Java Arraylist reinitialize

Question

So what I'm trying to do is to add an array of strings to my Arraylist BDDvars. The issue I seem to be facing is that after adding 'temp' (which is an array of strings) to the BDDvars list, when I instantly print -- I get values. However, after reinitializing temp, somehow the values that were present in my arraylist are also reset. Would appreciate some help on why this is happening. Thanks!

Code is here:

    List<String[]> BDDvars =new ArrayList<String[]>();

    BDDvars.add(temp);
    System.out.println(BDDvars.get(0)[0]); // this gives value of temp
    for(int n =0;n<11;n++)
      temp[n] = "";
    System.out.println(BDDvars.get(0)[0]); // this gives empty string - why?

You added a _reference_ to the array, not a copy of the array. — Louis Wasserman, Feb 29 '16 at 19:49
Sorry could you see what I've edited and see if you can understand the question better? Thanks — Tushar Sharma, Feb 29 '16 at 19:50
replace your for loop with temp = null; this is simple and you are not messing with reference added to BDDvars. — Srinivasan A, Feb 29 '16 at 19:58

flakes · Accepted Answer · 2016-02-29T19:53:39.500

2

When you add temp to BDDvars you're not creating a new array. Instead both temp and an element in BDDvars are using the same reference.

Make a copy of the array first if you want to modify temp without modifying the value in BDDvars:

String[] tempCopy = new String[temp.length];
System.arraycopy( temp, 0, tempCopy, 0, temp.length);
BDDvars.add(tempCopy);

EDIT

or use clone

BDDvars.add(temp.clone());

edited Feb 29 '16 at 19:53

answered Feb 29 '16 at 19:50

flakes

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You might as well use `.clone()` or `Arrays.copyOf` rather than doing the `System.arraycopy` yourself. – Louis Wasserman Feb 29 '16 at 19:53
@LouisWasserman yup, i over-thought that one haha – flakes Feb 29 '16 at 19:56
1

Excellent. This is what I wanted. Thanks for the prompt response! – Tushar Sharma Feb 29 '16 at 19:57

Java Arraylist reinitialize

1 Answers1