Java Certification Question 0086

What will happen when you attempt to compile and run the following code

public class MySwitch{

public static void main(String argv[]){
MySwitch ms= new MySwitch();
ms.amethod();
}

public void amethod(){
int k=10;
switch(k){
default: //Put the default at the bottom, not here
System.out.println("This is the default output");
break;
case 10:
System.out.println("ten");
case 20:
System.out.println("twenty");
break;
}
}
}

1) None of these options
2) Compile time error target of switch must be an integral type
3) Compile and run with output "This is the default output"
4) Compile and run with output of the single line "ten"

Answer)

1) None of these options

Because of the lack of a break statement after the break 10; statement the actual output will be

"ten" followed by "twenty"

Java Certification Question 0085

What will happen when you attempt to compile and run the following code

public class Hope{

public static void main(String argv[]){
Hope h = new Hope();
}

protected Hope(){
for(int i =0; i <10; i++ )
System.out.println(i);
}
}
}

1) Compilation error: Constructors cannot be declared protected
2) Run time error: Constructors cannot be declared protected
3) Compilation and running with output 0 to 10
4) Compilation and running with output 0 to 9

Answer)

4) Compilation and running with output 0 to 9

Java Certification Question 0084

Under what circumstances might you use the yield method of the Thread class

1) To call from the currently running thread to allow another thread of the same or higher priority to run
2) To call on a waiting thread to allow it to run
3) To allow a thread of higher priority to run
4) To call from the currently running thread with a parameter designating which thread should be allowed to run

Answer)

1) To call from the currently running thread to allow another thread of the same or higher priority to run

Option 3 looks plausible but there is no guarantee that the thread that grabs the cpu time will be of a higher priority. It will depend on the threading algorithm of the Java Virtual Machine and the underlying operating system

Java Certification Question 0083

For a class defined inside a method, what rule governs access to the variables of the enclosing method?

1) The class can access any variable
2) The class can only access static variables
3) The class can only access transient variables
4) The class can only access final variables

Answer)

4) The class can only access final variables

Java Certification Question 0082

What can cause a thread to stop executing?

1) The program exits via a call to System.exit(0);
2) Another thread is given a higher priority
3) A call to the thread's stop method.
4) A call to the halt method of the Thread class

Answer)

1) The program exits via a call to exit(0);
2) The priority of another thread is increased
3) A call to the stop method of the Thread class

Java threads are somewhat platform dependent and you should be carefull when making assumptions about Thread priorities. On some platforms you may find that a Thread with higher priorities gets to "hog" the processor.