Saving and Retrieving Byte-Level Data
The DataOutputStream Class
The DataOutputStream lets an application write primitive Java data types to an output stream in a portable
way. They can be read back by using a DataInputStream.
public class DataOutputStream extends FilterOutputStream
implements DataOutput
{ // constructor
public DataOutputStream(OutputStream out)
// selected methods
public final void writeBoolean(boolean v) throws IOException
public final void writeByte(int v) throws IOException
public final void writeChar(int v) throws IOException
public final void writeInt(int v) throws IOException
public final void writeDouble(double v) throws IOException
public final void writeBytes(String s) throws IOException
public final void writeUTF(String str) throws IOException
}
The FileOutputStream Class
A FileOutputStream is used to attach an output stream to a file for writing data.
public class FileOutputStream extends OutputStream
{ // selected constructors
public FileOutputStream(String name)
throws FileNotFoundException
public FileOutputStream(String name, boolean append)
throws FileNotFoundException
public FileOutputStream(File file) throws IOException
}
WARNING: If a FileOutputStream uses an existing file name, the existing file is erased without warning.
The FileInputStream Class
This class obtains input bytes from an existing file and returns an InputStream attached to that file.
public class FileInputStream extends InputStream
{ // selected constructors
public FileInputStream(String name) throws FileNotFoundException
public FileInputStream(File file) throws FileNotFoundException
}
The DataInputStream Class
This class lets an application read primitive Java data types from an underlying input stream in a machine-
independent way. The data should have been written by a DataOutputStream.
public class DataInputStream extends FilterInputStream
implements DataInput
{ // constructor
public DataInputStream(InputStream in)
// selected methods
public final int skipBytes(int n) throws IOException
public final boolean readBoolean() throws EOFException, IOException
public final byte readByte() throws EOFException, IOException
public final char readChar() throws EOFException, IOException
public final int readInt() throws EOFException, IOException
public final double readDouble() throws EOFException, IOException
public final String readUTF() throws EOFException, IOException
}
If any of these methods attempt to read past the end of the stream, an EOFException will be generated.
