Java Utililty Methods RandomAccessFile Read

byte[] buf = new byte[1024 * 1024]; 
main.seek(main.length());
extra.seek(0);
while (true) {
    int count = extra.read(buf);
    if (count == -1)
        break;
    main.write(buf, 0, count);
...

return load(new File(f));

if (m <= 0 && n <= 0)
    return null;
RandomAccessFile file = new RandomAccessFile(fn, "r");
long l = file.length();
if (l < 0) {
    file.close();
    return null;
l /= dt_size[type];
if (m <= 0)
    m = (int) (l / n);
else if (n <= 0)
    n = (int) (l / m);
if (m <= 0 || n <= 0) {
    file.close();
    return null;
double[][] x = new double[m][n];
switch (type) {
case DT_BYTE: 
    for (int j = 0; j < n; j++)
        for (int i = 0; i < m; i++)
            x[i][j] = (double) (0xff & (int) file.readByte());
    break;
case DT_SHORT:
    for (int j = 0; j < n; j++)
        for (int i = 0; i < m; i++)
            x[i][j] = (double) file.readShort();
    break;
case DT_INT:
    for (int j = 0; j < n; j++)
        for (int i = 0; i < m; i++)
            x[i][j] = (double) file.readInt();
    break;
case DT_FLOAT:
    for (int j = 0; j < n; j++)
        for (int i = 0; i < m; i++)
            x[i][j] = (double) file.readFloat();
    break;
case DT_DOUBLE:
    for (int j = 0; j < n; j++)
        for (int i = 0; i < m; i++)
            x[i][j] = file.readDouble();
    break;
default:
    file.close();
    throw new IllegalArgumentException("Illegal data type");
file.close();
return x;

int bytes_per_record = 8; 
CheckFile(filename);
File map_file = new File(filename);
long file_size = map_file.length();
if (file_size % bytes_per_record != 0)
    throw new IllegalArgumentException(filename + " is not a d-space map.");
long n_ids = file_size / bytes_per_record;
byte[] buffer = new byte[(int) file_size];
...

try {
    RandomAccessFile r_file = new RandomAccessFile(filename, "r");
    long num_bytes = r_file.length();
    if (num_bytes >= 4l * (long) (Integer.MAX_VALUE))
        throw new IllegalArgumentException("File has more than " + Integer.MAX_VALUE
                + " float values and can't be loaded into an array");
    int num_floats = (int) (num_bytes / 4);
    float[] list = new float[num_floats];
...

int bytes_per_record = n_ghosts * 12; 
CheckFile(filename);
File ghost_file = new File(filename);
long file_size = ghost_file.length();
if (file_size % bytes_per_record != 0)
    throw new IllegalArgumentException(filename + " is not a ghost map.");
if (file_size < bytes_per_record * n_ghosts)
    throw new IllegalArgumentException(filename + " only has records for " + file_size / bytes_per_record
...

HashMap<String, Object> arraydesc = new HashMap<>();
arraydesc.put("arrstart", read_long(raf));
int arrStart = (int) arraydesc.get("arrstart");
switch (arrStart) {
case 8:
    skip_bytes(raf, 4);
    arraydesc.put("nbytes", read_long(raf));
    arraydesc.put("nelements", read_long(raf));
...

byte[] data = new byte[4];
int intData = -1;
try {
    raf.read(data);
    intData = ByteBuffer.wrap(data).getInt();
} catch (IOException e) {
return intData;
...

byte[] data = new byte[4];
raf.read(data);
ByteBuffer bb = ByteBuffer.allocate(data.length);
bb.put(data);
return bb.getInt(0);

int length = read_long(raf);
String result;
if (length > 0) {
    byte[] data = new byte[length];
    raf.read(data);
    align_32(raf);
    result = new String(data, StandardCharsets.UTF_8);
} else {
...