Question
class Test116
{
static final StringBuffer sb1 = new StringBuffer();
static final StringBuffer sb2 = new StringBuffer();
public static void main(String args[])
{
new Thread()
{
public void run()
{
synchronized(sb1)
{
sb1.append("A");
sb2.append("B");
}
}
}.start();
new Thread()
{
public void run()
{
synchronized(sb1)
{
sb1.append("C");
sb2.append("D");
}
}
}.start(); /* Line 28 */
System.out.println (sb1 + " " + sb2);
}
}
What will be the output of the program?
class Test116
{
static final StringBuffer sb1 = new StringBuffer();
static final StringBuffer sb2 = new StringBuffer();
public static void main(String args[])
{
new Thread()
{
public void run()
{
synchronized(sb1)
{
sb1.append("A");
sb2.append("B");
}
}
}.start();
new Thread()
{
public void run()
{
synchronized(sb1)
{
sb1.append("C");
sb2.append("D");
}
}
}.start(); /* Line 28 */
System.out.println (sb1 + " " + sb2);
}
}
Answer: Option D
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Can you guarantee the order in which threads are going to run? No you can't. So how do
you know what the output will be? The output cannot be determined.
add this code after line 28:
try { Thread.sleep(5000); } catch(InterruptedException e) { }
and you have some chance of predicting the outcome.
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