I am pretty new to java.
I want to have an array of a class whose length may vary during run time
code:
class Num
{
......
......
}
if Num is my class , how will i create new instances. My current code is pretty similar to:
Num n[ ];
int length=0;
.
.
.
n[length++]=new Num();
from this code I'm getting error :
"Uncompilable source code - variable factors might not have been initialized"
You can use an ArrayList for this purpose.
ArrayList<Num> myListOfNum = new ArrayList<Num>();
and then keep adding the objects of Num as and when required.
Num num1 = new Num();
myListOfNum.add(num1);
Num num2 = new Num();
myListOfNum.add(num2);
EDIT:
And to access you can use the get() method along with the specific index.
Num tempNum = myListOfNum.get(indexGoesHere);
List supports both serial access (using iterator or listIterator) as well as random access (using get, set, add, etc.)You need to first create the array itself, before you are trying to set the elements in it.
Num[] n = new Num[SIZE];
Note that Num n[]; is just declaring a variable of type Num[] with the identifier n.
Note however, that in java - arrays are of fixed lengths. If you are looking for a variable length array, an array is probably not what you need. @KazekageGaara suggested an alternative - for this purpose.
Use the Java Collection
List will be good if sequence is more important.
Set if uniqueness is important
Map when key-value pair is important
List<MyClass> arrList = new ArrayList<MyClass>();
arrList.add(mobj1);
arrList.add(mobj2);
arrList.add(mobj3);
for(MyClass m : arrList){
// m is the Values of arrList stored in
}
The simple way to do this is by using ArrayList
ArrayList<Num> numList = new ArrayList<>();
// Add elements to the ArrayList
numList.add(new Num());
numList.add(new Num());
factorsdeclared but not initialized?