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	/*
	* Copyright (c) 2014, 2018, Oracle and/or its affiliates. All rights reserved.
	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
	*
	* This code is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License version 2 only, as
	* published by the Free Software Foundation. Oracle designates this
	* particular file as subject to the "Classpath" exception as provided
	* by Oracle in the LICENSE file that accompanied this code.
	*
	* This code is distributed in the hope that it will be useful, but WITHOUT
	* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
	* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
	* version 2 for more details (a copy is included in the LICENSE file that
	* accompanied this code).
	*
	* You should have received a copy of the GNU General Public License version
	* 2 along with this work; if not, write to the Free Software Foundation,
	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
	*
	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*/
	package java.lang;

	import java.time.Duration;
	import java.time.Instant;
	import java.util.Optional;
	import java.util.concurrent.CompletableFuture;
	import java.util.stream.Stream;

	/**
	* ProcessHandle identifies and provides control of native processes. Each
	* individual process can be monitored for liveness, list its children,
	* get information about the process or destroy it.
	* By comparison, {@link java.lang.Process Process} instances were started
	* by the current process and additionally provide access to the process
	* input, output, and error streams.
	* <p>
	* The native process ID is an identification number that the
	* operating system assigns to the process.
	* The range for process id values is dependent on the operating system.
	* For example, an embedded system might use a 16-bit value.
	* Status information about a process is retrieved from the native system
	* and may change asynchronously; processes may be created or terminate
	* spontaneously.
	* The time between when a process terminates and the process id
	* is reused for a new process is unpredictable.
	* Race conditions can exist between checking the status of a process and
	* acting upon it. When using ProcessHandles avoid assumptions
	* about the liveness or identity of the underlying process.
	* <p>
	* Each ProcessHandle identifies and allows control of a process in the native
	* system. ProcessHandles are returned from the factory methods {@link #current()},
	* {@link #of(long)},
	* {@link #children}, {@link #descendants}, {@link #parent()} and
	* {@link #allProcesses()}.
	* <p>
	* The {@link Process} instances created by {@link ProcessBuilder} can be queried
	* for a ProcessHandle that provides information about the Process.
	* ProcessHandle references should not be freely distributed.
	*
	* <p>
	* A {@link java.util.concurrent.CompletableFuture} available from {@link #onExit}
	* can be used to wait for process termination, and possibly trigger dependent
	* actions.
	* <p>
	* The factory methods limit access to ProcessHandles using the
	* SecurityManager checking the {@link RuntimePermission RuntimePermission("manageProcess")}.
	* The ability to control processes is also restricted by the native system,
	* ProcessHandle provides no more access to, or control over, the native process
	* than would be allowed by a native application.
	*
	* @implSpec
	* In the case where ProcessHandles cannot be supported then the factory
	* methods must consistently throw {@link java.lang.UnsupportedOperationException}.
	* The methods of this class throw {@link java.lang.UnsupportedOperationException}
	* if the operating system does not allow access to query or kill a process.
	*
	* <p>
	* The {@code ProcessHandle} static factory methods return instances that are
	* <a href="{@docRoot}/java.base/java/lang/doc-files/ValueBased.html">value-based</a>,
	* immutable and thread-safe.
	* Use of identity-sensitive operations (including reference equality
	* ({@code ==}), identity hash code, or synchronization) on these instances of
	* {@code ProcessHandle} may have unpredictable results and should be avoided.
	* Use {@link #equals(Object) equals} or
	* {@link #compareTo(ProcessHandle) compareTo} methods to compare ProcessHandles.
	*
	* @see Process
	* @since 9
	*/
	public interface ProcessHandle extends Comparable<ProcessHandle> {

	/**
	* Returns the native process ID of the process. The native process ID is an
	* identification number that the operating system assigns to the process.
	* The operating system may reuse the process ID after a process terminates.
	* Use {@link #equals(Object) equals} or
	* {@link #compareTo(ProcessHandle) compareTo} to compare ProcessHandles.
	*
	* @return the native process ID of the process
	* @throws UnsupportedOperationException if the implementation
	* does not support this operation
	*/
	long pid();

