Thread (Java(TM) ME Connected Limited Device Configuration, Version 8 (JSR360 Final Release))

java.lang.Object
- java.lang.Thread

All Implemented Interfaces:

Runnable
```
public class Thread
extends Object
implements Runnable
```
A thread is a thread of execution in a program. The Java Virtual Machine allows an application to have multiple threads of execution running concurrently.
Every thread has a priority. Threads with higher priority are executed in preference to threads with lower priority. 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.
When a Java Virtual Machine starts up, there is usually a single 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:
- The exit method of class Runtime has been called and the security manager has permitted the exit operation to take place.
- All threads have died, either by returning from the call to the run method or by throwing an exception that propagates beyond the run 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.
Unless otherwise noted, passing a null argument to a constructor or method in this class will cause a NullPointerException to be thrown.
Since:

JDK1.0, CLDC 1.0

See Also:
Runnable, Runtime.exit(int), run()

Field Summary

Fields
Modifier and Type	Field and Description
`static int`	`MAX_PRIORITY` The maximum priority that a thread can have.
`static int`	`MIN_PRIORITY` The minimum priority that a thread can have.
`static int`	`NORM_PRIORITY` The default priority that is assigned to a thread.

Constructor Summary

Constructors
Constructor and Description
`Thread()` Allocates a new `Thread` object.
`Thread(Runnable target)` Allocates a new `Thread` object.
`Thread(Runnable target, String name)` Allocates a new `Thread` object so that it has `target` as its run object and has the specified `name` as its name.
`Thread(String name)` Allocates a new `Thread` object.

Method Summary

Methods
Modifier and Type	Method and Description
`static int`	`activeCount()` Returns the number of active threads.
`void`	`checkAccess()` Determines if the currently running thread has permission to modify this thread.
`static Thread`	`currentThread()` Returns a reference to the currently executing thread object.
`long`	`getId()` Returns the identifier of this Thread.
`String`	`getName()` Returns this thread's name.
`int`	`getPriority()` Returns this thread's priority.
`static boolean`	`holdsLock(Object obj)` Returns `true` if and only if the current thread holds the monitor lock on the specified object.
`void`	`interrupt()` Interrupts this thread.
`static boolean`	`interrupted()` Tests whether the current thread has been interrupted.
`boolean`	`isAlive()` Tests if this thread is alive.
`boolean`	`isInterrupted()` Tests whether this thread has been interrupted.
`void`	`join()` Waits for this thread to die.
`void`	`join(long millis)` Waits at most `millis` milliseconds for this thread to die.
`void`	`join(long millis, int nanos)` Waits at most `millis` milliseconds plus `nanos` nanoseconds for this thread to die.
`void`	`run()` If this thread was constructed using a separate `Runnable` run object, then that `Runnable` object's `run` method is called; otherwise, this method does nothing and returns.
`void`	`setName(String name)` Changes the name of this thread to be equal to the argument `name`.
`void`	`setPriority(int newPriority)` Changes the priority of this thread.
`static void`	`sleep(long millis)` Causes the currently executing thread to sleep (temporarily cease execution) for the specified number of milliseconds, subject to the precision and accuracy of system timers and schedulers.
`static void`	`sleep(long millis, int nanos)` Causes the currently executing thread to sleep (temporarily cease execution) for the specified number of milliseconds plus the specified number of nanoseconds, subject to the precision and accuracy of system timers and schedulers.
`void`	`start()` Causes this thread to begin execution; the Java Virtual Machine calls the `run` method of this thread.
`String`	`toString()` Returns a string representation of this thread, including the thread's name and priority.
`static void`	`yield()` A hint to the scheduler that the current thread is willing to yield its current use of a processor.

Methods inherited from class java.lang.Object
clone, equals, getClass, hashCode, notify, notifyAll, wait, wait, wait

- Field Detail
  - MAX_PRIORITY
```
public static final int MAX_PRIORITY
```
    The maximum priority that a thread can have.
    
    See Also:
    Constant Field Values
  - MIN_PRIORITY
```
public static final int MIN_PRIORITY
```
    The minimum priority that a thread can have.
    
    See Also:
    Constant Field Values
  - NORM_PRIORITY
```
public static final int NORM_PRIORITY
```
    The default priority that is assigned to a thread.
    
    See Also:
    Constant Field Values
- Constructor Detail
  - Thread
```
public Thread()
```
    Allocates a new Thread object. This constructor has the same effect as Thread (null, gname), where gname is a newly generated name. Automatically generated names are of the form "Thread-"+n, where n is an integer.
  - Thread
```
public Thread(Runnable target)
```
    Allocates a new Thread object. This constructor has the same effect as Thread (target, gname), where gname is a newly generated name. Automatically generated names are of the form "Thread-"+n, where n is an integer.
    
