runtime.java

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   * <code>false</code>. There is a security check, <code>checkExit(0)</code>.
   *
   * @param finalizeOnExit whether to finalize all Objects on exit
   * @throws SecurityException if permission is denied
   * @see #exit(int)
   * @see #gc()
   * @since 1.1
   * @deprecated never rely on finalizers to do a clean, thread-safe,
   *             mop-up from your code
   */
  public static void runFinalizersOnExit(boolean finalizeOnExit)
  {
    SecurityManager sm = securityManager; // Be thread-safe!
    if (sm != null)
      sm.checkExit(0);
    current.finalizeOnExit = finalizeOnExit;
  }

  /**
   * Create a new subprocess with the specified command line. Calls
   * <code>exec(cmdline, null, null)<code>. A security check is performed,
   * <code>checkExec</code>.
   *
   * @param cmdline the command to call
   * @return the Process object
   * @throws SecurityException if permission is denied
   * @throws IOException if an I/O error occurs
   * @throws NullPointerException if cmdline is null
   * @throws IndexOutOfBoundsException if cmdline is ""
   */
  public Process exec(String cmdline) throws IOException
  {
    return exec(cmdline, null, null);
  }

  /**
   * Create a new subprocess with the specified command line and environment.
   * If the environment is null, the process inherits the environment of
   * this process. Calls <code>exec(cmdline, env, null)</code>. A security
   * check is performed, <code>checkExec</code>.
   *
   * @param cmdline the command to call
   * @param env the environment to use, in the format name=value
   * @return the Process object
   * @throws SecurityException if permission is denied
   * @throws IOException if an I/O error occurs
   * @throws NullPointerException if cmdline is null, or env has null entries
   * @throws IndexOutOfBoundsException if cmdline is ""
   */
  public Process exec(String cmdline, String[] env) throws IOException
  {
    return exec(cmdline, env, null);
  }

  /**
   * Create a new subprocess with the specified command line, environment, and
   * working directory. If the environment is null, the process inherits the
   * environment of this process. If the directory is null, the process uses
   * the current working directory. This splits cmdline into an array, using
   * the default StringTokenizer, then calls
   * <code>exec(cmdArray, env, dir)</code>. A security check is performed,
   * <code>checkExec</code>.
   *
   * @param cmdline the command to call
   * @param env the environment to use, in the format name=value
   * @param dir the working directory to use
   * @return the Process object
   * @throws SecurityException if permission is denied
   * @throws IOException if an I/O error occurs
   * @throws NullPointerException if cmdline is null, or env has null entries
   * @throws IndexOutOfBoundsException if cmdline is ""
   * @since 1.3
   */
  public Process exec(String cmdline, String[] env, File dir)
    throws IOException
  {
    StringTokenizer t = new StringTokenizer(cmdline);
    String[] cmd = new String[t.countTokens()];
    for (int i = 0; i < cmd.length; i++)
      cmd[i] = t.nextToken();
    return exec(cmd, env, dir);
  }

  /**
   * Create a new subprocess with the specified command line, already
   * tokenized. Calls <code>exec(cmd, null, null)</code>. A security check
   * is performed, <code>checkExec</code>.
   *
   * @param cmd the command to call
   * @return the Process object
   * @throws SecurityException if permission is denied
   * @throws IOException if an I/O error occurs
   * @throws NullPointerException if cmd is null, or has null entries
   * @throws IndexOutOfBoundsException if cmd is length 0
   */
  public Process exec(String[] cmd) throws IOException
  {
    return exec(cmd, null, null);
  }

  /**
   * Create a new subprocess with the specified command line, already
   * tokenized, and specified environment. If the environment is null, the
   * process inherits the environment of this process. Calls
   * <code>exec(cmd, env, null)</code>. A security check is performed,
   * <code>checkExec</code>.
   *
   * @param cmd the command to call
   * @param env the environment to use, in the format name=value
   * @return the Process object
   * @throws SecurityException if permission is denied
   * @throws IOException if an I/O error occurs
   * @throws NullPointerException if cmd is null, or cmd or env has null
   *         entries
   * @throws IndexOutOfBoundsException if cmd is length 0
   */
  public Process exec(String[] cmd, String[] env) throws IOException
  {
    return exec(cmd, env, null);
  }

