The class LongInteger is causing the following error when run:
Exception in thread "main" java.lang.NullPointerException
at LongInteger.breakString(LongInteger.java:38)
at LongInteger.<init>(LongInteger.java:17)
at LongInteger.main(LongInteger.java:149)
Here are some relevant class excerpts:
public class LongInteger extends Object {
private ArrayList<String> storedStrings;
// Constructor
public LongInteger(String s) {
this.setInputString(s);
this.breakString(this.inputString); //Exception @ line 17
}
/**
* the purpose of this method is to break the input string into an
* ArrayList<String> where each String has a length of 9 or less.
*/
private void breakString(String s){
if(s.length()>9){
storedStrings.add(0,s.substring(s.length()-9,s.length()));
this.breakString(s.substring(0,s.length()-9));
} else {
this.storedStrings.add(0,s); //Exception @ line 38
}
}
public static void main(String[] args) {
LongInteger a = new LongInteger("12345"); //Exception @ line 149
}
}
I am at a loss as to what is causing this NullPointerException. Anyone have a suggestion?
You never instantiate storedStrings
. Try changing:
private ArrayList<String> storedStrings;
To:
private ArrayList<String> storedStrings = new ArrayList<String>();
When you have the line:
this.storedStrings.add(0,s);
It is invoking the method add
on an instance of ArrayList<String>
stored in this.storedStrings
. The new
operator is how you get new instances of things.
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