8. Java concurrency 1. Threads

Август 9, 2022

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8. Java concurrency 1. Threads

Содержание

2. Concurrency A single application is often expected to do more than one thing at a time
3. Processes A process has a self-contained execution environment A process generally has a complete, private set
4. Threads I Threads are sometimes called lightweight processes Both processes and threads provide an execution environment,
5. Threads II Threads share the process's resources, including memory and open files From the application programmer's
6. Defining a Thread An application that creates an instance of Thread must provide the code that
7. Runnable Object The Runnable interface defines a single method, run, meant to contain the code executed
8. Runnable Object Example public class HelloRunnable implements Runnable { public void run() { System.out.println("Hello from a
9. Runnable Object in Java 8 public static void main(String args[]) { Runnable r = () ->
10. Thread Subclass The Thread class itself implements Runnable, though its run method does nothing An application
11. Thread Subclass Example public class HelloThread extends Thread { public void run() { System.out.println("Hello from a
12. Runnable vs Thread Subclass A Runnable object employment is more general, because the Runnable object can
13. Pausing Execution with Sleep Thread.sleep causes the current thread to suspend execution for a specified period
14. Sleep Example public class SleepMessages { public static void main(String args[]) throws InterruptedException { String importantInfo[]
15. Thread Race Example Create two classes: first implements Runnable interface, and second extends Thread class. Method
16. Thread Race Example See 811ThreadRace project for the full text. * InfopulseTraining Center
17. Thread Terminations A thread terminates when: its run method returns, by executing a return statement after
18. Interrupted Status When the interrupt method is called on a thread, the interrupted status of the
19. How to Check Interrupted Status To find out whether the interrupted status was set, first call
20. InterruptedException If a thread is blocked, it cannot check the interrupted status This is where the
21. InterruptedException Example for (int i = 0; i // Pause for 4 seconds try { Thread.sleep(4000);
22. Joins The join method allows one thread to wait for the completion of another If t
23. Join Exercise Modify 811ThreadRace project so that first thread should wait for second thread finishing *
24. ThreadRace Class public static void main(String[] args) throws InterruptedException{ ThreadRunnab r = new ThreadRunnab(); Thread t1
25. Join Exercise See 812ThreadJoin project for the full text. * InfopulseTraining Center
26. Thread Priority public final void setPriority(int newPriority) - changes the priority of this thread public final
27. Sharing Resources Example Try to generate Fibonacci series in one thread and print its values in
28. Sharing Resources Example See 813Resources project for the full text. * InfopulseTraining Center
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Concurrency
A single application is often expected to do more than one

thing at a time
Software that can do such things is known as concurrent software
Since version 5.0, the Java platform has also included high-level concurrency APIs

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Processes
A process has a self-contained execution environment
A process generally has a

complete, private set of basic run-time resources (e.g own memory space)
A Java application can create additional processes using a ProcessBuilder object.
Multiprocess applications are beyond the scope of this lesson

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Threads I
Threads are sometimes called lightweight processes
Both processes and threads provide

an execution environment, but creating a new thread requires fewer resources than creating a new process.
Threads exist within a process — every process has at least one thread

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Threads II
Threads share the process's resources, including memory and open files
From

the application programmer's point of view, you start with just one thread, called the main thread
This thread has the ability to create additional threads

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Слайд 6

Defining a Thread
An application that creates an instance of Thread must

provide the code that will run in that thread:
Provide a Runnable object.
Create Thread Subclass.

