Two collections and a for loop. (Urgent help needed) Checking an object variable against an inputted
- by Elliott
Hi there,
I'm relatively new to java, I'm certain the error is trivial. But can't for the life of me spot it. I have an end of term exam on monday and currently trying to get to grips with past papers!
Anyway heregoes, in another method (ALGO_1) I search over elements of and check the value H_NAME equals a value entered in the main. When I attempt to run the code I get a null pointer exception, also upon trying to print (with System.out.println etc) the H_NAME value after each for loop in the snippet I also get a null statement returned to me.
I am fairly certain that the collection is simply not storing the data gathered up by the Scanner. But then again when I check the collection size with size() it is about the right size. Either way I'm pretty lost and would appreciate the help.
Main questions I guess to ask are:
from the readBackground method is the data.add in the wrong place?
is the snippet simply structured wrongly?
oh and another point when I use System.out.println to check the Background object values name, starttime, increment etc they print out fine.
Thanks in advance.(PS im guessing the formatting is terrible, apologies.)
snippet of code:
for(Hydro hd: hydros){
System.out.println(hd.H_NAME);
for(Background back : backgs){
System.out.println(back.H_NAME);
if(back.H_NAME.equals(hydroName)){ //get error here
public static Collection<Background> readBackground(String url) throws IOException {
URL u = new URL(url);
InputStream is = u.openStream();
InputStreamReader isr = new InputStreamReader(is);
BufferedReader b = new BufferedReader(isr);
String line ="";
Vector<Background> data = new Vector<Background>();
while((line = b.readLine())!= null){
Scanner s = new Scanner(line);
String name = s.next();
double starttime = Double.parseDouble(s.next());
double increment = Double.parseDouble(s.next());
double sum = 0;
double p = 0;
double nterms = 0;
while((s.hasNextDouble())){
p = Double.parseDouble(s.next());
nterms++;
sum += p;
}
double pbmean = sum/nterms;
Background SAMP = new Background(name, starttime, increment, pbmean);
data.add(SAMP);
}
return data;
}
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