What is the "general contract" of a method

I'm looking at the the java docs for DataInputStream here: http://docs.oracle.com/javase/7/docs/api/java/io/DataInputStream.html

I'm looking to see what its methods do so I look at the descriptions of readBoolean() , readByte(), readChar()etc.

The descriptions are all something along the lines of:

See the general contract of the readBoolean method of DataInput.

And in the extended explanation.

public final boolean readBoolean()
                          throws IOException
See the general contract of the readBoolean method of DataInput.
Bytes for this operation are read from the contained input stream.

Specified by:
readBoolean in interface DataInput

Returns:
the boolean value read.

Throws:
EOFException - if this input stream has reached the end.
IOException - the stream has been closed and the contained input stream does not support reading after close, or another I/O error occurs.

See Also:
FilterInputStream.in

Where can I "see" the general contracts of these methods and what is a general contract of a method?