array.sort error: java.lang.nullPointerException.
Hi all,
i'm trying to sort an object. My code goes as follows:
public static void sortElemByFitness(){
prepGAGrammar[] gram= new prepGAGrammar[pGA.compoundElem.size()];
try {
BufferedReader in= new BufferedReader(new FileReader(expGAMain.scorefile));
String line;
int temp=0;
while ((line =in.readLine())!= null) {
int ind=line.indexOf(",");
elemNameFromFile.add(line.substring(0, ind));
//System.out.println("temp is:"+temp);
gram[temp]=new prepGAGrammar();
gram[temp].setCompoundElementName(elemNameFromFile.get(temp));
elemFitness.add(Double.parseDouble(line.substring(ind+1)));
gram[temp].setElemFitness(elemFitness.get(temp));
temp++;
}
in.close();
System.out.println("Natural Order");
System.out.println("Index\tElement name\tcomponents\tfitness");
for (int m=0; m<elemNameFromFile.size();m++){
prepGAGrammar g=gram[m];
System.out.print(m+"\t"+g.getCompoundElementName()+ "\t");
for(int n=0; n><pGA.compoundComp.length;n++){
if(pGA.compoundComp[m][n]!=null){
g.setCompoundComponentName(pGA.compoundComp[m][n]);
System.out.print(g.getCompoundComponentName()+" ");
}
}
System.out.print(g.getElemFitness());
System.out.println();
}
Arrays.sort(gram,desc);
System.out.println("Sorted descending by fitness");
System.out.println("Element\t\tfitness");
for (int i=0; i><elemNameFromFile.size(); i++) {
prepGAGrammar g=gram;
ascElem.add(g.getCompoundElementName());
ascFitness.add(g.getElemFitness());
System.out.println(ascElem.get(i)+"\t"+ascFitness.get(i));
}//end for
}catch(IOException e){
e.printStackTrace();
}
}//end method
The output that I got is as follows:
IndexElement namecomponentsfitness
0elemG2-0placename streetname 0.159621785
1elemG2-1business streetname 0.166099364
2elemG2-2placename streetname [number] 0.47627142
3elemG2-3placename business 0.0383857
4elemG2-4streetending anyWord 0.15962179
I try to debug the code from the prepGAGrammar.java file. The compareTo method is as follows:
public int compareTo(Object anotherGrammar) throws ClassCastException {
/*if (!(anotherGrammar instanceof prepGAGrammar))
throw new ClassCastException("A Grammar object expected.");
int anotherGrammarElemFitness= (int)((prepGAGrammar) anotherGrammar ).getElemFitness();
return (int)this.elemFitness- anotherGrammarElemFitness;*/
prepGAGrammar g2= (prepGAGrammar)anotherGrammar; //We receive the object to compare
double f1 = elemFitness; //and we can access to the second object which is compared
double f2 = g2.elemFitness;
System.out.println("-");
System.out.println("f1:"+f1);
System.out.println("f2:"+f2);
//Here we decide which object must come first
if(f1><f2){
return -1;
}else if(f2>f1){
return 1;
}
return 0; //the freqs are equal
}//end method
The output from this is:
-
f1:0.159621785
f2:0.166099364
-
f1:0.159621785
f2:0.47627142
-
f1:0.166099364
f2:0.47627142
-
f1:0.159621785
f2:0.0383857
-
f1:0.0383857
f2:0.15962179
-
f1:0.159621785
f2:0.15962179
-
f1:0.166099364
f2:0.15962179
the errors that i got are:
Exception in thread "main" java.lang.NullPointerException
at prepGAGrammar.compareTo(prepGAGrammar.java:83)
at Descending.compare(Descending.java:9)
at java.util.Arrays.mergeSort(Unknown Source)
at java.util.Arrays.sort(Unknown Source)
at doGA.sortElemByFitness(doGA.java:61)
at expGAMain.main(expGAMain.java:35)
How do I solve this?
help, please..Thank you in advance for your time and concern.
Cheers.
