java automatically doubling array size

Question

trying to initialize my array at 1 and have it double every time it's input fills up. this is what i have right now

int max = 1;
 PhoneRecord[] records = new PhoneRecord[max];
      int numRecords = 0;
      int size = Integer.parseInt(length.records[numRecords]);
 if (size >= max) {
   size = 2*size;
 }

but it's clearly full of fail. any suggestions or guidance would be great, thanks.

ArrayList is similar implementation. use that. – Nishant Oct 15 '12 at 16:59 — Nishant, Oct 15 '12 at 16:59

score 1 · Answer 1 · answered Oct 15 '12 at 16:59

1

Why not use an ArrayList ? It'll exhibit very similar characteristics automatically.

From the private grow() method:

int newCapacity = oldCapacity + (oldCapacity >> 1);

You can't override the growth behaviour, but unless you really require a doubling due to your app characteristics, I'm sure it'll be sufficient.

answered Oct 15 '12 at 16:59

Brian Agnew

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:) honestly this is a comment. – Nishant Oct 15 '12 at 16:59
1

If you give me time, I was adding additional info/evidence/links etc :-) – Brian Agnew Oct 15 '12 at 17:02
i would use an array list, but it's for a class i'm in and we have to use what he's told us to use ><. that's why it's so frustrating. – Evan Lemmons Oct 15 '12 at 17:04

nneonneo · Accepted Answer · 2012-10-15T17:18:34.900

1

OK, you should use an ArrayList, but several other folks already told you that.

If you still want to use an array, here's how you'd resize it:

int max = 1;
PhoneRecord[] records = new PhoneRecord[max];
int numRecords = 0;

void addRecord(PhoneRecord rec) {
    records[numRecords++] = rec;
    if(numRecords == max) {
        /* out of space, double the array size */
        max *= 2;
        records = Arrays.copyOf(records, max);
    }
}

edited Oct 15 '12 at 17:18

answered Oct 15 '12 at 17:11

nneonneo

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getting this error talking about the "void addRecord(PhoneRecord rec) { – Evan Lemmons Oct 16 '12 at 12:52
File: D:\School\CSC 2310\Book Progs\PhoneDirectory.java [line: 31] Error: Syntax error on token(s), misplaced construct(s) File: D:\School\CSC 2310\Book Progs\PhoneDirectory.java [line: 31] Error: Syntax error, insert ";" to complete Statement getting this error talking about the void addRecord(PhoneRecord rec) line – Evan Lemmons Oct 16 '12 at 12:53

score 1 · Answer 3 · answered Oct 15 '12 at 17:16

1

Size is only multiplying the size number, not double the array size. Try:

            records = Arrays.copyOf(records, records.length*2);

answered Oct 15 '12 at 17:16

PbxMan

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java automatically doubling array size

3 Answers3