This corresponds to the C stdin and C++ cin variables, which * typically input from the keyboard, but may be used to pipe input from * other processes or files. That should all be transparent to you, * however. */ public static final InputStream in = VMSystem.makeStandardInputStream(); /** * The standard output PrintStream. This is assigned at startup and * starts its life perfectly valid. Although it is marked final, you can * change it using {@link #setOut(PrintStream)} through some hefty VM magic. * *
This corresponds to the C stdout and C++ cout variables, which * typically output normal messages to the screen, but may be used to pipe * output to other processes or files. That should all be transparent to * you, however. */ public static final PrintStream out = VMSystem.makeStandardOutputStream(); /** * The standard output PrintStream. This is assigned at startup and * starts its life perfectly valid. Although it is marked final, you can * change it using {@link #setErr(PrintStream)} through some hefty VM magic. * *
This corresponds to the C stderr and C++ cerr variables, which
* typically output error messages to the screen, but may be used to pipe
* output to other processes or files. That should all be transparent to
* you, however.
*/
public static final PrintStream err = VMSystem.makeStandardErrorStream();
/**
* A cached copy of the environment variable map.
*/
private static Map
* Returns the current value of a nanosecond-precise system timer.
* The value of the timer is an offset relative to some arbitrary fixed
* time, which may be in the future (making the value negative). This
* method is useful for timing events where nanosecond precision is
* required. This is achieved by calling this method before and after the
* event, and taking the difference betweent the two times:
*
*
* Note that the value is only nanosecond-precise, and not accurate; there
* is no guarantee that the difference between two values is really a
* nanosecond. Also, the value is prone to overflow if the offset
* exceeds 2^63.
* The required properties include:
*
* Returns an unmodifiable view of the system environment variables.
* If the underlying system does not support environment variables,
* an empty map is returned.
*
* The returned map is read-only and does not accept queries using
* null keys or values, or those of a type other than
* As the returned map is generated using data from the underlying
* platform, it may not comply with the
* Use of this method may require a security check for the
* RuntimePermission "getenv.*".
*
* The library is loaded using the class loader associated with the
* class associated with the invoking method.
*
* @param filename the code file to load
* @throws SecurityException if permission is denied
* @throws UnsatisfiedLinkError if the file cannot be loaded
* @see Runtime#load(String)
*/
public static void load(String filename)
{
Runtime.getRuntime().load(filename, VMStackWalker.getCallingClassLoader());
}
/**
* Load a library using its explicit system-dependent filename. A security
* check may be performed,
* The library is loaded using the class loader associated with the
* class associated with the invoking method.
*
* @param libname the library file to load
* @throws SecurityException if permission is denied
* @throws UnsatisfiedLinkError if the file cannot be loaded
* @see Runtime#load(String)
*/
public static void loadLibrary(String libname)
{
Runtime.getRuntime().loadLibrary(libname,
VMStackWalker.getCallingClassLoader());
}
/**
* Convert a library name to its platform-specific variant.
*
* @param libname the library name, as used in RuntimePermission("setIO").
*
* @param in the new InputStream
* @throws SecurityException if permission is denied
* @since 1.1
*/
public static void setIn(InputStream in)
{
SecurityManager sm = SecurityManager.current; // Be thread-safe.
if (sm != null)
sm.checkPermission(new RuntimePermission("setIO"));
VMSystem.setIn(in);
}
/**
* Set {@link #out} to a new PrintStream. This uses some VM magic to change
* a "final" variable, so naturally there is a security check,
* RuntimePermission("setIO").
*
* @param out the new PrintStream
* @throws SecurityException if permission is denied
* @since 1.1
*/
public static void setOut(PrintStream out)
{
SecurityManager sm = SecurityManager.current; // Be thread-safe.
if (sm != null)
sm.checkPermission(new RuntimePermission("setIO"));
VMSystem.setOut(out);
}
/**
* Set {@link #err} to a new PrintStream. This uses some VM magic to change
* a "final" variable, so naturally there is a security check,
* RuntimePermission("setIO").
