Strange problem with simple multithreading program in Java
- by Elizabeth
Hello, I am just starting play with multithreading programming. I would like to my program show alternately character '-' and '+' but it doesn't. My task is to use synchronized keyword. As far I have:
class FunnyStringGenerator{
private char c;
public FunnyStringGenerator(){
c = '-';
}
public synchronized char next(){
if(c == '-'){
c = '+';
}
else{
c = '-';
}
return c;
}
}
class ThreadToGenerateStr implements Runnable{
FunnyStringGenerator gen;
public ThreadToGenerateStr(FunnyStringGenerator fsg){
gen = fsg;
}
@Override
public void run() {
for(int i = 0; i < 10; i++){
System.out.print(gen.next());
}
}
}
public class Main{
public static void main(String[] args) throws IOException {
FunnyStringGenerator FSG = new FunnyStringGenerator();
ExecutorService exec = Executors.newCachedThreadPool();
for(int i = 0; i < 20; i++){
exec.execute(new ThreadToGenerateStr(FSG));
}
}
}
EDIT: I also testing Thread.sleep in run method instead for loop.
