Nonblocking I/O - Java Network Programming - page 365

Data Conversion
All data in Java ultimately resolves to bytes. Any primitive data type— int , double ,
float , etc.—can be written as bytes. Any sequence of bytes of the right length can be
interpreted as a primitive datum. For example, any sequence of four bytes corresponds
to an int or a float (actually both, depending on how you want to read it). A sequence
of eight bytes corresponds to a long or a double . The ByteBuffer class (and only the
ByteBuffer class) provides relative and absolute put methods that fill a buffer with the
bytes corresponding to an argument of primitive type (except boolean) and relative and
absolute get methods that read the appropriate number of bytes to form a new primitive
datum:
public abstract char getChar ()
public abstract ByteBuffer putChar ( char value )
public abstract char getChar ( int index )
public abstract ByteBuffer putChar ( int index , char value )
public abstract short getShort ()
public abstract ByteBuffer putShort ( short value )
public abstract short getShort ( int index )
public abstract ByteBuffer putShort ( int index , short value )
public abstract int getInt ()
public abstract ByteBuffer putInt ( int value )
public abstract int getInt ( int index )
public abstract ByteBuffer putInt ( int index , int value )
public abstract long getLong ()
public abstract ByteBuffer putLong ( long value )
public abstract long getLong ( int index )
public abstract ByteBuffer putLong ( int index , long value )
public abstract float getFloat ()
public abstract ByteBuffer putFloat ( float value )
public abstract float getFloat ( int index )
public abstract ByteBuffer putFloat ( int index , float value )
public abstract double getDouble ()
public abstract ByteBuffer putDouble ( double value )
public abstract double getDouble ( int index )
public abstract ByteBuffer putDouble ( int index , double value )
In the world of new I/O, these methods do the job performed by DataOutputStream
and DataInputStream in traditional I/O. These methods do have an additional ability
not present in DataOutputStream and DataInputStream . You can choose whether to
interpret the byte sequences as big-endian or little-endian int s, float s, double s, and
so on. By default, all values are read and written as big endian (i.e., most significant byte
first. The two order() methods inspect and set the buffer's byte order using the named
constants in the ByteOrder class. For example, you can change the buffer to little-endian
interpretation like so:
if ( buffer . order (). equals ( ByteOrder . BIG_ENDIAN )) {
buffer . order ( ByteOrder . LITTLE_ENDIAN );
}