	/**
	* Returns an {@code Optional<ProcessHandle>} for an existing native process.
	*
	* @param pid a native process ID
	* @return an {@code Optional<ProcessHandle>} of the PID for the process;
	* the {@code Optional} is empty if the process does not exist
	* @throws SecurityException if a security manager has been installed and
	* it denies RuntimePermission("manageProcess")
	* @throws UnsupportedOperationException if the implementation
	* does not support this operation
	*/
	public static Optional<ProcessHandle> of(long pid) {
	return ProcessHandleImpl.get(pid);
	}

	/**
	* Returns a ProcessHandle for the current process. The ProcessHandle cannot be
	* used to destroy the current process, use {@link System#exit System.exit} instead.
	*
	* @return a ProcessHandle for the current process
	* @throws SecurityException if a security manager has been installed and
	* it denies RuntimePermission("manageProcess")
	* @throws UnsupportedOperationException if the implementation
	* does not support this operation
	*/
	public static ProcessHandle current() {
	return ProcessHandleImpl.current();
	}

	/**
	* Returns an {@code Optional<ProcessHandle>} for the parent process.
	* Note that Processes in a zombie state usually don't have a parent.
	*
	* @return an {@code Optional<ProcessHandle>} of the parent process;
	* the {@code Optional} is empty if the child process does not have a parent
	* or if the parent is not available, possibly due to operating system limitations
	* @throws SecurityException if a security manager has been installed and
	* it denies RuntimePermission("manageProcess")
	*/
	Optional<ProcessHandle> parent();

	/**
	* Returns a snapshot of the current direct children of the process.
	* The {@link #parent} of a direct child process is the process.
	* Typically, a process that is {@link #isAlive not alive} has no children.
	* <p>
	* <em>Note that processes are created and terminate asynchronously.
	* There is no guarantee that a process is {@link #isAlive alive}.
	* </em>
	*
	* @return a sequential Stream of ProcessHandles for processes that are
	* direct children of the process
	* @throws SecurityException if a security manager has been installed and
	* it denies RuntimePermission("manageProcess")
	*/
	Stream<ProcessHandle> children();

	/**
	* Returns a snapshot of the descendants of the process.
	* The descendants of a process are the children of the process
	* plus the descendants of those children, recursively.
	* Typically, a process that is {@link #isAlive not alive} has no children.
	* <p>
	* <em>Note that processes are created and terminate asynchronously.
	* There is no guarantee that a process is {@link #isAlive alive}.
	* </em>
	*
	* @return a sequential Stream of ProcessHandles for processes that
	* are descendants of the process
	* @throws SecurityException if a security manager has been installed and
	* it denies RuntimePermission("manageProcess")
	*/
	Stream<ProcessHandle> descendants();

	/**
	* Returns a snapshot of all processes visible to the current process.
	* <p>
	* <em>Note that processes are created and terminate asynchronously. There
	* is no guarantee that a process in the stream is alive or that no other
	* processes may have been created since the inception of the snapshot.
	* </em>
	*
	* @return a Stream of ProcessHandles for all processes
	* @throws SecurityException if a security manager has been installed and
	* it denies RuntimePermission("manageProcess")
	* @throws UnsupportedOperationException if the implementation
	* does not support this operation
	*/
	static Stream<ProcessHandle> allProcesses() {
	return ProcessHandleImpl.children(0);
	}

	/**
	* Returns a snapshot of information about the process.
	*
	* <p> A {@link ProcessHandle.Info} instance has accessor methods that return
	* information about the process if it is available.
	*
	* @return a snapshot of information about the process, always non-null
	*/
	Info info();