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Runnable Object
The Runnable interface defines a single method, run, meant to

contain the code executed in the thread
The Runnable object is passed to the Thread constructor
Thread’s start method is called

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Слайд 8

Runnable Object Example
public class HelloRunnable implements Runnable {
public void run()

{
System.out.println("Hello from a thread!");
}
public static void main(String args[]) {
(new Thread(new HelloRunnable())).start();
}
}

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Слайд 9

Runnable Object in Java 8
public static void main(String args[]) {
Runnable

r =
() -> System.out.println("Hello world!");
new Thread(r).start();
}

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Thread Subclass
The Thread class itself implements Runnable, though its run method

does nothing
An application can subclass Thread, providing its own implementation of run

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Thread Subclass Example
public class HelloThread extends Thread {
public void run()

{ System.out.println("Hello from a thread!");
}
public static void main(String args[]) { (new HelloThread()).start();
}
}

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Слайд 12

Runnable vs Thread Subclass
A Runnable object employment is more general, because

the Runnable object can subclass a class other than Thread
Thread subclassing is easier to use in simple applications, but is limited by the fact that your task class must be a descendant of Thread
A Runnable object is applicable to the high-level thread management APIs

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Слайд 13

Pausing Execution with Sleep
Thread.sleep causes the current thread to suspend execution

for a specified period
This is an efficient means of making processor time available to the other threads of an application or other applications that might be running on a computer system
The sleep period can be terminated by interrupts

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Слайд 14

Sleep Example
public class SleepMessages {
public static void main(String args[]) throws

InterruptedException {
String importantInfo[] = { "Mares eat oats",
"Does eat oats", "Little lambs eat ivy",
"A kid will eat ivy too"};
for (int i = 0; i < importantInfo.length; i++) {
Thread.sleep(4000);
System.out.println(importantInfo[i]);
}
}
}

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Слайд 15

Thread Race Example
Create two classes: first implements Runnable interface, and second

extends Thread class. Method run() in both classes prints thread and iteration numbers and sleeps in some seconds.

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Слайд 16

Thread Race Example
See 811ThreadRace project for the full text.
*
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Слайд 17

Thread Terminations
A thread terminates when:
its run method returns, by executing a

return statement
after executing the last statement in the method body
if an exception occurs that is not caught in the method
The interrupt method can be used to request termination of a thread

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Слайд 18

Interrupted Status
When the interrupt method is called on a thread, the

interrupted status of the thread is set
This is a boolean flag that is present in every thread
Each thread should occasionally check whether it has been interrupted

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Слайд 19

How to Check Interrupted Status
To find out whether the interrupted status

was set, first call the static Thread.currentThread method to get the current thread and then call the isInterrupted method:
while (!Thread.currentThread().isInterrupted())
{
do more work
}

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Слайд 20

InterruptedException
If a thread is blocked, it cannot check the interrupted status
This

is where the InterruptedException comes in
When the interrupt method is called on a thread that blocks on a call such as sleep or wait, the blocking call is terminated by an InterruptedException

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Слайд 21

InterruptedException Example
for (int i = 0; i < importantInfo.length; i++)

{
// Pause for 4 seconds
try { Thread.sleep(4000); }
catch (InterruptedException e) {
return;
}
System.out.println(importantInfo[i]);
}

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Слайд 22

Joins
The join method allows one thread to wait for the completion

of another
If t is a Thread object whose thread is currently executing, t.join() causes the current thread to pause execution until t's thread terminates
Overloads of join allow the programmer to specify a waiting period
join responds to an interrupt by exiting with an InterruptedException

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Слайд 23

Join Exercise
Modify 811ThreadRace project so that first thread should wait for

second thread finishing

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Слайд 24

ThreadRace Class
public static void main(String[] args) throws InterruptedException{
ThreadRunnab r = new

ThreadRunnab();
Thread t1 = new Thread(r);
Thread t2 = new ThreadThread();
r.setThread(t2);
t1.start();
t2.start();
}

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Слайд 25

Join Exercise
See 812ThreadJoin project for the full text.
*
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Слайд 26

Thread Priority
public final void setPriority(int newPriority) - changes the priority of this thread
public final int getPriority()

- returns this thread's priority

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Слайд 27

Sharing Resources Example
Try to generate Fibonacci series in one thread and

print its values in another thread

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Слайд 28

8. Java concurrency 1. Threads

Содержание

ConcurrencyA single application is often expected to do more than one

ProcessesA process has a self-contained execution environmentA process generally has a

