Question

I have an ArrayList of my own class Case. The class case provides the method getCaseNumber() I want to add all of the cases casenumber to a String[] caseNumber. I’ve tried this

public String[] getCaseNumberToTempList(ArrayList<Case> caseList) {

    String[] objectCaseNumber = null; 

    for(int i = 0; i < caseList.size(); i++) {
        objectCaseNumber[i] = caseList.get(i).getCaseNumber();  
    }

    return objectCaseNumber;

}

But my compiler complaints about that the objectCaseNumber is null at the point insid the for-loop. How can I manage to complete this?

Answer 1

Well, you need to create an array to start with, and initialize the variable with a reference to the array. (See the Java tutorial for arrays for more information.) For example:

String[] objectCaseNumber = new String[caseList.size()]; 

Alternatively, build a List<String> (e.g. using ArrayList) instead. That’s more flexible – in this case it’s simple as you know the size up front, but in other cases being able to just add to a list makes life a lot simpler.