    Parameters:
    target - the object whose run method is invoked when this thread is started. If null, this classes run method does nothing.
  - Thread
```
public Thread(Runnable target,
      String name)
```
    Allocates a new Thread object so that it has target as its run object and has the specified name as its name.
    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.
    
    Parameters:
    target - the object whose run method is invoked when this thread is started. If null, this thread's run method is invoked.
    name - the name of the new thread
  - Thread
```
public Thread(String name)
```
    Allocates a new Thread object. This constructor has the same effect as Thread (null, name).
    
    Parameters:
    name - the name of the new thread
- Method Detail
  - activeCount
```
public static int activeCount()
```
    Returns the number of active threads.
    
    Returns:
    the number of active threads in the virtual machine.
  - checkAccess
```
public final void checkAccess()
```
    Determines if the currently running thread has permission to modify this thread.
    If there is a security manager, its checkAccess method is called with this thread as its argument. This may result in throwing a SecurityException.
    
    Throws:
    
    SecurityException - if the current thread is not allowed to access this thread.
    See Also:
    SecurityManager.checkAccess(Thread)
  - currentThread
```
public static Thread currentThread()
```
    Returns a reference to the currently executing thread object.
    
    Returns:
    the currently executing thread.
  - getId
```
public long getId()
```
    Returns the identifier of this Thread. The thread ID is a positive long number generated when this thread was created. The thread ID is unique and remains unchanged during its lifetime. When a thread is terminated, this thread ID may be reused.
    
    Returns:
    this thread's ID.
    Since:
    
    1.5
  - getName
```
public final String getName()
```
    Returns this thread's name.
    
    Returns:
    this thread's name.
    See Also:
    setName(String)
  - getPriority
```
public final int getPriority()
```
    Returns this thread's priority.
    
    Returns:
    this thread's priority.
    See Also:
    setPriority(int)
  - holdsLock
```
public static boolean holdsLock(Object obj)
```
    Returns true if and only if the current thread holds the monitor lock on the specified object.
    This method is designed to allow a program to assert that the current thread already holds a specified lock:
```
     assert Thread.holdsLock(obj);
 
```
    Parameters:
    obj - the object on which to test lock ownership
    
    Returns:
    true if the current thread holds the monitor lock on the specified object.
    
    Throws:
    
    NullPointerException - if obj is null
    Since:
    
    1.4
  - interrupt
```
public void interrupt()
```
    Interrupts this thread.
    Unless the current thread is interrupting itself, which is always permitted, the checkAccess method of this thread is invoked, which may cause a SecurityException to be thrown.
    If this thread is blocked in an invocation of the wait(), wait(long), or wait(long, int) methods of the Object class, or of the join(), join(long), join(long, int), sleep(long), or sleep(long, int), methods of this class, then its interrupt status will be cleared and it will receive an InterruptedException.
    If none of the previous conditions hold then this thread's interrupt status will be set.
    
    Interrupting a thread that is not alive need not have any effect.
    In an implementation conforming to the CLDC Specification, this operation is not required to cancel or clean up any pending I/O operations that the thread may be waiting for.
    
    Throws:
    
    SecurityException - if the current thread cannot modify this thread
  - interrupted
```
public static boolean interrupted()
```
    Tests whether the current thread has been interrupted. The interrupted status of the thread is cleared by this method. In other words, if this method were to be called twice in succession, the second call would return false (unless the current thread were interrupted again, after the first call had cleared its interrupted status and before the second call had examined it).
    A thread interruption ignored because a thread was not alive at the time of the interrupt will be reflected by this method returning false.
    
    Returns:
    true if the current thread has been interrupted; false otherwise.
    See Also:
    isInterrupted()
  - isAlive
```
public final boolean isAlive()
```
    Tests if this thread is alive. A thread is alive if it has been started and has not yet died.
    
    Returns:
    true if this thread is alive; false otherwise.
  - isInterrupted
```
public boolean isInterrupted()
```
    Tests whether this thread has been interrupted. The interrupted status of the thread is unaffected by this method.
    A thread interruption ignored because a thread was not alive at the time of the interrupt will be reflected by this method returning false.
    
    Returns:
    true if this thread has been interrupted; false otherwise.
    See Also:
    interrupted()
  - join
```
public final void join()
                throws InterruptedException
```
    Waits for this thread to die.
    An invocation of this method behaves in exactly the same way as the invocation
    join(0)
    
    Throws:
    
    InterruptedException - if any thread has interrupted the current thread. The interrupted status of the current thread is cleared when this exception is thrown.
  - join
```
public final void join(long millis)
                throws InterruptedException
```
    Waits at most millis milliseconds for this thread to die. A timeout of 0 means to wait forever.
    