*
* @param err the new PrintStream
* @throws SecurityException if permission is denied
* @since 1.1
*/
public static void setErr(PrintStream err)
{
SecurityManager sm = SecurityManager.current; // Be thread-safe.
if (sm != null)
sm.checkPermission(new RuntimePermission("setIO"));
VMSystem.setErr(err);
}
/**
* Set the current SecurityManager. If a security manager already exists,
* then RuntimePermission("setSecurityManager") is checked
* first. Since this permission is denied by the default security manager,
* setting the security manager is often an irreversible action.
*
* Spec Note: Don't ask me, I didn't write it. It looks
* pretty vulnerable; whoever gets to the gate first gets to set the policy.
* There is probably some way to set the original security manager as a
* command line argument to the VM, but I don't know it.
*
* @param sm the new SecurityManager
* @throws SecurityException if permission is denied
*/
public static synchronized void setSecurityManager(SecurityManager sm)
{
// Implementation note: the field lives in SecurityManager because of
// bootstrap initialization issues. This method is synchronized so that
// no other thread changes it to null before this thread makes the change.
if (SecurityManager.current != null)
SecurityManager.current.checkPermission
(new RuntimePermission("setSecurityManager"));
// java.security.Security's class initialiser loads and parses the
// policy files. If it hasn't been run already it will be run
// during the first permission check. That initialisation will
// fail if a very restrictive security manager is in force, so we
// preload it here.
if (SecurityManager.current == null)
{
try
{
Class.forName("java.security.Security");
}
catch (ClassNotFoundException e)
{
}
}
SecurityManager.current = sm;
}
/**
* Get the current SecurityManager. If the SecurityManager has not been
* set yet, then this method returns null.
*
* @return the current SecurityManager, or null
*/
public static SecurityManager getSecurityManager()
{
return SecurityManager.current;
}
/**
* Get the current time, measured in the number of milliseconds from the
* beginning of Jan. 1, 1970. This is gathered from the system clock, with
* any attendant incorrectness (it may be timezone dependent).
*
* @return the current time
* @see java.util.Date
*/
public static long currentTimeMillis()
{
return VMSystem.currentTimeMillis();
}
/**
* long startTime = System.nanoTime();
* ...
* long endTime = System.nanoTime();
* long duration = endTime - startTime;
* src[srcStart] ...
* src[srcStart+len-1] to dest[destStart] ...
* dest[destStart+len-1]. First, the arguments are validated:
* neither array may be null, they must be of compatible types, and the
* start and length must fit within both arrays. Then the copying starts,
* and proceeds through increasing slots. If src and dest are the same
* array, this will appear to copy the data to a temporary location first.
* An ArrayStoreException in the middle of copying will leave earlier
* elements copied, but later elements unchanged.
*
* @param src the array to copy elements from
* @param srcStart the starting position in src
* @param dest the array to copy elements to
* @param destStart the starting position in dest
* @param len the number of elements to copy
* @throws NullPointerException if src or dest is null
* @throws ArrayStoreException if src or dest is not an array, if they are
* not compatible array types, or if an incompatible runtime type
* is stored in dest
* @throws IndexOutOfBoundsException if len is negative, or if the start or
* end copy position in either array is out of bounds
*/
public static void arraycopy(Object src, int srcStart,
Object dest, int destStart, int len)
{
VMSystem.arraycopy(src, srcStart, dest, destStart, len);
}
/**
* Get a hash code computed by the VM for the Object. This hash code will
* be the same as Object's hashCode() method. It is usually some
* convolution of the pointer to the Object internal to the VM. It
* follows standard hash code rules, in that it will remain the same for a
* given Object for the lifetime of that Object.
