public int getDefaultNextBytesSize() {
        return defaultNextBytesSize;
    }
Returns the size of the generated byte array for calls to {@link #nextBytes() nextBytes()}.  Defaults to
{@code 16}, which equals 128 bits, a size commonly used in cryptographic algorithms.

@return the size of the generated byte array for calls to {@link #nextBytes() nextBytes()}.
crypto/core/src/main/java/org/apache/shiro/crypto/SecureRandomNumberGenerator.java