console should allow to change dir using exec(.,.,dir)

Typing "cd something" should change the working directory accordingly. Java allows this. If some JDK don't, a check could be made (if... then... else...)

Here's from JDK1.3 documentation...

public Process exec(String[] cmdarray,
String[] envp,
File dir)
throws IOException

Executes the specified command and arguments in a separate process with the specified environment and working directory.

If there is a security manager, its checkExec method is called with the first component of the array cmdarray as its argument.
This may result in a security exception.

Given an array of strings cmdarray, representing the tokens of a command line, and an array of strings envp, representing
"environment" variable settings, this method creates a new process in which to execute the specified command.

If envp is null, the subprocess inherits the environment settings of the current process.

The working directory of the new subprocess is specified by dir. If dir is null, the subprocess inherits the current working
directory of the current process.
Parameters:
cmdarray - array containing the command to call and its arguments.
envp - array of strings, each element of which has environment variable settings in format name=value.
dir - the working directory of the subprocess, or null if the subprocess should inherit the working directory of the
current process.
Returns:
a Process object for managing the subprocess.
Throws:
SecurityException - if a security manager exists and its checkExec method doesn't allow creation of a subprocess.
NullPointerException - if cmdarray is null.
IndexOutOfBoundsException - if cmdarray is an empty array (has length 0).
IOException - if an I/O error occurs.
See Also:
Process, SecurityException, SecurityManager.checkExec(java.lang.String)