	/**
	* Information snapshot about the process.
	* The attributes of a process vary by operating system and are not available
	* in all implementations. Information about processes is limited
	* by the operating system privileges of the process making the request.
	* The return types are {@code Optional<T>} allowing explicit tests
	* and actions if the value is available.
	* @since 9
	*/
	public interface Info {
	/**
	* Returns the executable pathname of the process.
	*
	* @return an {@code Optional<String>} of the executable pathname
	* of the process
	*/
	public Optional<String> command();

	/**
	* Returns the command line of the process.
	* <p>
	* If {@link #command command()} and {@link #arguments arguments()} return
	* non-empty optionals, this is simply a convenience method which concatenates
	* the values of the two functions separated by spaces. Otherwise it will return a
	* best-effort, platform dependent representation of the command line.
	*
	* @apiNote Note that the returned executable pathname and the
	* arguments may be truncated on some platforms due to system
	* limitations.
	* <p>
	* The executable pathname may contain only the
	* name of the executable without the full path information.
	* It is undecideable whether white space separates different
	* arguments or is part of a single argument.
	*
	* @return an {@code Optional<String>} of the command line
	* of the process
	*/
	public Optional<String> commandLine();

	/**
	* Returns an array of Strings of the arguments of the process.
	*
	* @apiNote On some platforms, native applications are free to change
	* the arguments array after startup and this method may only
	* show the changed values.
	*
	* @return an {@code Optional<String[]>} of the arguments of the process
	*/
	public Optional<String[]> arguments();

	/**
	* Returns the start time of the process.
	*
	* @return an {@code Optional<Instant>} of the start time of the process
	*/
	public Optional<Instant> startInstant();

	/**
	* Returns the total cputime accumulated of the process.
	*
	* @return an {@code Optional<Duration>} for the accumulated total cputime
	*/
	public Optional<Duration> totalCpuDuration();

	/**
	* Return the user of the process.
	*
	* @return an {@code Optional<String>} for the user of the process
	*/
	public Optional<String> user();
	}

	/**
	* Returns a {@code CompletableFuture<ProcessHandle>} for the termination
	* of the process.
	* The {@link java.util.concurrent.CompletableFuture} provides the ability
	* to trigger dependent functions or actions that may be run synchronously
	* or asynchronously upon process termination.
	* When the process has terminated the CompletableFuture is
	* {@link java.util.concurrent.CompletableFuture#complete completed} regardless
	* of the exit status of the process.
	* The {@code onExit} method can be called multiple times to invoke
	* independent actions when the process exits.
	* <p>
	* Calling {@code onExit().get()} waits for the process to terminate and returns
	* the ProcessHandle. The future can be used to check if the process is
	* {@link java.util.concurrent.CompletableFuture#isDone done} or to
	* {@link java.util.concurrent.Future#get() wait} for it to terminate.
	* {@link java.util.concurrent.Future#cancel(boolean) Cancelling}
	* the CompleteableFuture does not affect the Process.
	* @apiNote
	* The process may be observed to have terminated with {@link #isAlive}
	* before the ComputableFuture is completed and dependent actions are invoked.
	*
	* @return a new {@code CompletableFuture<ProcessHandle>} for the ProcessHandle
	*
	* @throws IllegalStateException if the process is the current process
	*/
	CompletableFuture<ProcessHandle> onExit();

	/**
	* Returns {@code true} if the implementation of {@link #destroy}
	* normally terminates the process.
	* Returns {@code false} if the implementation of {@code destroy}
	* forcibly and immediately terminates the process.
	*
	* @return {@code true} if the implementation of {@link #destroy}
	* normally terminates the process;
	* otherwise, {@link #destroy} forcibly terminates the process
	*/
	boolean supportsNormalTermination();

