhomepage(session); }  pageapp.somemethod();

notice in inner blocks did not declare variable again (that define it's type). since, given assumption statement, mainaffittaappartamenti sub-class of mainhomepage assignment of pageapp valid still.


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