Previously we have discussed about
Thread Priority
In java each thread is assigned a priority, which affects the order in which it is scheduled for running. Thread priorities are integers that specify the relative priority of one thread to another. As an absolute value, a priority is meaningless; a higher-priority thread doesn’t run any faster than a lower-priority thread if it is the only thread running. Instead, a thread’s priority is used to decide when to switch from one running thread to the next. This is called a context switch.
In case, when threads have same priority are given equal treatment by the java schedular and, therefore they share the processor on a first-come , first-serve basic. Java permits us to set the priority of a thread using setPriority() method as :
ThreadName.setPriority(int number);
The int number is an integer value to which the thread priority is set. The thread class defines several priority constants:
MIN_PRIORITY = 1
NORM_PRIORITY = 5
MAX_PRIORITY = 10
The int number may assume one of these constants or any value between 1 to 10. Note the default priority is NORM_PRIORITY.
When multiple threads are ready for execution , the java system chooses the highest priority thread and execute it.For a thread of lower priority to gain control ,one of the following things should happen:
1) run()
2) sleep()
3) wait()
Example of Thread Priority:
Below Example illustrate the effect of assigning higher priority to a thread.Note that although the thread A started first, the higher priority thread B has preempted it and started printing the output first.Immediately the thread C that has been assigned the highest priority takes control over the other two threads.The Thread A is the last to complete.
class A extends Thread {
public void run(){
System.out.println("** THREAD A STARTED **");
for(int i=0;i<4;i++){
System.out.println("THHREAD A : "+i);
}
System.out.println("Exit From Thread A");
}
}
class B extends Thread {
public void run(){
System.out.println("** THREAD B STARTED **");
for(int i=0;i<4;i++){
System.out.println("THHREAD B : "+i);
}
System.out.println("Exit From Thread B");
}
}
class C extends Thread {
public void run(){
System.out.println("** THREAD C STARTED **");
for(int i=0;i<4;i++){
System.out.println("THHREAD C : "+i);
}
System.out.println("Exit From Thread C");
}
}
public class ThreadPriorityExample {
public static void main(String[] args) {
A a = new A();
B b = new B();
C c = new C();
a.setPriority(Thread.MAX_PRIORITY);
b.setPriority(a.getPriority());
c.setPriority(Thread.MIN_PRIORITY);
System.out.println("--Thread A Strated ");
a.start();
System.out.println("--Thread B Strated ");
b.start();
System.out.println("--Thread C Strated ");
c.start();
System.out.println("--Exit from main Thread--");
}
}
Program Output:
--Thread A Strated
--Thread B Strated
--Thread C Strated
** THREAD A STARTED **
THHREAD A : 0
** THREAD B STARTED **
THHREAD A : 1
THHREAD A : 2
THHREAD A : 3
Exit From Thread A
** THREAD C STARTED **
THHREAD B : 0
THHREAD B : 1
--Exit from main Thread--
THHREAD B : 2
THHREAD B : 3
Exit From Thread B
THHREAD C : 0
THHREAD C : 1
THHREAD C : 2
THHREAD C : 3
Exit From Thread C
Software Developer by Profession with 3.0 Yrs of Experience , through this blog i'am sharing my industrial Java Knowledge to entire world. For any question or query any one can comment below or mail me at pushkar.itsitm52@gmail.com.
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