20.15 The Class java.lang.Process

The method exec (§20.16.3) of class Runtime returns a reference to a Process object. The class Process provides methods for performing input from the process, performing output to the process, waiting for the process to complete, checking the exit status of the process, and destroying (killing) the process.

Dropping the last reference to a Process instance, thus allowing the Process object to be reclaimed, does not automatically kill the associated process.

There is no requirement that a process represented by a Process object execute asynchronously or concurrently with respect to the Java process that owns the Process object.

public abstract class Process {
	public abstract OutputStream getOutputStream();
	public abstract InputStream getInputStream();
	public abstract InputStream getErrorStream();
	public abstract int waitFor()

		throws InterruptedException;
	public abstract int exitValue()

		throws IllegalThreadStateException;
	public abstract void destroy();
}

20.15.1 public abstract OutputStream getOutputStream()

This method returns an OutputStream. Output to the stream is piped into the standard input stream of the process represented by this Process object.

Implementation note: It is a good idea for the output stream to be buffered.

20.15.2 public abstract InputStream getInputStream()

This method returns an InputStream. The stream obtains data piped from the standard output stream of the process represented by this Process object.

Implementation note: It is a good idea for the input stream to be buffered.

20.15.3 public abstract InputStream getErrorStream()

This method returns an InputStream. The stream obtains data piped from the error output stream of the process represented by this Process object.

Implementation note: It is a good idea for the input stream to be buffered.

20.15.4 public abstract int waitFor()
throws InterruptedException

This method causes the current thread to wait, if necessary, until the process represented by this Process object has terminated. Then the exit value of the process is returned. By convention, the value 0 indicates normal termination.

If the current thread is interrupted (§20.20.31) by another thread while it is waiting, then the wait is ended and an InterruptedException is thrown.

20.15.5 public abstract int exitValue()
throws IllegalThreadStateException

If the process represented by this Process object has not yet terminated, then an IllegalThreadStateException is thrown. Otherwise, the exit value of the process is returned. By convention, the value 0 indicates normal termination.

20.15.6 public abstract void destroy()

The process represented by this Process object is forcibly terminated.

It was my hint to speak—such was the process.
—William Shakespeare, Othello, Act I, scene iii