How to execute linux command in android programmatically?

As in android(through android sdk/tools folder) from command line we can execute linux shell command to access mnt folder/data folder likewise. (e.g cd data ls) now that command i want to execute from programmatically in android so how could it be possible?

Process p = Runtime.getRuntime().exec("cd data");

but it is giving me exception

java.io.IOException: Error running exec(). Command: [cd, data] Working Directory:  null Environment: null