| Methods Summary |
|---|
| public static native void | arraycopy(java.lang.Object src, int srcPos, java.lang.Object dest, int destPos, int length)Copies an array from the specified source array, beginning at the
specified position, to the specified position of the destination array.
A subsequence of array components are copied from the source
array referenced by src to the destination array
referenced by dest. The number of components copied is
equal to the length argument. The components at
positions srcPos through
srcPos+length-1 in the source array are copied into
positions destPos through
destPos+length-1, respectively, of the destination
array.
If the src and dest arguments refer to the
same array object, then the copying is performed as if the
components at positions srcPos through
srcPos+length-1 were first copied to a temporary
array with length components and then the contents of
the temporary array were copied into positions
destPos through destPos+length-1 of the
destination array.
If dest is null, then a
NullPointerException is thrown.
If src is null, then a
NullPointerException is thrown and the destination
array is not modified.
Otherwise, if any of the following is true, an
ArrayStoreException is thrown and the destination is
not modified:
- The
src argument refers to an object that is not an
array.
- The
dest argument refers to an object that is not an
array.
- The
src argument and dest argument refer
to arrays whose component types are different primitive types.
- The
src argument refers to an array with a primitive
component type and the dest argument refers to an array
with a reference component type.
- The
src argument refers to an array with a reference
component type and the dest argument refers to an array
with a primitive component type.
Otherwise, if any of the following is true, an
IndexOutOfBoundsException is
thrown and the destination is not modified:
- The
srcPos argument is negative.
- The
destPos argument is negative.
- The
length argument is negative.
srcPos+length is greater than
src.length, the length of the source array.
destPos+length is greater than
dest.length, the length of the destination array.
Otherwise, if any actual component of the source array from
position srcPos through
srcPos+length-1 cannot be converted to the component
type of the destination array by assignment conversion, an
ArrayStoreException is thrown. In this case, let
k be the smallest nonnegative integer less than
length such that src[srcPos+k]
cannot be converted to the component type of the destination
array; when the exception is thrown, source array components from
positions srcPos through
srcPos+k-1
will already have been copied to destination array positions
destPos through
destPos+k-1 and no other
positions of the destination array will have been modified.
(Because of the restrictions already itemized, this
paragraph effectively applies only to the situation where both
arrays have component types that are reference types.)
|
| private static void | checkIO()
if (security != null)
security.checkPermission(new RuntimePermission("setIO"));
|
| private static void | checkKey(java.lang.String key)
if (key == null) {
throw new NullPointerException("key can't be null");
}
if (key.equals("")) {
throw new IllegalArgumentException("key can't be empty");
}
|
| public static java.lang.String | clearProperty(java.lang.String key)Removes the system property indicated by the specified key.
First, if a security manager exists, its
SecurityManager.checkPermission method
is called with a PropertyPermission(key, "write")
permission. This may result in a SecurityException being thrown.
If no exception is thrown, the specified property is removed.
checkKey(key);
if (security != null)
security.checkPermission(new PropertyPermission(key, "write"));
return (String) props.remove(key);
|
| public static native long | currentTimeMillis()Returns the current time in milliseconds. Note that
while the unit of time of the return value is a millisecond,
the granularity of the value depends on the underlying
operating system and may be larger. For example, many
operating systems measure time in units of tens of
milliseconds.
See the description of the class Date for
a discussion of slight discrepancies that may arise between
"computer time" and coordinated universal time (UTC).
|
| public static void | exit(int status)Terminates the currently running Java Virtual Machine. The
argument serves as a status code; by convention, a nonzero status
code indicates abnormal termination.
This method calls the exit method in class
Runtime. This method never returns normally.
The call System.exit(n) is effectively equivalent to
the call:
Runtime.getRuntime().exit(n)
Runtime.getRuntime().exit(status);
|
| public static void | gc()Runs the garbage collector.
