java programming language_8_multithread concurrency

8/11/2019 Java Programming Language_8_Multithread Concurrency

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NGN NG LP TRNHJAVA

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MULTITHREADS &

CONCURRENCY

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Nidung

1. Giithiu

2. Tothreads

3. Unresponsive User Interface

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1. Giithiuvalung

nlung(single thread) :Mtimvo (entry point) : main() method

Mtimra (exit point)

alung(multi threads):Mtimvo ban u(main() method)

Theo sau binhiuimvo, imra chysong song vimain()

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1.1anhim(multi-tasking)Hthnganhim

Vd: Hiuhnh Windows,Unix Thchinnhiutc vngthibngcch chia sti nguyn : CPU,

bnh, cc knh vo ra (I/O channels) Single-CPU machine : mttc vtimtthiim Multi-CPU machine: nhiutc vc ththchintimtthiim

Mcch: Gip tiuho vicsdngti nguyn

Phnloi Co-operative multitasking systems:

Mitc vphitnguynaliquyniukhincho tc vkhc Stin cy/tin tnggiacc tc v Mttc vkhng hptc c thtreo hthng

Pre-emptive multitasking systems: Cc tc vchytrong mtkhung thigian xc nh Htkhung thigian, phialiquyniukhincho cc tc vkhc

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1.2alung(multi-threading in aprocess) Khi nimprocess:

/v Unix, Linux: tora mtprocess mi

/v Windows: chymtchngtrnh

cimcaprocess: C khng gian achring

C khiiukhinring

Sdngnhiuti nguyn hthng=> heavyweight

Trong mtprocess, c thchynhiuthreads cithinhiu

nnghthng

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1.2alung

cimcathread L mtlightweight process

Chybn trong mtprocess

Cc threads chia s

cng mtkhng gian ach,

Cng mttpcc ti nguyn cphn phi

V mi trngcaprocess

Phitqunl ti nguyn bn trong mtprocess : Stack, registers, program counter

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1.2alung

Lich cavicsdngmultithreading trong mtchngtrnh

tnghiusut= tiuvicsdngti nguyn Vd: mtthread angbblock (chmtthao tc I/O ktthc), thread

khc c thsdngCPU thchinvictnh ton => hiunngvthng lngcachngtrnh stthn

mbostngtc tthnvingidng Vd: trong mtngdngword, trong khi mtthread angin hoclutr

file, mtthread khc c thcsdngtiptcsontho

Trong ngdngGUI, multit-threading mbocung cpmtresponsive user interface

ngdngSwing datrn multi-threading => c thsdngminhhochh/ camulti-threading

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1.3 Java profiling

Java profiling l g? Application Developer:Monitor, profile, take thread dumps,

browse heap dumps

System Administrator:Monitor and control Java applicationsacross the entire network

Java Application User:Create bug reports containing all thenecessary information

Phnmm: YOURKIT

http://www.yourkit.com/ Commercial tool

VisualVM

http://visualvm.java.net/

free

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http://www.yourkit.com/http://visualvm.java.net/http://visualvm.java.net/http://visualvm.java.net/http://www.yourkit.com/http://www.yourkit.com/http://www.yourkit.com/


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VisualVM

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VisualVM

Ci t Visual VM:

https://java.net/projects/visualvm/downloads/download/release137/visualvm_137.zip

Eclipse plugin:http://java.net/projects/visualvm/downloads/download/release133/visualvm_lau

ncher_u1_eclipse_36.zip Unzip the archive into directory of your choice

Add local update site pointing to the chosen directory

Install VisualVM Launcher Feature

Cuhnh Go to Run/Debug-Launching-VisualVM Configurationpreferences :

JDK Home to be used by VisualVM (needs to be a JDK, not JRE) The path to VisualVM executable (VisualVM 1.1+ is supported)

Sdng Create a new application configuration

Choose the "VisualVM Launcher"as the application launcher

Run/Debug the application with the created configuration to have VisualVMstarted automatically

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https://java.net/projects/visualvm/downloads/download/release137/visualvm_137.ziphttps://java.net/projects/visualvm/downloads/download/release137/visualvm_137.ziphttp://java.net/projects/visualvm/downloads/download/release133/visualvm_launcher_u1_eclipse_36.ziphttp://java.net/projects/visualvm/downloads/download/release133/visualvm_launcher_u1_eclipse_36.ziphttp://visualvm.java.net/images/eclipse/preferences.pnghttp://visualvm.java.net/images/eclipse/configuration.pnghttp://visualvm.java.net/images/eclipse/launcher.pnghttp://visualvm.java.net/images/eclipse/launcher.pnghttp://visualvm.java.net/images/eclipse/configuration.pnghttp://visualvm.java.net/images/eclipse/preferences.pnghttp://java.net/projects/visualvm/downloads/download/release133/visualvm_launcher_u1_eclipse_36.ziphttp://java.net/projects/visualvm/downloads/download/release133/visualvm_launcher_u1_eclipse_36.ziphttp://java.net/projects/visualvm/downloads/download/release133/visualvm_launcher_u1_eclipse_36.ziphttp://java.net/projects/visualvm/downloads/download/release133/visualvm_launcher_u1_eclipse_36.ziphttps://java.net/projects/visualvm/downloads/download/release137/visualvm_137.ziphttps://java.net/projects/visualvm/downloads/download/release137/visualvm_137.ziphttps://java.net/projects/visualvm/downloads/download/release137/visualvm_137.zip


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2. Threads

Class threads

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2. Threads

Cch tothreads:

Extend a subclass from the super class Thread and

override the run() method to specify the running behavior

of the thread.

Create an instance and invoke the start() method, which

will call-back the run() on a new thread.

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VD

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3. Unresponsive User Interface

UUI cm tbimtngdngSWING vimtvnglpm

C 2 buttons: Start Counting v Stop Counting

2 handlers ca2 buttons giao tipthng qua mtbinboolean stop The stop-button handler sets the stop flag;

while the start-button handler checks if stop flag has been set

before continuing the next count.

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Vd1: UnresponsiveUI (1/2)

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Vd1: UnresponsiveUI (2/2)

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Tracing the threads

1. The main() method starts in the "main" thread.

2. A new thread "AWT-Windows" (Daemon thread) is startedwhen we step-into the constructor "new UnresponsiveUI()"(because of the "extends JFrame").

3. After executing "setVisible(true)", another two threads arecreated - "AWT-Shutdown" and "AWT-EventQueue-0" (i.e.,the EDT).

4. The "main" thread exits after the main() method completes. Anew thread called "DestroyJavaVM" is created.

5. At this point, there are 4 threads running - "AWT-Windows","AWT-Shutdown" and "AWT-EventQueue-0 (EDT)" and"DestroyJavaVM".

6. Clicking the START button invokes the actionPerformed() inthe EDT.

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Vd2: UnresponsiveUI with Thread

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Tracing the threads

When the "START" button is clicked, a new thread called

"Thread-n" (n is a running number) is created to run the

compute-intensive counting-loop.

However, this thread is not programmed to yield control to

other threads, in particular, the event-dispatching thread.

This program is, however, slightly better than the previousprogram.

The display is updated, and the clicking of "STOP" button

has its effect after some delays.

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Vd3: Unresponsive UI with sleep

Let's modify the program by making a call to the counting-

thread's sleep()method,

which requests the counting-thread to yield control to the

event-dispatching thread to update the display and

response to the "STOP" button.

The counting program now works as desired.

The sleep() method also provides the necessary delay

needed.

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java programming language_8_multithread concurrency

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