compiler errors - In Java, how can I use a variable initialized inside a try/catch block elsewhere in the program? -

-

i have basic quadratic formula program, i've modified beginning end program if value other double entered. however, because i've done this, can't seem able use value inputted anywhere else in program. here first few lines: 

import java.util.scanner;  public class quadraticformula {   public static void main(string[] args)   {     double a, b, c;      scanner reads = new scanner(system.in);       system.out.println("general equation: \"ax^2 + bx + c\"");     system.out.print("enter value of \"a\": ");      try {        string doublestring = reads.nextline();       = double.parsedouble(doublestring);      }     catch (exception e) {       system.out.println("invalid data type. please enter number");     }

the rest of program asks values of b , c, , carries out quadratic equation, retuning roots of whatever equation entered. however, because value of defined inside try section, compiler tells me hasn't been initialized. how fix this?

edit: want use data inputted user in program (stored doublestring)––but number. immediate problem compiler error, there way use information inputted though it's inside try block? because when tried equate double double doublestring outside block said doublestring didn't exist.

like @elliot frisch said, can initialize a value (0) , take care don't wrong values due failed parsing. in case mean return/exit program error message.

this common pattern.

import java.util.scanner;  public class quadraticformula { public static void main(string[] args) { double = 0, b, c;  scanner reads = new scanner(system.in);   system.out.println("general equation: \"ax^2 + bx + c\""); system.out.print("enter value of \"a\": ");  try {    string doublestring = reads.nextline();   = double.parsedouble(doublestring);  } catch (exception e) {   system.out.println("invalid data type. please enter number");   return; } //do work

Comments

Post a Comment

Popular posts from this blog

Django REST Framework perform_create: You cannot call `.save()` after accessing `serializer.data` -

-
i have following viewset: class artistprofileviewset(viewsets.modelviewset): queryset = artistprofile.objects.all() serializer_class = artistprofileserializer def perform_create(self, serializer): if serializer.is_valid(): serializer.save() with following serializers: class simpleartisttrackserializer(serializers.hyperlinkedmodelserializer): class meta: model = artisttrack fields = (...my fields...) class artistprofileserializer(serializers.hyperlinkedmodelserializer): owners = userserializer(many=true, required=false) tracks = simpleartisttrackserializer(many=true, required=false) class meta: model = artistprofile fields = (...my fields...) i getting following error: assertionerror: cannot call `.save()` after accessing `serializer.data`.if need access data before committing database inspect 'serializer.validated_data' instead. i don't see editing serializer.data object. th...
Read more

Why does Go error when trying to marshal this JSON? -

-
i'm trying rather simple example of trying decode json file structs using golang. however, when attempting error that json: cannot unmarshal object go value of type []main.track which don't understand. here's code in question, , json can found here . package main import ( "encoding/json" "fmt" "net/http" "os" ) // tracks group of track types type tracks struct { tracks []track } // track represents singular track type track struct { name string url string artist artist } // artist represents single artist type artist struct { name string mbid string url string } func main() { url := "http://ws.audioscrobbler.com/2.0/?method=geo.gettoptracks&api_key=c1572082105bd40d247836b5c1819623&format=json&country=netherlands" response, err := http.get(url) if err != nil { fmt.printf("%s\n", err) os.exit(1) } de...
Read more