Calling the gc method suggests that the Java Virtual
Machine expend effort toward recycling unused objects in order to
make the memory they currently occupy available for quick reuse.
When control returns from the method call, the Java Virtual
Machine has made a best effort to reclaim space from all discarded
objects.
The call System.gc() is effectively equivalent to the
call:
Runtime.getRuntime().gc()
Runtime.getRuntime().gc();
|
| static java.lang.Class | getCallerClass()
// NOTE use of more generic Reflection.getCallerClass()
return Reflection.getCallerClass(3);
|
| public static java.util.Properties | getProperties()Determines the current system properties.
First, if there is a security manager, its
checkPropertiesAccess method is called with no
arguments. This may result in a security exception.
The current set of system properties for use by the
{@link #getProperty(String)} method is returned as a
Properties object. If there is no current set of
system properties, a set of system properties is first created and
initialized. This set of system properties always includes values
for the following keys:
| Key |
Description of Associated Value |
|---|
java.version |
Java Runtime Environment version |
java.vendor |
Java Runtime Environment vendor | java.vendor.url |
Java vendor URL |
java.home |
Java installation directory |
java.vm.specification.version |
Java Virtual Machine specification version |
java.vm.specification.vendor |
Java Virtual Machine specification vendor |
java.vm.specification.name |
Java Virtual Machine specification name |
java.vm.version |
Java Virtual Machine implementation version |
java.vm.vendor |
Java Virtual Machine implementation vendor |
java.vm.name |
Java Virtual Machine implementation name |
java.specification.version |
Java Runtime Environment specification version |
java.specification.vendor |
Java Runtime Environment specification vendor |
java.specification.name |
Java Runtime Environment specification name |
java.class.version |
Java class format version number |
java.class.path |
Java class path |
java.library.path |
List of paths to search when loading libraries |
java.io.tmpdir |
Default temp file path |
java.compiler |
Name of JIT compiler to use |
java.ext.dirs |
Path of extension directory or directories |
os.name |
Operating system name |
os.arch |
Operating system architecture |
os.version |
Operating system version |
file.separator |
File separator ("/" on UNIX) |
path.separator |
Path separator (":" on UNIX) |
line.separator |
Line separator ("\n" on UNIX) |
user.name |
User's account name |
user.home |
User's home directory |
user.dir |
User's current working directory |
Multiple paths in a system property value are separated by the path
separator character of the platform.
Note that even if the security manager does not permit the
getProperties operation, it may choose to permit the
{@link #getProperty(String)} operation.
if (security != null) {
security.checkPropertiesAccess();
}
return props;
|
| public static java.lang.String | getProperty(java.lang.String key)Gets the system property indicated by the specified key.
First, if there is a security manager, its
checkPropertyAccess method is called with the key as
its argument. This may result in a SecurityException.
If there is no current set of system properties, a set of system
properties is first created and initialized in the same manner as
for the getProperties method.
checkKey(key);
if (security != null) {
security.checkPropertyAccess(key);
}
return props.getProperty(key);
|
| public static java.lang.String | getProperty(java.lang.String key, java.lang.String def)Gets the system property indicated by the specified key.
First, if there is a security manager, its
checkPropertyAccess method is called with the
key as its argument.
If there is no current set of system properties, a set of system
properties is first created and initialized in the same manner as
for the getProperties method.
checkKey(key);
if (security != null) {
security.checkPropertyAccess(key);
}
return props.getProperty(key, def);
|
| public static java.lang.SecurityManager | getSecurityManager()Gets the system security interface.
return security;
|
| public static java.lang.String | getenv(java.lang.String name)Gets the value of the specified environment variable. An
environment variable is a system-dependent external named
value.
If a security manager exists, its
{@link SecurityManager#checkPermission checkPermission}
method is called with a
{@link RuntimePermission}("getenv."+name)
permission. This may result in a {@link SecurityException}
being thrown. If no exception is thrown the value of the
variable name is returned.
