code: public int[] mergeAllChunks() {
          int[] merged = new int[chunkSize*numChunks];
          int filledChunks = Math.min(numChunks,getFilledChunks()+1);
          for (int i = 0; i < filledChunks ; i++) {
              if (chunks[i]!=null) {
                  System.arraycopy(chunks[i],0,merged,i*chunkSize,chunkSize);
              }
          }
          if (defaultValue!=0) Arrays.fill(merged, size(),merged.length,defaultValue);
          return merged;
      }
docs: turn this chunked array into a regular int-array, mostly for compatibility
  also copying unused space at the end filled with default value