	/**
	* Requests the process to be killed.
	* Whether the process represented by this {@code ProcessHandle} object is
	* {@link #supportsNormalTermination normally terminated} or not is
	* implementation dependent.
	* Forcible process destruction is defined as the immediate termination of the
	* process, whereas normal termination allows the process to shut down cleanly.
	* If the process is not alive, no action is taken.
	* The operating system access controls may prevent the process
	* from being killed.
	* <p>
	* The {@link java.util.concurrent.CompletableFuture} from {@link #onExit} is
	* {@link java.util.concurrent.CompletableFuture#complete completed}
	* when the process has terminated.
	* <p>
	* Note: The process may not terminate immediately.
	* For example, {@code isAlive()} may return true for a brief period
	* after {@code destroy()} is called.
	*
	* @return {@code true} if termination was successfully requested,
	* otherwise {@code false}
	* @throws IllegalStateException if the process is the current process
	*/
	boolean destroy();

	/**
	* Requests the process to be killed forcibly.
	* The process represented by this {@code ProcessHandle} object is
	* forcibly terminated.
	* Forcible process destruction is defined as the immediate termination of the
	* process, whereas normal termination allows the process to shut down cleanly.
	* If the process is not alive, no action is taken.
	* The operating system access controls may prevent the process
	* from being killed.
	* <p>
	* The {@link java.util.concurrent.CompletableFuture} from {@link #onExit} is
	* {@link java.util.concurrent.CompletableFuture#complete completed}
	* when the process has terminated.
	* <p>
	* Note: The process may not terminate immediately.
	* For example, {@code isAlive()} may return true for a brief period
	* after {@code destroyForcibly()} is called.
	*
	* @return {@code true} if termination was successfully requested,
	* otherwise {@code false}
	* @throws IllegalStateException if the process is the current process
	*/
	boolean destroyForcibly();

	/**
	* Tests whether the process represented by this {@code ProcessHandle} is alive.
	* Process termination is implementation and operating system specific.
	* The process is considered alive as long as the PID is valid.
	*
	* @return {@code true} if the process represented by this
	* {@code ProcessHandle} object has not yet terminated
	*/
	boolean isAlive();

	/**
	* Returns a hash code value for this ProcessHandle.
	* The hashcode value follows the general contract for {@link Object#hashCode()}.
	* The value is a function of the {@link #pid pid()} value and
	* may be a function of additional information to uniquely identify the process.
	* If two ProcessHandles are equal according to the {@link #equals(Object) equals}
	* method, then calling the hashCode method on each of the two objects
	* must produce the same integer result.
	*
	* @return a hash code value for this object
	*/
	@Override
	int hashCode();

	/**
	* Returns {@code true} if {@code other} object is non-null, is of the
	* same implementation, and represents the same system process;
	* otherwise it returns {@code false}.
	* @implNote
	* It is implementation specific whether ProcessHandles with the same PID
	* represent the same system process. ProcessHandle implementations
	* should contain additional information to uniquely identify the process.
	* For example, the start time of the process could be used
	* to determine if the PID has been re-used.
	* The implementation of {@code equals} should return {@code true} for two
	* ProcessHandles with the same PID unless there is information to
	* distinguish them.
	*
	* @param other another object
	* @return {@code true} if the {@code other} object is non-null,
	* is of the same implementation class and represents
	* the same system process; otherwise returns {@code false}
	*/
	@Override
	boolean equals(Object other);

	/**
	* Compares this ProcessHandle with the specified ProcessHandle for order.
	* The order is not specified, but is consistent with {@link Object#equals},
	* which returns {@code true} if and only if two instances of ProcessHandle
	* are of the same implementation and represent the same system process.
	* Comparison is only supported among objects of same implementation.
	* If attempt is made to mutually compare two different implementations
	* of {@link ProcessHandle}s, {@link ClassCastException} is thrown.
	*
	* @param other the ProcessHandle to be compared
	* @return a negative integer, zero, or a positive integer as this object
	* is less than, equal to, or greater than the specified object.
	* @throws NullPointerException if the specified object is null
	* @throws ClassCastException if the specified object is not of same class
	* as this object
	*/
	@Override
	int compareTo(ProcessHandle other);

	}

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