System
properties and environment variables are both
conceptually mappings between names and values. Both
mechanisms can be used to pass user-defined information to a
Java process. Environment variables have a more global effect,
because they are visible to all descendants of the process
which defines them, not just the immediate Java subprocess.
They can have subtly different semantics, such as case
insensitivity, on different operating systems. For these
reasons, environment variables are more likely to have
unintended side effects. It is best to use system properties
where possible. Environment variables should be used when a
global effect is desired, or when an external system interface
requires an environment variable (such as PATH).
On UNIX systems the alphabetic case of name is
typically significant, while on Microsoft Windows systems it is
typically not. For example, the expression
System.getenv("FOO").equals(System.getenv("foo"))
is likely to be true on Microsoft Windows.
if (security != null)
security.checkPermission(new RuntimePermission("getenv."+name));
return ProcessEnvironment.getenv(name);
|
| public static java.util.Map | getenv()Returns an unmodifiable string map view of the current system environment.
The environment is a system-dependent mapping from names to
values which is passed from parent to child processes.
If the system does not support environment variables, an
empty map is returned.
The returned map will never contain null keys or values.
Attempting to query the presence of a null key or value will
throw a {@link NullPointerException}. Attempting to query
the presence of a key or value which is not of type
{@link String} will throw a {@link ClassCastException}.
The returned map and its collection views may not obey the
general contract of the {@link Object#equals} and
{@link Object#hashCode} methods.
The returned map is typically case-sensitive on all platforms.
If a security manager exists, its
{@link SecurityManager#checkPermission checkPermission}
method is called with a
{@link RuntimePermission}("getenv.*")
permission. This may result in a {@link SecurityException} being
thrown.
When passing information to a Java subprocess,
system properties
are generally preferred over environment variables.
if (security != null)
security.checkPermission(new RuntimePermission("getenv.*"));
return ProcessEnvironment.getenv();
|
| public static native int | identityHashCode(java.lang.Object x)Returns the same hash code for the given object as
would be returned by the default method hashCode(),
whether or not the given object's class overrides
hashCode().
The hash code for the null reference is zero.
|
| public static java.nio.channels.Channel | inheritedChannel()Returns the channel inherited from the entity that created this
Java virtual machine.
This method returns the channel obtained by invoking the
{@link java.nio.channels.spi.SelectorProvider#inheritedChannel
inheritedChannel} method of the system-wide default
{@link java.nio.channels.spi.SelectorProvider} object.
In addition to the network-oriented channels described in
{@link java.nio.channels.spi.SelectorProvider#inheritedChannel
inheritedChannel}, this method may return other kinds of
channels in the future.
return SelectorProvider.provider().inheritedChannel();
|
| private static native java.util.Properties | initProperties(java.util.Properties props)
|
| private static void | initializeSystemClass()Initialize the system class. Called after thread initialization.
props = new Properties();
initProperties(props);
sun.misc.Version.init();
FileInputStream fdIn = new FileInputStream(FileDescriptor.in);
FileOutputStream fdOut = new FileOutputStream(FileDescriptor.out);
FileOutputStream fdErr = new FileOutputStream(FileDescriptor.err);
setIn0(new BufferedInputStream(fdIn));
setOut0(new PrintStream(new BufferedOutputStream(fdOut, 128), true));
setErr0(new PrintStream(new BufferedOutputStream(fdErr, 128), true));
// Load the zip library now in order to keep java.util.zip.ZipFile
// from trying to use itself to load this library later.
loadLibrary("zip");
// Currently File.deleteOnExit is built on JVM_Exit, which is a
// separate mechanism from shutdown hooks. Unfortunately in order to
// work properly JVM_Exit implicitly requires that Java signal
// handlers be set up for HUP, TERM, and INT (where available). If
// File.deleteOnExit were implemented in terms of shutdown hooks this
// call to Terminator.setup() could be removed.