    Parameters:
    millis - the time to wait in milliseconds
    
    Throws:
    
    IllegalArgumentException - if the value of millis is negative
    
    InterruptedException - if any thread has interrupted the current thread. The interrupted status of the current thread is cleared when this exception is thrown.
  - join
```
public final void join(long millis,
        int nanos)
                throws InterruptedException
```
    Waits at most millis milliseconds plus nanos nanoseconds for this thread to die.
    
    Parameters:
    millis - the time to wait in milliseconds
    nanos - 0-999999 additional nanoseconds to wait
    
    Throws:
    
    IllegalArgumentException - if the value of millis is negative, or the value of nanos is not in the range 0-999999
    
    InterruptedException - if any thread has interrupted the current thread. The interrupted status of the current thread is cleared when this exception is thrown.
  - run
```
public void run()
```
    If this thread was constructed using a separate 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.
    
    Specified by:
    
    run in interface Runnable
    
    See Also:
    start()
  - setName
```
public final void setName(String name)
```
    Changes the name of this thread to be equal to the argument name.
    First the checkAccess method of this thread is called with no arguments. This may result in throwing a SecurityException.
    
    Parameters:
    name - the new name for this thread.
    
    Throws:
    
    SecurityException - if the current thread cannot modify this thread.
    See Also:
    getName(), checkAccess()
  - setPriority
```
public final void setPriority(int newPriority)
```
    Changes the priority of this thread.
    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 for the thread..
    
    Parameters:
    newPriority - priority to set this thread to
    
    Throws:
    
    IllegalArgumentException - If the priority is not in the range MIN_PRIORITY to MAX_PRIORITY.
    
    SecurityException - if the current thread cannot modify this thread.
    See Also:
    getPriority(), checkAccess(), MAX_PRIORITY, MIN_PRIORITY
  - sleep
```
public static void sleep(long millis)
                  throws InterruptedException
```
    Causes the currently executing thread to sleep (temporarily cease execution) for the specified number of milliseconds, subject to the precision and accuracy of system timers and schedulers. The thread does not lose ownership of any monitors.
    
    Parameters:
    millis - the length of time to sleep in milliseconds
    
    Throws:
    
    IllegalArgumentException - if the value of millis is negative
    
    InterruptedException - if any thread has interrupted the current thread. The interrupted status of the current thread is cleared when this exception is thrown.
  - sleep
```
public static void sleep(long millis,
         int nanos)
                  throws InterruptedException
```
    Causes the currently executing thread to sleep (temporarily cease execution) for the specified number of milliseconds plus the specified number of nanoseconds, subject to the precision and accuracy of system timers and schedulers. The thread does not lose ownership of any monitors.
    
    Parameters:
    millis - the length of time to sleep in milliseconds
    nanos - 0-999999 additional nanoseconds to sleep
    
    Throws:
    
    IllegalArgumentException - if the value of millis is negative, or the value of nanos is not in the range 0-999999
    
    InterruptedException - if any thread has interrupted the current thread. The interrupted status of the current thread is cleared when this exception is thrown.
  - start
```
public void start()
```
    Causes this thread to begin execution; the Java Virtual Machine calls the 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).
    It is never legal to start a thread more than once. In particular, a thread may not be restarted once it has completed execution.
    
    Throws:
    
    IllegalThreadStateException - if the thread was already started.
    See Also:
    run()
  - toString
```
public String toString()
```
    Returns a string representation of this thread, including the thread's name and priority.
    
    Overrides:
    
    toString in class Object
    
    Returns:
    a string representation of this thread.
  - yield
```
public static void yield()
```
    A hint to the scheduler that the current thread is willing to yield its current use of a processor. The scheduler is free to ignore this hint.
    Yield is a heuristic attempt to improve relative progression between threads that would otherwise over-utilise a CPU. Its use should be combined with detailed profiling and benchmarking to ensure that it actually has the desired effect.
    It is rarely appropriate to use this method. It may be useful for debugging or testing purposes, where it may help to reproduce bugs due to race conditions. It may also be useful when designing concurrency control constructs.

Class Thread

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

MAX_PRIORITY

MIN_PRIORITY

NORM_PRIORITY

Constructor Detail

Thread

Thread

Thread

Thread

Method Detail

activeCount

checkAccess

currentThread

getId

getName

getPriority

holdsLock

interrupt

interrupted

isAlive

isInterrupted

join

join

join

run

setName

setPriority

sleep

sleep

start

toString

yield