public abstract class Process extends Object
ProcessBuilder.start() and
Runtime.exec
methods create a native process and return an instance of a
subclass of Process that can be used to control the process
and obtain information about it. 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.
The methods that create processes may not work well for special processes on certain native platforms, such as native windowing processes, daemon processes, Win16/DOS processes on Microsoft Windows, or shell scripts.
By default, the created subprocess does not have its own terminal
or console. All its standard I/O (i.e. stdin, stdout, stderr)
operations will be redirected to the parent process, where they can
be accessed via the streams obtained using the methods
getOutputStream(),
getInputStream(), and
getErrorStream().
The parent process uses these streams to feed input to and get output
from the subprocess. Because some native platforms only provide
limited buffer size for standard input and output streams, failure
to promptly write the input stream or read the output stream of
the subprocess may cause the subprocess to block, or even deadlock.
Where desired,
subprocess I/O can also be redirected
using methods of the ProcessBuilder class.
The subprocess is not killed when there are no more references to
the Process object, but rather the subprocess
continues executing asynchronously.
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.
As of 1.5, ProcessBuilder.start() is the preferred way
to create a Process.
| Constructor and Description |
|---|
Process() |
| Modifier and Type | Method and Description |
|---|---|
abstract void |
destroy()
Kills the subprocess.
|
abstract int |
exitValue()
Returns the exit value for the subprocess.
|
abstract InputStream |
getErrorStream()
Returns the input stream connected to the error output of the
subprocess.
|
abstract InputStream |
getInputStream()
Returns the input stream connected to the normal output of the
subprocess.
|
abstract OutputStream |
getOutputStream()
Returns the output stream connected to the normal input of the
subprocess.
|
abstract int |
waitFor()
Causes the current thread to wait, if necessary, until the
process represented by this
Process object has
terminated. |
public abstract OutputStream getOutputStream()
Process object.
If the standard input of the subprocess has been redirected using
ProcessBuilder.redirectInput
then this method will return a
null output stream.
Implementation note: It is a good idea for the returned output stream to be buffered.
public abstract InputStream getInputStream()
Process object.
If the standard output of the subprocess has been redirected using
ProcessBuilder.redirectOutput
then this method will return a
null input stream.
Otherwise, if the standard error of the subprocess has been
redirected using
ProcessBuilder.redirectErrorStream
then the input stream returned by this method will receive the
merged standard output and the standard error of the subprocess.
Implementation note: It is a good idea for the returned input stream to be buffered.
public abstract InputStream getErrorStream()
Process object.
If the standard error of the subprocess has been redirected using
ProcessBuilder.redirectError or
ProcessBuilder.redirectErrorStream
then this method will return a
null input stream.
Implementation note: It is a good idea for the returned input stream to be buffered.
public abstract int waitFor()
throws InterruptedException
Process object has
terminated. This method returns immediately if the subprocess
has already terminated. If the subprocess has not yet
terminated, the calling thread will be blocked until the
subprocess exits.Process object. By convention, the value
0 indicates normal termination.InterruptedException - if the current thread is
interrupted by another
thread while it is waiting, then the wait is ended and
an InterruptedException is thrown.public abstract int exitValue()
Process object. By convention, the value
0 indicates normal termination.IllegalThreadStateException - if the subprocess represented
by this Process object has not yet terminatedpublic abstract void destroy()
Process object is forcibly terminated.