*
* @param o the Object to get the hash code for
* @return the VM-dependent hash code for this Object
* @since 1.1
*/
public static int identityHashCode(Object o)
{
return VMSystem.identityHashCode(o);
}
/**
* Get all the system properties at once. A security check may be performed,
* checkPropertiesAccess. Note that a security manager may
* allow getting a single property, but not the entire group.
*
*
*
*
* In addition, gnu defines several other properties, where ? stands for
* each character in '0' through '9':
*
*
*
* @return the system properties, will never be null
* @throws SecurityException if permission is denied
*/
public static Properties getProperties()
{
SecurityManager sm = SecurityManager.current; // Be thread-safe.
if (sm != null)
sm.checkPropertiesAccess();
return SystemProperties.getProperties();
}
/**
* Set all the system properties at once. A security check may be performed,
* checkPropertiesAccess. Note that a security manager may
* allow setting a single property, but not the entire group. An argument
* of null resets the properties to the startup default.
*
* @param properties the new set of system properties
* @throws SecurityException if permission is denied
*/
public static void setProperties(Properties properties)
{
SecurityManager sm = SecurityManager.current; // Be thread-safe.
if (sm != null)
sm.checkPropertiesAccess();
SystemProperties.setProperties(properties);
}
/**
* Get a single system property by name. A security check may be performed,
* checkPropertyAccess(key).
*
* @param key the name of the system property to get
* @return the property, or null if not found
* @throws SecurityException if permission is denied
* @throws NullPointerException if key is null
* @throws IllegalArgumentException if key is ""
*/
public static String getProperty(String key)
{
SecurityManager sm = SecurityManager.current; // Be thread-safe.
if (sm != null)
sm.checkPropertyAccess(key);
if (key.length() == 0)
throw new IllegalArgumentException("key can't be empty");
return SystemProperties.getProperty(key);
}
/**
* Get a single system property by name. A security check may be performed,
* checkPropertyAccess(key).
*
* @param key the name of the system property to get
* @param def the default
* @return the property, or def if not found
* @throws SecurityException if permission is denied
* @throws NullPointerException if key is null
* @throws IllegalArgumentException if key is ""
*/
public static String getProperty(String key, String def)
{
SecurityManager sm = SecurityManager.current; // Be thread-safe.
if (sm != null)
sm.checkPropertyAccess(key);
// This handles both the null pointer exception and the illegal
// argument exception.
if (key.length() == 0)
throw new IllegalArgumentException("key can't be empty");
return SystemProperties.getProperty(key, def);
}
/**
* Set a single system property by name. A security check may be performed,
* checkPropertyAccess(key, "write").
*
* @param key the name of the system property to set
* @param value the new value
* @return the previous value, or null
* @throws SecurityException if permission is denied
* @throws NullPointerException if key is null
* @throws IllegalArgumentException if key is ""
* @since 1.2
*/
public static String setProperty(String key, String value)
{
SecurityManager sm = SecurityManager.current; // Be thread-safe.
if (sm != null)
sm.checkPermission(new PropertyPermission(key, "write"));
// This handles both the null pointer exception and the illegal
// argument exception.
if (key.length() == 0)
throw new IllegalArgumentException("key can't be empty");
return SystemProperties.setProperty(key, value);
}
/**
* Remove a single system property by name. A security check may be
* performed, checkPropertyAccess(key, "write").
*
* @param key the name of the system property to remove
* @return the previous value, or null
* @throws SecurityException if permission is denied
* @throws NullPointerException if key is null
* @throws IllegalArgumentException if key is ""
* @since 1.5
*/
public static String clearProperty(String key)
{
SecurityManager sm = SecurityManager.current; // Be thread-safe.
if (sm != null)
sm.checkPermission(new PropertyPermission(key, "write"));
// This handles both the null pointer exception and the illegal
// argument exception.
if (key.length() == 0)
throw new IllegalArgumentException("key can't be empty");
return SystemProperties.remove(key);
}
/**
* Gets the value of an environment variable.
*
* @param name the name of the environment variable
* @return the string value of the variable or null when the
* environment variable is not defined.
