adding in a ArrayList by casting an Object, from table of Objects, into double -

why cast (double) doesn't work ? nead add doubles arraylist.

import java.util.arraylist; import java.util.listiterator;   public class vecteur extends arraylist implements cloneable{     int n;      public vecteur(int n, object ... v){         this.n=n;         if(v.length>=n)             for(int i=0; i<n; i++)                 add((double)v[i]);         else{             for(int i=0; i<v.length; i++){                 if(i<n) add((double)v[i]);                 add(0);             }         }     } } 

is there particular reason not using generics?

you try making class header this:

public class vecteur<t> extends arraylist<t> implements cloneable {... 

then constructor:

public vecteur(int n, t... v) {... 

which apply class generic type constructor. in manner, can remove cast code long instantiate container syntax this:

vecteur<double> v = new vecteur<double>(); 

if need information on generics, check out wikipedia page:

generics in java - wikipedia

edit/update:
error in comment expected see. can use java.lang.double wrapper class exception handling disallow trying add objects aren't castable double:

try { add(double.valueof(v[i].tostring()).doublevalue()); } catch(numberformatexception nfex) { nfex.printstacktrace(); } 

if don't use type of handling you'll classcastexceptions.