Terminator.setup();
// Set the maximum amount of direct memory. This value is controlled
// by the vm option -XX:MaxDirectMemorySize=<size>. This method acts
// as an initializer only if it is called before sun.misc.VM.booted().
sun.misc.VM.maxDirectMemory();
// Set a boolean to determine whether ClassLoader.loadClass accepts
// array syntax. This value is controlled by the system property
// "sun.lang.ClassLoader.allowArraySyntax". This method acts as
// an initializer only if it is called before sun.misc.VM.booted().
sun.misc.VM.allowArraySyntax();
// Subsystems that are invoked during initialization can invoke
// sun.misc.VM.isBooted() in order to avoid doing things that should
// wait until the application class loader has been set up.
sun.misc.VM.booted();
// The main thread is not added to its thread group in the same
// way as other threads; we must do it ourselves here.
Thread current = Thread.currentThread();
current.getThreadGroup().add(current);
// Allow privileged classes outside of java.lang
sun.misc.SharedSecrets.setJavaLangAccess(new sun.misc.JavaLangAccess(){
public sun.reflect.ConstantPool getConstantPool(Class klass) {
return klass.getConstantPool();
}
public void setAnnotationType(Class klass, AnnotationType type) {
klass.setAnnotationType(type);
}
public AnnotationType getAnnotationType(Class klass) {
return klass.getAnnotationType();
}
});
|
| public static void | load(java.lang.String filename)Loads a code file with the specified filename from the local file
system as a dynamic library. The filename
argument must be a complete path name.
The call System.load(name) is effectively equivalent
to the call:
Runtime.getRuntime().load(name)
Runtime.getRuntime().load0(getCallerClass(), filename);
|
| public static void | loadLibrary(java.lang.String libname)Loads the system library specified by the libname
argument. The manner in which a library name is mapped to the
actual system library is system dependent.
The call System.loadLibrary(name) is effectively
equivalent to the call
Runtime.getRuntime().loadLibrary(name)
Runtime.getRuntime().loadLibrary0(getCallerClass(), libname);
|
| public static native java.lang.String | mapLibraryName(java.lang.String libname)Maps a library name into a platform-specific string representing
a native library.
|
| public static native long | nanoTime()Returns the current value of the most precise available system
timer, in nanoseconds.
This method can only be used to measure elapsed time and is
not related to any other notion of system or wall-clock time.
The value returned represents nanoseconds since some fixed but
arbitrary time (perhaps in the future, so values may be
negative). This method provides nanosecond precision, but not
necessarily nanosecond accuracy. No guarantees are made about
how frequently values change. Differences in successive calls
that span greater than approximately 292 years (263
nanoseconds) will not accurately compute elapsed time due to
numerical overflow.
For example, to measure how long some code takes to execute:
long startTime = System.nanoTime();
// ... the code being measured ...
long estimatedTime = System.nanoTime() - startTime;
|
| private static java.io.InputStream | nullInputStream()The following two methods exist because in, out, and err must be
initialized to null. The compiler, however, cannot be permitted to
inline access to them, since they are later set to more sensible values
by initializeSystemClass().
if (currentTimeMillis() > 0)
return null;
throw new NullPointerException();
|
| private static java.io.PrintStream | nullPrintStream()
if (currentTimeMillis() > 0)
return null;
throw new NullPointerException();
|
| private static native void | registerNatives()
|
| public static void | runFinalization()Runs the finalization methods of any objects pending finalization.
Calling this method suggests that the Java Virtual Machine expend
effort toward running the finalize methods of objects
that have been found to be discarded but whose finalize
methods have not yet been run. When control returns from the
method call, the Java Virtual Machine has made a best effort to
complete all outstanding finalizations.
The call System.runFinalization() is effectively
equivalent to the call:
Runtime.getRuntime().runFinalization()
Runtime.getRuntime().runFinalization();
|
| public static void | runFinalizersOnExit(boolean value)Enable or disable finalization on exit; doing so specifies that the
finalizers of all objects that have finalizers that have not yet been
automatically invoked are to be run before the Java runtime exits.
