cloning an array of objects in java trowing pointing to null exception

Question

while trying to clone an array of objects, i am getting an error when the array is not completely full. if the list is full, everything works just fine!

this is my code:

    public Object clone() throws CloneNotSupportedException  {
        EmployeeList listBackup = new EmployeeList();
        for (Employee employeeObj : listEmployee){
             listBackup.add( (Employee) employeeObj.clone() );  
        }
        return listBackup;
    }

is there any other way to rewrite this code, when the element in the array is null?

It is NOT an "array" of objects. It is a "list" of objects. If the was really a Java array, you could just use the built-in array clone() method and it would cope with null just fine. — Stephen C
– Stephen C, Commented Feb 16, 2013 at 3:06

A--C · Accepted Answer · 2013-02-16 03:22:57Z

1

Do a null check.

 for (Employee employeeObj : listEmployee){
   if (employeeObj != null)
     listBackup.add( (Employee) employeeObj.clone());  
 }

Or if you want to break the loop as soon as a null value is found:

for (Employee employeeObj : listEmployee){
  if (employeeObj == null)
    break;
  listBackup.add( (Employee) employeeObj.clone());  
}

Or simply return as soon as you come across a null reference

for (Employee employeeObj : listEmployee){
      if (employeeObj == null)
        return listBackup;
      listBackup.add( (Employee) employeeObj.clone());  
    }

Of course, if you can, avoid having your array/list contain null values to begin with, and as @StephenC pointed out, if this is an actual array, you can clone it. However, this depends on the assignment specifications, other code implementation and what your professor allows you to do.

edited Feb 16, 2013 at 3:22

answered Feb 16, 2013 at 2:33

A--C

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5 Comments

Pisike007 Over a year ago

is there any way to put this condition inside the loop? so when its null just breaks the loop and return the list? this works just perfectly find.. but i suppose if the list is too long the loop is not finish until the last element of the array no?

A--C Over a year ago

@PatriciaQuintanilla simply break; once you come across a null reference. Edited the answer.

Pisike007 Over a year ago

i wish i could, this is for a homework, and i have absolute forbidden the use of break in side a loop. my professor rule is never use it if is not in a switch statement!

A--C Over a year ago

So he allows you to use an enhanced for loop, to use clone(), but not break inside a for? There are more "creative" ways to break without using break. I edited again to return listBackup outright.

A--C Over a year ago

No problem, and yes, just return. Of course, if your professor would only allow you to break, you wouldn't have two of the same return statements. To each their own I guess.

phcoding · Accepted Answer · 2013-02-16 02:59:07Z

0

Im not sure that you understood A--C's answer, s/he gave you two seperate solutions, one with a break clause and one without. The 1st solution s/he gave answers your question exactly :)

answered Feb 16, 2013 at 2:59

phcoding

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2 Comments

A--C Over a year ago

He* :-) and the first solution will iterate over the whole array, which is bad to an extent. Returning is the "nicest" option without a break.

Pisike007 Over a year ago

yes, i think i will go with that one.. hope he doesnt take points out because of that! thanks a lot.. i been going crazy with this problem!

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