DataInputStream

DataInputStream is a Java I/O class that reads primitive Java data types from an underlying input stream in a portable binary format. It extends FilterInputStream and implements the DataInput interface, and is typically used in conjunction with DataOutputStream when a binary, platform-independent data format is required. DataInputStream reads multibyte values in big-endian order, which matches the format produced by DataOutputStream’s writeInt, writeLong, and related methods.

Constructors: DataInputStream(InputStream in). It can wrap any InputStream, and is often combined with BufferedInputStream for efficiency.

The class provides methods to read boolean, byte, unsigned byte, short, unsigned short, char, int, long, float, double, and UTF strings via readUTF. It also offers readFully(byte[] b) and readFully(byte[] b, int off, int len) for bulk reads, and skipBytes(int n) to skip ahead. There is a deprecated readLine method inherited from the DataInput interface; it is not recommended for use.

Exceptions and semantics: Reading beyond end-of-stream throws EOFException; readUTF may throw UTFDataFormatException if the data is not valid modified UTF-8.

Usage considerations: DataInputStream is commonly used to read data written by DataOutputStream. To improve performance, wrap the stream in a BufferedInputStream and ensure that the read order matches the corresponding write order. Closing the stream releases underlying resources. For text data, other classes such as BufferedReader are typically more appropriate.