Text and Binary Files
Binary files
Read from a binary file
Common methods of the DataInput interface
| Method | Throws | Description |
|---|---|---|
| readBoolean() | EOFException | Reads 1 byte and returns a boolean value. |
| readInt() | EOFException | Reads 4 bytes and returns an int value. |
| readDouble() | EOFException | Reads 8 bytes and returns a double value. |
| readChar() | EOFException | Reads 2 bytes and returns a char value. |
| readUTF() | EOFException | Reads and returns the string encoded with UTF. |
| skipBytes(int) | EOFException | Tries to skip the specified number of bytes, and returns an int value for the actual number skipped. |
Common methods of the DataInputStream class
| Method | Throws | Description |
|---|---|---|
| available() | IOException | Returns the number of bytes remaining in the file. |
| close() | IOException | Closes the stream. |
CAUTION: You have to read the data in the same order and same format in which they are stored. For example, since names are written in UTF-8 using writeUTF, you must read names using readUTF.
TIP: If you keep reading data at the end of a stream, an EOFException would occur. So how do you check the end of a file? You can use input.available() to check it.
input.available() == 0 indicates that it is the end of a file.
Code that reads a Product object from a binary file
// read product data from a file String code = in.readUTF(); String description = in.readUTF(); double price = in.readDouble(); // create the Product object from its data Product p = new Product(code, description, price); // close the input stream in.close();