- java.lang.Object
-
- java.lang.Process
-
public abstract class Process extends Object
TheProcessBuilder.start()
andRuntime.exec
methods create a native process and return an instance of a subclass ofProcess
that can be used to control the process and obtain information about it. The classProcess
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()
, andgetErrorStream()
. 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 theProcess
object.As of 1.5,
ProcessBuilder.start()
is the preferred way to create aProcess
.- Since:
- JDK1.0
-
-
Constructor Summary
Constructors Constructor and Description Process()
-
Method Summary
Methods 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 thisProcess
object has terminated.
-
-
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Method Detail
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getOutputStream
public abstract OutputStream getOutputStream()
Returns the output stream connected to the normal input of the subprocess. Output to the stream is piped into the standard input of the process represented by thisProcess
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.
- Returns:
- the output stream connected to the normal input of the subprocess
-
getInputStream
public abstract InputStream getInputStream()
Returns the input stream connected to the normal output of the subprocess. The stream obtains data piped from the standard output of the process represented by thisProcess
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.
- Returns:
- the input stream connected to the normal output of the subprocess
-
getErrorStream
public abstract InputStream getErrorStream()
Returns the input stream connected to the error output of the subprocess. The stream obtains data piped from the error output of the process represented by thisProcess
object.If the standard error of the subprocess has been redirected using
ProcessBuilder.redirectError
orProcessBuilder.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.
- Returns:
- the input stream connected to the error output of the subprocess
-
waitFor
public abstract int waitFor() throws InterruptedException
Causes the current thread to wait, if necessary, until the process represented by thisProcess
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.- Returns:
- the exit value of the subprocess represented by this
Process
object. By convention, the value0
indicates normal termination. - Throws:
InterruptedException
- if the current thread is interrupted by another thread while it is waiting, then the wait is ended and anInterruptedException
is thrown.
-
exitValue
public abstract int exitValue()
Returns the exit value for the subprocess.- Returns:
- the exit value of the subprocess represented by this
Process
object. By convention, the value0
indicates normal termination. - Throws:
IllegalThreadStateException
- if the subprocess represented by thisProcess
object has not yet terminated
-
destroy
public abstract void destroy()
Kills the subprocess. The subprocess represented by thisProcess
object is forcibly terminated.
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