Didn't you check the javadoc? It tells you exactly what to put there.
Or one of the thousand examples you can find through google...
Information collects on the internet. You'd think that after 15 years some questions would stop to be asked because you can so incredibly easily find the answer. But nope.
need to use Runtime.exec(String command, String env) in that i want to specify , System.setProperty("user.dir",value)
how can i use this in string array of env ,
That isn't going to work.
'System.setProperty' is Java - it has NO meaning for the OS. And even if you set that 'name=value' pair it will only be set in the environment for the 'command' that you use 'exec' to execute; it will not affect your current Java code.
What is it you are really tring to do.