* @throws NullPointerException
* @throws SecurityException if permission is denied
* @since 1.5
* @specnote This method was deprecated in some JDK releases, but
* was restored in 1.5.
*/
public static String getenv(String name)
{
if (name == null)
throw new NullPointerException();
SecurityManager sm = SecurityManager.current; // Be thread-safe.
if (sm != null)
sm.checkPermission(new RuntimePermission("getenv." + name));
return VMSystem.getenv(name);
}
/**
* String.
* Attempts to modify the map will throw an
* UnsupportedOperationException, while attempts
* to pass in a null value will throw a
* NullPointerException. Types other than String
* throw a ClassCastException.
* equals()
* and hashCode() contracts. It is also likely that
* the keys of this map will be case-sensitive.
* Runtime.getRuntime().exit(status), and never returns.
* Obviously, a security check is in order, checkExit.
*
* @param status the exit status; by convention non-zero is abnormal
* @throws SecurityException if permission is denied
* @see Runtime#exit(int)
*/
public static void exit(int status)
{
Runtime.getRuntime().exit(status);
}
/**
* Calls the garbage collector. This is only a hint, and it is up to the
* implementation what this hint suggests, but it usually causes a
* best-effort attempt to reclaim unused memory from discarded objects.
* This calls Runtime.getRuntime().gc().
*
* @see Runtime#gc()
*/
public static void gc()
{
Runtime.getRuntime().gc();
}
/**
* Runs object finalization on pending objects. This is only a hint, and
* it is up to the implementation what this hint suggests, but it usually
* causes a best-effort attempt to run finalizers on all objects ready
* to be reclaimed. This calls
* Runtime.getRuntime().runFinalization().
*
* @see Runtime#runFinalization()
*/
public static void runFinalization()
{
Runtime.getRuntime().runFinalization();
}
/**
* Tell the Runtime whether to run finalization before exiting the
* JVM. This is inherently unsafe in multi-threaded applications,
* since it can force initialization on objects which are still in use
* by live threads, leading to deadlock; therefore this is disabled by
* default. There may be a security check, checkExit(0). This
* calls Runtime.runFinalizersOnExit().
*
* @param finalizeOnExit whether to run finalizers on exit
* @throws SecurityException if permission is denied
* @see Runtime#runFinalizersOnExit(boolean)
* @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)
{
Runtime.runFinalizersOnExit(finalizeOnExit);
}
/**
* Load a code file using its explicit system-dependent filename. A security
* check may be performed, checkLink. This just calls
* Runtime.getRuntime().load(filename).
*
* checkLink. This just calls
* Runtime.getRuntime().load(filename).
*
* loadLibrary
* @return the platform-specific mangling of the name
* @since 1.2
*/
public static String mapLibraryName(String libname)
{
return VMRuntime.mapLibraryName(libname);
}
/**
* Returns the inherited channel of the VM.
*
* This wraps the inheritedChannel() call of the system's default
* {@link SelectorProvider}.
*
* @return the inherited channel of the VM
*
* @throws IOException If an I/O error occurs
* @throws SecurityException If an installed security manager denies access
* to RuntimePermission("inheritedChannel")
*
* @since 1.5
*/
public static Channel inheritedChannel()
throws IOException
{
return SelectorProvider.provider().inheritedChannel();
}
/**
* This is a specialised Collection, providing
* the necessary provisions for the collections used by the
* environment variable map. Namely, it prevents
* querying anything but Strings.
*
* @author Andrew John Hughes (gnu_andrew@member.fsf.org)
*/
private static class EnvironmentCollection
extends AbstractCollectionString. All other queries
* are forwarded to the underlying collection.
*
* @param obj the object to look for.
* @return true if the object exists in the collection.
* @throws NullPointerException if the specified object is null.
* @throws ClassCastException if the specified object is not a String.
