Java Utililty Methods Zip File Check

return hasCaseInsensitiveSuffix(file, zip_suffix);

return file != null && isZipFile(file.getAbsolutePath());

boolean isZip = true;
byte[] buffer = new byte[ZIP_HEADER.length];
RandomAccessFile raf = null;
try {
    raf = new RandomAccessFile(file, "r");
    raf.readFully(buffer);
    for (int i = 0; i < ZIP_HEADER.length; i++) {
        if (buffer[i] != ZIP_HEADER[i]) {
...

if (file == null || file.isDirectory() || !file.canRead() || file.length() < 4) {
    return false;
try (DataInputStream in = new DataInputStream(new BufferedInputStream(new FileInputStream(file)))) {
    int test = in.readInt();
    return test == 0x504b0304; 
} catch (Exception e) {
    return false;
...

String fileName = file.getPath().toLowerCase();
return (fileName.endsWith(".zip"));

boolean isZipFile = false;
FileInputStream fileInputStream = null;
try {
    fileInputStream = new FileInputStream(file);
    if (fileInputStream.available() > ZIP_SIGNATURE.length) {
        byte[] magic = new byte[ZIP_SIGNATURE.length];
        if (ZIP_SIGNATURE.length == fileInputStream.read(magic, 0, ZIP_SIGNATURE.length)) {
            isZipFile = Arrays.equals(magic, ZIP_SIGNATURE);
...

boolean b = false;
try {
    ZipFile zf = new ZipFile(file);
    zf.close();
    b = true;
} catch (ZipException e) {
    e.printStackTrace();
} catch (IOException e) {
...

if (file != null && file.getName() != null && file.getName().toLowerCase().endsWith(ZIP_FILE.toLowerCase()))
    return true;
else
    return false;

return file.isFile() && file.getName().toLowerCase().endsWith(ZIP_EXTENSION);

DataInputStream in = new DataInputStream(stream);
if (stream.markSupported())
    stream.mark(INT_LENGTH);
int test = in.readInt();
if (stream.markSupported())
    stream.reset();
final int zipVerificationCode = ZIP_VERIFICATION_CODE;
return test == zipVerificationCode;
...