  /**
   * Create a new subprocess with the specified command line, already
   * tokenized, and the specified environment and working directory. If the
   * environment is null, the process inherits the environment of this
   * process. If the directory is null, the process uses the current working
   * directory. A security check is performed, <code>checkExec</code>.
   *
   * @param cmd the command to call
   * @param env the environment to use, in the format name=value
   * @param dir the working directory to use
   * @return the Process object
   * @throws SecurityException if permission is denied
   * @throws IOException if an I/O error occurs
   * @throws NullPointerException if cmd is null, or cmd or env has null
   *         entries
   * @throws IndexOutOfBoundsException if cmd is length 0
   * @since 1.3
   */
  public Process exec(String[] cmd, String[] env, File dir)
    throws IOException
  {
    SecurityManager sm = securityManager; // Be thread-safe!
    if (sm != null)
      sm.checkExec(cmd[0]);
    return execInternal(cmd, env, dir);
  }

  /**
   * Returns the number of available processors currently available to the
   * virtual machine. This number may change over time; so a multi-processor
   * program want to poll this to determine maximal resource usage.
   *
   * @return the number of processors available, at least 1
   */
  public native int availableProcessors();

  /**
   * Find out how much memory is still free for allocating Objects on the heap.
   *
   * @return the number of bytes of free memory for more Objects
   */
  public native long freeMemory();

  /**
   * Find out how much memory total is available on the heap for allocating
   * Objects.
   *
   * @return the total number of bytes of memory for Objects
   */
  public native long totalMemory();

  /**
   * Returns the maximum amount of memory the virtual machine can attempt to
   * use. This may be <code>Long.MAX_VALUE</code> if there is no inherent
   * limit (or if you really do have a 8 exabyte memory!).
   *
   * @return the maximum number of bytes the virtual machine will attempt
   *         to allocate
   */
  public native long maxMemory();

  /**
   * Run the garbage collector. This method is more of a suggestion than
   * anything. All this method guarantees is that the garbage collector will
   * have "done its best" by the time it returns. Notice that garbage
   * collection takes place even without calling this method.
   */
  public native void gc();

  /**
   * Run finalization on all Objects that are waiting to be finalized. Again,
   * a suggestion, though a stronger one than {@link #gc()}. This calls the
   * <code>finalize</code> method of all objects waiting to be collected.
   *
   * @see #finalize()
   */
  public native void runFinalization();

  /**
   * Tell the VM to trace every bytecode instruction that executes (print out
   * a trace of it).  No guarantees are made as to where it will be printed,
   * and the VM is allowed to ignore this request.
   *
   * @param on whether to turn instruction tracing on
   */
  public native void traceInstructions(boolean on);

  /**
   * Tell the VM to trace every method call that executes (print out a trace
   * of it).  No guarantees are made as to where it will be printed, and the
   * VM is allowed to ignore this request.
   *
   * @param on whether to turn method tracing on
   */
  public native void traceMethodCalls(boolean on);

  /**
   * Load a native library using the system-dependent filename. This is similar
   * to loadLibrary, except the only name mangling done is inserting "_g"
   * before the final ".so" if the VM was invoked by the name "java_g". There
   * may be a security check, of <code>checkLink</code>.
   *
   * @param filename the file to load
   * @throws SecurityException if permission is denied
   * @throws UnsatisfiedLinkError if the library is not found
   */
  public void load(String filename)
  {
    SecurityManager sm = securityManager; // Be thread-safe!
    if (sm != null)
      sm.checkLink(filename);
    _load(filename, false);
  }

  /**
   * Load a native library using a system-independent "short name" for the
   * library.  It will be transformed to a correct filename in a
   * system-dependent manner (for example, in Windows, "mylib" will be turned
   * into "mylib.dll").  This is done as follows: if the context that called
   * load has a ClassLoader cl, then <code>cl.findLibrary(libpath)</code> is
   * used to convert the name. If that result was null, or there was no class
   * loader, this searches each directory of the system property
   * <code>java.library.path</code> for a file named
   * <code>System.mapLibraryName(libname)</code>. There may be a security
   * check, of <code>checkLink</code>.
   *
   * @param filename the file to load
   * @throws SecurityException if permission is denied
   * @throws UnsatisfiedLinkError if the library is not found
   * @see System#mapLibraryName(String)
   * @see ClassLoader#findLibrary(String)
   */
  public void loadLibrary(String libname)
  {
    // This is different from the Classpath implementation, but I
    // believe it is more correct.
    SecurityManager sm = securityManager; // Be thread-safe!
    if (sm != null)
      sm.checkLink(libname);
    _load(libname, true);
  }