*/
public boolean contains(Object obj)
{
if (obj == null)
throw new
NullPointerException("This collection does not support " +
"null values.");
if (!(obj instanceof String))
throw new
ClassCastException("This collection only supports Strings.");
return c.contains(obj);
}
/**
* Blocks queries where the collection contains a null object or
* an object which isn't of type String. All other
* queries are forwarded to the underlying collection.
*
* @param coll the collection of objects to look for.
* @return true if the collection contains all elements in the collection.
* @throws NullPointerException if the collection is null.
* @throws NullPointerException if any collection entry is null.
* @throws ClassCastException if any collection entry is not a String.
*/
public boolean containsAll(Collection coll)
{
for (Object o: coll)
{
if (o == null)
throw new
NullPointerException("This collection does not support " +
"null values.");
if (!(o instanceof String))
throw new
ClassCastException("This collection only supports Strings.");
}
return c.containsAll(coll);
}
/**
* This returns an iterator over the map elements, with the
* same provisions as for the collection and underlying map.
*
* @return an iterator over the map elements.
*/
public IteratorHashMap, which
* prevents the addition or querying of anything other than
* String objects.
*
* @author Andrew John Hughes (gnu_andrew@member.fsf.org)
*/
static class EnvironmentMap
extends HashMapEnvironmentMap.
*/
EnvironmentMap()
{
super();
}
/**
* Constructs a new EnvironmentMap containing
* the contents of the specified map.
*
* @param m the map to be added to this.
* @throws NullPointerException if a key or value is null.
* @throws ClassCastException if a key or value is not a String.
*/
EnvironmentMap(MapString. All other queries
* are forwarded to the superclass.
*
* @param key the key to look for in the map.
* @return true if the key exists in the map.
* @throws NullPointerException if the specified key is null.
*/
public boolean containsKey(Object key)
{
if (key == null)
throw new
NullPointerException("This map does not support null keys.");
if (!(key instanceof String))
throw new
ClassCastException("This map only allows queries using Strings.");
return super.containsKey(key);
}
/**
* Blocks queries using a null or non-String value.
* All other queries are forwarded to the superclass.
*
* @param value the value to look for in the map.
* @return true if the value exists in the map.
* @throws NullPointerException if the specified value is null.
*/
public boolean containsValue(Object value)
{
if (value == null)
throw new
NullPointerException("This map does not support null values.");
if (!(value instanceof String))
throw new
ClassCastException("This map only allows queries using Strings.");
return super.containsValue(value);
}
/**
* Returns a set view of the map entries, with the same
* provisions as for the underlying map.
*
* @return a set containing the map entries.
*/
public SetString key.
* All other queries are passed on to the superclass.
*
* @param key the key to retrieve the value for.
* @return the value associated with the given key.
* @throws NullPointerException if the specified key is null.
* @throws ClassCastException if the specified key is not a String.
*/
public String get(Object key)
{
if (key == null)
throw new
NullPointerException("This map does not support null keys.");
if (!(key instanceof String))
throw new
ClassCastException("This map only allows queries using Strings.");
return super.get(key);
}
/**
* Returns a set view of the keys, with the same
* provisions as for the underlying map.
*
* @return a set containing the keys.
*/
public SetString.
*
* @param key the key of the entry to remove.
* @return the removed value.
* @throws NullPointerException if the specified key is null.
* @throws ClassCastException if the specified key is not a String.
*/
public String remove(Object key)
{
if (key == null)
throw new
NullPointerException("This map does not support null keys.");
if (!(key instanceof String))
throw new
ClassCastException("This map only allows queries using Strings.");
return super.remove(key);
}
/**
* Returns a collection view of the values, with the same
* provisions as for the underlying map.
*
* @return a collection containing the values.
*/
public CollectionSet, providing
* the necessary provisions for the collections used by the
* environment variable map. Namely, it prevents
* modifications and the use of queries with null
* or non-String values.
*
* @author Andrew John Hughes (gnu_andrew@member.fsf.org)
*/
private static class EnvironmentSet
extends EnvironmentCollection
implements Set