Threads IThreads are sometimes called lightweight processesBoth processes and threads provide

Threads IIThreads share the process's resources, including memory and open filesFrom

Defining a ThreadAn application that creates an instance of Thread must

Runnable ObjectThe Runnable interface defines a single method, run, meant to

Runnable Object Examplepublic class HelloRunnable implements Runnable { public void run()

Runnable Object in Java 8public static void main(String args[]) { Runnable

Thread SubclassThe Thread class itself implements Runnable, though its run method

Thread Subclass Examplepublic class HelloThread extends Thread { public void run()

Runnable vs Thread SubclassA Runnable object employment is more general, because

Pausing Execution with SleepThread.sleep causes the current thread to suspend execution

Sleep Examplepublic class SleepMessages { public static void main(String args[]) throws

Thread Race ExampleCreate two classes: first implements Runnable interface, and second

Thread Race ExampleSee 811ThreadRace project for the full text.*InfopulseTraining Center

Thread TerminationsA thread terminates when:its run method returns, by executing a

Interrupted StatusWhen the interrupt method is called on a thread, the

How to Check Interrupted StatusTo find out whether the interrupted status

InterruptedExceptionIf a thread is blocked, it cannot check the interrupted statusThis

InterruptedException Examplefor (int i = 0; i < importantInfo.length; i++)

JoinsThe join method allows one thread to wait for the completion

Join ExerciseModify 811ThreadRace project so that first thread should wait for

ThreadRace Classpublic static void main(String[] args) throws InterruptedException{ ThreadRunnab r = new

Join ExerciseSee 812ThreadJoin project for the full text.*InfopulseTraining Center

Thread Prioritypublic final void setPriority(int newPriority) - changes the priority of this threadpublic final int getPriority()

Sharing Resources ExampleTry to generate Fibonacci series in one thread and

Sharing Resources ExampleSee 813Resources project for the full text.*InfopulseTraining Center

Похожие презентации

Concurrency
A single application is often expected to do more than one

Processes
A process has a self-contained execution environment
A process generally has a

Threads I
Threads are sometimes called lightweight processes
Both processes and threads provide

Threads II
Threads share the process's resources, including memory and open files
From

Defining a Thread
An application that creates an instance of Thread must

Runnable Object
The Runnable interface defines a single method, run, meant to

Runnable Object Example
public class HelloRunnable implements Runnable {
public void run()

Runnable Object in Java 8
public static void main(String args[]) {
Runnable

Thread Subclass
The Thread class itself implements Runnable, though its run method

Thread Subclass Example
public class HelloThread extends Thread {
public void run()

Runnable vs Thread Subclass
A Runnable object employment is more general, because

Pausing Execution with Sleep
Thread.sleep causes the current thread to suspend execution

Sleep Example
public class SleepMessages {
public static void main(String args[]) throws

Thread Race Example
Create two classes: first implements Runnable interface, and second

Thread Race Example
See 811ThreadRace project for the full text.
*
InfopulseTraining Center

Thread Terminations
A thread terminates when:
its run method returns, by executing a

Interrupted Status
When the interrupt method is called on a thread, the

How to Check Interrupted Status
To find out whether the interrupted status

InterruptedException
If a thread is blocked, it cannot check the interrupted status
This

InterruptedException Example
for (int i = 0; i < importantInfo.length; i++)

Joins
The join method allows one thread to wait for the completion

Join Exercise
Modify 811ThreadRace project so that first thread should wait for

ThreadRace Class
public static void main(String[] args) throws InterruptedException{
ThreadRunnab r = new

Join Exercise
See 812ThreadJoin project for the full text.
*
InfopulseTraining Center

Thread Priority
public final void setPriority(int newPriority) - changes the priority of this thread
public final int getPriority()

Sharing Resources Example
Try to generate Fibonacci series in one thread and

Sharing Resources Example
See 813Resources project for the full text.
*
InfopulseTraining Center