  /**
   * Return a localized version of this InputStream, meaning all characters
   * are localized before they come out the other end.
   *
   * @param in the stream to localize
   * @return the localized stream
   * @deprecated <code>InputStreamReader</code> is the preferred way to read
   *             local encodings
   */
  public InputStream getLocalizedInputStream(InputStream in)
  {
    return in;
  }

  /**
   * Return a localized version of this OutputStream, meaning all characters
   * are localized before they are sent to the other end.
   *
   * @param out the stream to localize
   * @return the localized stream
   * @deprecated <code>OutputStreamWriter</code> is the preferred way to write
   *             local encodings
   */
  public OutputStream getLocalizedOutputStream(OutputStream out)
  {
    return out;
  }

  /**
   * Native method that actually shuts down the virtual machine.
   *
   * @param status the status to end the process with
   */
  native void exitInternal(int status);

  /**
   * Load a file. If it has already been loaded, do nothing. The name has
   * already been mapped to a true filename.
   *
   * @param filename the file to load
   * @param do_search True if we should search the load path for the file
   */
  native void _load(String filename, boolean do_search);

  /**
   *This is a helper function for the ClassLoader which can load
   * compiled libraries.  Returns true if library (which is just the
   * base name -- path searching is done by this function) was loaded,
   * false otherwise.
   */
  native boolean loadLibraryInternal(String libname);

  /**
   * A helper for the constructor which does some internal native
   * initialization.
   */
  private native void init ();

  /**
   * Map a system-independent "short name" to the full file name, and append
   * it to the path.
   * XXX This method is being replaced by System.mapLibraryName.
   *
   * @param pathname the path
   * @param libname the short version of the library name
   * @return the full filename
   */
  static native String nativeGetLibname(String pathname, String libname);

  /**
   * Execute a process. The command line has already been tokenized, and
   * the environment should contain name=value mappings. If directory is null,
   * use the current working directory; otherwise start the process in that
   * directory.
   *
   * @param cmd the non-null command tokens
   * @param env the non-null environment setup
   * @param dir the directory to use, may be null
   * @return the newly created process
   * @throws NullPointerException if cmd or env have null elements
   */
  native Process execInternal(String[] cmd, String[] env, File dir);

  /**
   * Get the system properties. This is done here, instead of in System,
   * because of the bootstrap sequence. Note that the native code should
   * not try to use the Java I/O classes yet, as they rely on the properties
   * already existing. The only safe method to use to insert these default
   * system properties is {@link Properties#setProperty(String, String)}.
   *
   * <p>These properties MUST include:
   * <dl>
   * <dt>java.version         <dd>Java version number
   * <dt>java.vendor          <dd>Java vendor specific string
   * <dt>java.vendor.url      <dd>Java vendor URL
   * <dt>java.home            <dd>Java installation directory
   * <dt>java.vm.specification.version <dd>VM Spec version
   * <dt>java.vm.specification.vendor  <dd>VM Spec vendor
   * <dt>java.vm.specification.name    <dd>VM Spec name
   * <dt>java.vm.version      <dd>VM implementation version
   * <dt>java.vm.vendor       <dd>VM implementation vendor
   * <dt>java.vm.name         <dd>VM implementation name
   * <dt>java.specification.version    <dd>Java Runtime Environment version
   * <dt>java.specification.vendor     <dd>Java Runtime Environment vendor
   * <dt>java.specification.name       <dd>Java Runtime Environment name
   * <dt>java.class.version   <dd>Java class version number
   * <dt>java.class.path      <dd>Java classpath
   * <dt>java.library.path    <dd>Path for finding Java libraries
   * <dt>java.io.tmpdir       <dd>Default temp file path
   * <dt>java.compiler        <dd>Name of JIT to use
   * <dt>java.ext.dirs        <dd>Java extension path
   * <dt>os.name              <dd>Operating System Name
   * <dt>os.arch              <dd>Operating System Architecture
   * <dt>os.version           <dd>Operating System Version
   * <dt>file.separator       <dd>File separator ("/" on Unix)
   * <dt>path.separator       <dd>Path separator (":" on Unix)
   * <dt>line.separator       <dd>Line separator ("\n" on Unix)
   * <dt>user.name            <dd>User account name
   * <dt>user.home            <dd>User home directory
   * <dt>user.dir             <dd>User's current working directory
   * </dl>
   *
   * @param p the Properties object to insert the system properties into
   */
  static native void insertSystemProperties(Properties p);
} // class Runtime