Code on Threads

[Pallavi Chakraborty]

Hello everybody,
Here is a code on Thread. I am getting an error during compilation saying - C:\Pallavi's\Javah\JCreator LE\MyProjects\Test1\Ex5.7\ThreadThread.java:23: cannot resolve symbol
symbol : constructor ThreadThread (java.lang.String)
location: class ThreadThread
ThreadThread counterA = new ThreadThread("Counter A");
The code is:

public class ThreadThread extends Thread {
private int currentvalue;
public void Counter(String threadname)
{
currentvalue  = 0;
System.out.print("this is" + this);
start();
}

public void run(){
try {
while(currentvalue < 5) {
System.out.println("*");
Thread.sleep(500);
}}
catch(InterruptedException ie)
{
System.out.print(getName() + "interrupted");

}}
public static void main(String args[])
{
ThreadThread counterA = new ThreadThread("Counter A");
System.out.print("Exit from main");
}
}

Please help me out .
Pallavi
[ March 30, 2003: Message edited by: Pallavi Chakraborty ]

[Reshma Shanbhag]

Hi Pallavi
ThreadThread.java u have mentioned does not have a constructor which takes 'String' as argument. 'Thread' class in java.lang package has a constructor that takes string argument, but constructor's are not inherited.
I have modified your code, and it compiles fine.. i have added in you code a constructor that takes an string argument and calls the super class constructor.

public class ThreadThread extends Thread {
    private int currentvalue;
    
    public ThreadThread(String s){
super(s);
    }
    public void Counter(String threadname){
currentvalue  = 0;
System.out.print("this is" + this);
start();                
    }
    
    public void run(){
        try {
  while(currentvalue < 5) {
    System.out.println("*");
    Thread.sleep(500);
  }
}catch(InterruptedException ie){
    System.out.print(getName() + "interrupted");
    
}
    }
    
    public static void main(String args[]){
ThreadThread counterA = new ThreadThread("Counter A");
System.out.print("Exit from main");
    }
}

Hope this helps you
Reshma

[Pallavi Chakraborty]

Hello Reshma,
Thanks for your reply.
I do have a question. Is this required only for classes which extend Thread.
I coded something similar for a class implementing Runnable but didn't have to specify the construcor.
Here is the code :

public class ThreadStuff implements Runnable {
public int OurArray[] = new int[5];
public int position;

 public synchronized void putvalue(int i, int j) {
 OurArray[i] = j;
System.out.println("The value put in is" + OurArray[i]);
}

 public synchronized void getvalue(int k) {
System.out.print("The value we are getting is" + OurArray[k]);
}

public void run(){
int o =10;
for(int p = 0; p < 5; p++)
{
try
{
Thread.sleep(1000);
System.out.print(Thread.currentThread().getName() + "is  sleeping" );
}
catch(InterruptedException e)
{
}
putvalue(p,o);
getvalue(p);
o = o + 10;
}
}

public static void main(String args[]) {

ThreadStuff ts1 = new ThreadStuff();
Thread t1  = new Thread(ts1);
t1.start();
}

}

Thanks for your help.
Pallavi

[Karthik Veeramani]

Pallavi,
This is not something specific to Thread class, but just an inheritance property. If you define a constructor urself, you must make sure that u invoke the appropriate version of the super class using super keyword. Runnable is just an interface, so theres no problem of super class constructor.
Thanks
Karthik.

[Reshma Shanbhag]

Pallavi,
In this case you are invoking a default constructor of the ThreadStuff class. when u donot specify any explicit constructor, the compiler adds a 0 argument constructor which will implicitly call the 0 argument constructor of the super class (in this case it is java.lang.Object class). This is same for all classes which donot provide a default constructor.
reshma
[ March 31, 2003: Message edited by: Reshma Pai ]

[Pallavi Chakraborty]

Hey Reshma & Karthik,
Thanks for bringing me on track. I was thinking
so narrowly about threads that I was even missing the BASIC things ..
Thanks again.
Pallavi