By default, finalization on exit is disabled.
If there is a security manager,
its checkExit method is first called
with 0 as its argument to ensure the exit is allowed.
This could result in a SecurityException.
Runtime.getRuntime().runFinalizersOnExit(value);
|
| public static void | setErr(java.io.PrintStream err)Reassigns the "standard" error output stream.
First, if there is a security manager, its checkPermission
method is called with a RuntimePermission("setIO") permission
to see if it's ok to reassign the "standard" error output stream.
checkIO();
setErr0(err);
|
| private static native void | setErr0(java.io.PrintStream err)
|
| public static void | setIn(java.io.InputStream in)Reassigns the "standard" input stream.
First, if there is a security manager, its checkPermission
method is called with a RuntimePermission("setIO") permission
to see if it's ok to reassign the "standard" input stream.
checkIO();
setIn0(in);
|
| private static native void | setIn0(java.io.InputStream in)
|
| public static void | setOut(java.io.PrintStream out)Reassigns the "standard" output stream.
First, if there is a security manager, its checkPermission
method is called with a RuntimePermission("setIO") permission
to see if it's ok to reassign the "standard" output stream.
checkIO();
setOut0(out);
|
| private static native void | setOut0(java.io.PrintStream out)
|
| public static void | setProperties(java.util.Properties props)Sets the system properties to the Properties
argument.
First, if there is a security manager, its
checkPropertiesAccess method is called with no
arguments. This may result in a security exception.
The argument becomes the current set of system properties for use
by the {@link #getProperty(String)} method. If the argument is
null, then the current set of system properties is
forgotten.
if (security != null) {
security.checkPropertiesAccess();
}
if (props == null) {
props = new Properties();
initProperties(props);
}
System.props = props;
|
| public static java.lang.String | setProperty(java.lang.String key, java.lang.String value)Sets the system property indicated by the specified key.
First, if a security manager exists, its
SecurityManager.checkPermission method
is called with a PropertyPermission(key, "write")
permission. This may result in a SecurityException being thrown.
If no exception is thrown, the specified property is set to the given
value.
checkKey(key);
if (security != null)
security.checkPermission(new PropertyPermission(key,
SecurityConstants.PROPERTY_WRITE_ACTION));
return (String) props.setProperty(key, value);
|
| public static void | setSecurityManager(java.lang.SecurityManager s)Sets the System security.
If there is a security manager already installed, this method first
calls the security manager's checkPermission method
with a RuntimePermission("setSecurityManager")
permission to ensure it's ok to replace the existing
security manager.
This may result in throwing a SecurityException.
Otherwise, the argument is established as the current
security manager. If the argument is null and no
security manager has been established, then no action is taken and
the method simply returns.
try {
s.checkPackageAccess("java.lang");
} catch (Exception e) {
// no-op
}
setSecurityManager0(s);
|
| private static synchronized void | setSecurityManager0(java.lang.SecurityManager s)
if (security != null) {
// ask the currently installed security manager if we
// can replace it.
security.checkPermission(new RuntimePermission
("setSecurityManager"));
}
if ((s != null) && (s.getClass().getClassLoader() != null)) {
// New security manager class is not on bootstrap classpath.
// Cause policy to get initialized before we install the new
// security manager, in order to prevent infinite loops when
// trying to initialize the policy (which usually involves
// accessing some security and/or system properties, which in turn
// calls the installed security manager's checkPermission method
// which will loop infinitely if there is a non-system class
// (in this case: the new security manager class) on the stack).
AccessController.doPrivileged(new PrivilegedAction() {
public Object run() {
s.getClass().getProtectionDomain().implies
(SecurityConstants.ALL_PERMISSION);
return null;
}
});
}
security = s;
InetAddressCachePolicy.setIfNotSet(InetAddressCachePolicy.FOREVER);
|
