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java.lang.Object | +----java.lang.Thread
Every thread has a priority. Threads with higher priority are
executed in preference to threads with lower priority. Each thread
may or may not also be marked as a daemon. When code running in
some thread creates a new Thread object, the new
thread has its priority initially set equal to the priority of the
creating thread, and is a daemon thread if and only if the
creating thread is a daemon.
When a Java Virtual Machine starts up, there is usually a single
non-daemon thread (which typically calls the method named
main of some designated class). The Java Virtual
Machine continues to execute threads until either of the following
occurs:
exit method of class Runtime has been
called and the security manager has permitted the exit operation
to take place.
run method or by
performing the stop method.
There are two ways to create a new thread of execution. One is to
declare a class to be a subclass of Thread. This
subclass should override the run method of class
Thread. An instance of the subclass can then be
allocated and started. For example, a thread that computes primes
larger than a stated value could be written as follows:
class PrimeThread extends Thread {
long minPrime;
PrimeThread(long minPrime) {
this.minPrime = minPrime;
}
public void run() {
// compute primes larger than minPrime
. . .
}
}
The following code would then create a thread and start it running:
PrimeThread p = new PrimeThread(143);
p.start();
The other way to create a thread is to declare a class that
implements the Runnable interface. That class then
implements the run method. An instance of the class can
then be allocated, passed as an argument when creating
Thread, and started. The same example in this other
style looks like the following:
class PrimeRun implements Runnable {
long minPrime;
PrimeRun(long minPrime) {
this.minPrime = minPrime;
}
public void run() {
// compute primes larger than minPrime
. . .
}
}
The following code would then create a thread and start it running:
PrimeRun p = new PrimeRun(143);
new Thread(p).start();
Every thread has a name for identification purposes. More than one thread may have the same name. If a name is not specified when a thread is created, a new name is generated for it.
MAX_PRIORITY
MIN_PRIORITY
NORM_PRIORITY
Thread()
Thread object.
Thread(Runnable)
Thread object.
Thread(Runnable, String)
Thread object.
Thread(String)
Thread object.
Thread(ThreadGroup, Runnable)
Thread object.
Thread(ThreadGroup, Runnable, String)
Thread object so that it has
target as its run object, has the specified
name as its name, and belongs to the thread group
referred to by group.
Thread(ThreadGroup, String)
Thread object.
activeCount()
checkAccess()
countStackFrames()
currentThread()
destroy()
dumpStack()
enumerate(Thread[])
getName()
getPriority()
getThreadGroup()
interrupt()
interrupted()
isAlive()
isDaemon()
isInterrupted()
join()
join(long)
millis milliseconds for this thread to
die.
join(long, int)
millis milliseconds plus
nanos nanoseconds for this thread to die.
resume()
run()
Runnable run object, then that
Runnable object's run method is called;
otherwise, this method does nothing and returns.
setDaemon(boolean)
setName(String)
name.
setPriority(int)
sleep(long)
sleep(long, int)
start()
run method of this thread.
stop()
stop(Throwable)
suspend()
toString()
yield()
MIN_PRIORITY
public static final int MIN_PRIORITY
NORM_PRIORITY
public static final int NORM_PRIORITY
MAX_PRIORITY
public static final int MAX_PRIORITY
Thread
public Thread()
Thread object. This constructor has
the same effect as Thread(null, null,
gname), where gname is
a newly generated name. Automatically generated names are of the
form "Thread-"+n, where n is an integer.
Threads created this way must have overridden their
run() method to actually do anything. An example
illustrating this method being used follows:
import java.lang.*;
class plain01 implements Runnable {
String name;
plain01() {
name = null;
}
plain01(String s) {
name = s;
}
public void run() {
if (name == null)
System.out.println("A new thread created");
else
System.out.println("A new thread with name " + name +
" created");
}
}
class threadtest01 {
public static void main(String args[] ) {
int failed = 0 ;
Thread t1 = new Thread();
if (t1 != null)
System.out.println("new Thread() succeed");
else {
System.out.println("new Thread() failed");
failed++;
}
}
}
Thread
public Thread(Runnable target)
Thread object. This constructor has
the same effect as Thread(null, target,
gname), where gname is
a newly generated name. Automatically generated names are of the
form "Thread-"+n, where n is an integer.
run method is called.
Thread
public Thread(ThreadGroup group,
Runnable target)
Thread object. This constructor has
the same effect as Thread(group, target,
gname), where gname is
a newly generated name. Automatically generated names are of the
form "Thread-"+n, where n is an integer.
run method is called.
Thread
public Thread(String name)
Thread object. This constructor has
the same effect as Thread(null, null, name).
Thread
public Thread(ThreadGroup group,
String name)
Thread object. This constructor has
the same effect as Thread(group, null, name)
Thread
public Thread(Runnable target,
String name)
Thread object. This constructor has
the same effect as Thread(null, target, name).
run method is called.
Thread
public Thread(ThreadGroup group,
Runnable target,
String name)
Thread object so that it has
target as its run object, has the specified
name as its name, and belongs to the thread group
referred to by group.
If group is not null, the
checkAccess method of that thread group is called with
no arguments; this may result in throwing a
SecurityException; if group is
null, the new process belongs to the same group as
the thread that is creating the new thread.
If the target argument is not null, the
run method of the target is called when
this thread is started. If the target argument is
null, this thread's run method is called
when this thread is started.
The priority of the newly created thread is set equal to the
priority of the thread creating it, that is, the currently running
thread. The method setPriority may be used to
change the priority to a new value.
The newly created thread is initially marked as being a daemon
thread if and only if the thread creating it is currently marked
as a daemon thread. The method setDaemon may be used
to change whether or not a thread is a daemon.
run method is called.
currentThread
public static native Thread currentThread()
yield
public static native void yield()
sleep
public static native void sleep(long millis) throws InterruptedException
sleep
public static void sleep(long millis,
int nanos) throws InterruptedException
start
public native synchronized void start()
run method of this thread.
The result is that two threads are running concurrently: the
current thread (which returns from the call to the
start method) and the other thread (which executes its
run method).
run
public void run()
Runnable run object, then that
Runnable object's run method is called;
otherwise, this method does nothing and returns.
Subclasses of Thread should override this method.
stop
public final void stop()
First, the checkAccess method of this thread is called
with no arguments. This may result in throwing a
SecurityException (in the current thread).
The thread represented by this thread is forced to stop whatever
it is doing abnormally and to throw a newly created
ThreadDeath object as an exception.
It is permitted to stop a thread that has not yet been started. If the thread is eventually started, it immediately terminates.
An application should not normally try to catch
ThreadDeath unless it must do some extraordinary
cleanup operation (note that the throwing of
ThreadDeath causes finally clauses of
try statements to be executed before the thread
officially dies). If a catch clause catches a
ThreadDeath object, it is important to rethrow the
object so that the thread actually dies.
The top-level error handler that reacts to otherwise uncaught
exceptions does not print out a message or otherwise notify the
application if the uncaught exception is an instance of
ThreadDeath.
Note: the use of this method is unsafe as it can result in the
corruption of invariants. Stopping a thread with Thread.stop causes
it to unlock all of the monitors that it has locked (as a natural
consequence of the unchecked ThreadDeath exception
propagating up the stack). If any of the objects previously protected
by these monitors were in an inconsistent state, the damaged objects
become visible to other threads potentially resulting in arbitrary
behaviour. Many uses of stop should be replaced by code
that simply modifies some volatile variable to indicate that the target
thread should stop running. The target thread should check this
variable regularly, and return from its run method in an orderly
fashion if the variable indicates that it is to stop running. If the
target thread waits for long periods, the interrupt method should be
used to interrupt the wait.
stop
public final synchronized void stop(Throwable o)
First, the checkAccess method of this thread is called
with no arguments. This may result in throwing a
SecurityException (in the current thread).
If the argument obj is null, a
NullPointerException is thrown (in the current thread).
The thread represented by this thread is forced to complete
whatever it is doing abnormally and to throw the
Throwable object obj as an exception. This
is an unusual action to take; normally, the stop method
that takes no arguments should be used.
It is permitted to stop a thread that has not yet been started. If the thread is eventually started, it immediately terminates.
interrupt
public void interrupt()
interrupted
public static boolean interrupted()
interrupted is a static method, while
isInterrupted is called on the current
Thread instance.
true if the current thread has been interrupted;
false otherwise.
isInterrupted
public boolean isInterrupted()
isInterrupted
is called on the current Thread instance; by
contrast, interrupted is a static method.
true if this thread has been interrupted;
false otherwise.
destroy
public void destroy()
isAlive
public final native boolean isAlive()
true if this thread is alive;
false otherwise.
suspend
public final void suspend()
First, the checkAccess method of this thread is called
with no arguments. This may result in throwing a
SecurityException (in the current thread).
If the thread is alive, it is suspended and makes no further progress unless and until it is resumed.
resume
public final void resume()
First, the checkAccess method of this thread is called
with no arguments. This may result in throwing a
SecurityException(in the current thread).
If the thread is alive but suspended, it is resumed and is permitted to make progress in its execution.
setPriority
public final void setPriority(int newPriority)
First the checkAccess method of this thread is called
with no arguments. This may result in throwing a
SecurityException.
Otherwise, the priority of this thread is set to the smaller of
the specified newPriority and the maximum permitted
priority of the thread's thread group.
MIN_PRIORITY to
MAX_PRIORITY.
getPriority
public final int getPriority()
setName
public final void setName(String name)
name.
First the checkAccess method of this thread is called
with no arguments. This may result in throwing a
SecurityException.
getName
public final String getName()
getThreadGroup
public final ThreadGroup getThreadGroup()
activeCount
public static int activeCount()
enumerate
public static int enumerate(Thread tarray[])
enumerate method of this thread's thread group with
the array argument.
countStackFrames
public native int countStackFrames()
join
public final synchronized void join(long millis) throws InterruptedException
millis milliseconds for this thread to
die. A timeout of 0 means to wait forever.
join
public final synchronized void join(long millis,
int nanos) throws InterruptedException
millis milliseconds plus
nanos nanoseconds for this thread to die.
join
public final void join() throws InterruptedException
dumpStack
public static void dumpStack()
setDaemon
public final void setDaemon(boolean on)
This method must be called before the thread is started.
true, marks this thread as a
daemon thread.
isDaemon
public final boolean isDaemon()
true if this thread is a daemon thread;
false otherwise.
checkAccess
public void checkAccess()
If there is a security manager, its checkAccess method
is called with this thread as its argument. This may result in
throwing a SecurityException.
toString
public String toString()
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