Practice Threads Multiple Choice Questions with Answers Quiz-1

Q.1.

What notifyAll() method do?

Wakes up one threads that are waiting on this object's monitor
Wakes up all threads that are not waiting on this object's monitor
Wakes up all threads that are waiting on this object's monitor
None of the above

Explanation

Q.2.

Analyze the following code:

public class Test implements Runnable{
        public static void main(String[] args){
                Test t = new Test();
                t.start();
        }

        public void run() { }
}

The program does not compile because the start() method is not defined in the Test class.
The program compiles, but it does not run because the start() method is not defined.
The program compiles, but it does not run because the run() method is not implemented.
The program compiles and runs fine.

Q.3.

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

1. public class Test extends Thread{
2.       public static void main(String argv[]){
3.             Test t = new Test();
4.             t.run();
5.             t.start();
6.       }
7.       public void run(){
8.             System.out.println("run-test");
9.       }
10. }

run-test run-test
run-test
Compilation fails due to an error on line 4
Compilation fails due to an error on line 7
None of these

Explanation

Q.4.

What will be output of the following program code?

public class Test implements Runnable{
      public void run(){
            System.out.print("go");
      }
    
      public static void main(String arg[]) {
            Thread t = new Thread(new Test());
            t.run();
            t.run();
            t.start();
      }
}

Compilation fails.
An exception is thrown at runtime.
"go" is printed
"gogogo" is printed
"gogo" is printed

Q.5.

Given the code. What will be the result?

public class Test implements Runnable{
      public static void main(String[] args) throws InterruptedException{
            Thread a = new Thread(new Test());
            a.start();
        
            System.out.print("Begin");
            a.join();
            System.out.print("End");
      }
    
      public void run(){
            System.out.print("Run");
      }
}

Compilation fails.
An exception is thrown at runtime.
"BeginRunEnd" is printed.
"BeginEndRun" is printed.
"BeginEnd" is printed.

Q.6.

What is the output for the below code ?

public class Test extends Thread{
      public static void main(String argv[]){
            Test t = new Test();
            t.run();
      }

      public void start(){
            for(int i = 0; i < 10; i++){
                  System.out.println("Value of i = " + i);
            }
      }
}

A compile time error indicating that no run method is defined for the Thread class
A run time error indicating that no run method is defined for the Thread class
Clean compile and at run time the values 0 to 9 are printed out
Clean compile but no output at runtime
None of these

Q.7.

Which keyword when applied on a method indicates that only one thread should execute the method at a time.

volatile
synchronized
native
static
final

Q.8.

What is the output for the below code ?

class A implements Runnable{
      public void run(){
            System.out.println(Thread.currentThread().getName());
      }
}

1. public class Test{		
2.       public static void main(String... args){	
3.             A a = new A();
4.	       Thread t = new Thread(a);
5.	       t.setName("good");
6.	       t.start();
7.       }
8. }

good
null
Compilation fails with an error at line 5
Compilation succeed but Runtime Exception
None of these

Explanation

Q.9.

Predict the output:

public class Test extends Thread{
      private int i;
      public void run(){
            i++;
      }

      public static void main(String[] args){
            Test a = new Test();
            a.run();
            System.out.print(a.i);
            a.start();
            System.out.print(a.i);
      }
}

Prints
Prints
Prints
Compiler error
IllegalThreadStateException is thrown

Explanation

Q.10.

What will be the output after compiling and executing the following code?

public class Test implements Runnable{
      public static void main(String[] args) throws InterruptedException{
            Thread a = new Thread(new Test());
            a.start();
            System.out.print("Begin");
            a.join();
            System.out.print("End");
      }
    
      public void run(){
            System.out.print("Run");
      }
}

Compilation fails.
An exception is thrown at runtime.
"BeginRunEnd" is printed.
"BeginEndRun" is printed.
"BeginEnd" is printed.

Q.11.

Predict the output:

class A implements Runnable{
      public void run(){
            try{
                  for(int i=0;i<4;i++){
                        Thread.sleep(100);
                        System.out.println(Thread.currentThread().getName());
                  }
            }catch(InterruptedException e){
            }
      }
}

public class Test{
      public static void main(String argv[]) throws Exception{
            A a = new A();
            Thread t = new Thread(a, "A");
            Thread t1 = new Thread(a, "B");
            t.start();
            t.join();
            t1.start();
      }
}

A A A A B B B B
A B A B A B A B
Output order is not guaranteed
Compilation succeed but Runtime Exception
None of these

Explanation

Q.12.

What will be the output?

class A extends Thread{
      public void run(){
            for(int i=0; i<2; i++){
                  System.out.println(i);
            }
      }
}

public class Test{
      public static void main(String argv[]){
            Test t = new Test();
            t.check(new A(){});
      }
      public void check(A a){
            a.start();
      }
}

0 0
Compilation error, class A has no start method
0 1
Compilation succeed but runtime exception
None of these

Explanation

Q.13.

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

class A implements Runnable{
      public void run(){
            System.out.println("run-A");
      }
}

1. public class Test{
2.       public static void main(String argv[]){
3.             A a = new A();
4.             Thread t = new Thread(a);
5.             System.out.println(t.isAlive());
6.             t.start();
7.             System.out.println(t.isAlive());
8.       }
9. }

false run-A true
false run-A false
true run-A true
Compilation fails due to an error on line 7
None of these

Explanation

Q.14.

Which of the following are methods of the Thread class?
1) yield()
2) sleep(long msec)
3) go()
4) stop()

1 , 2 and 4
1 and 3
3 only
None of the above

Q.15.

Analyze the following code:

public class Test implements Runnable{
        public static void main(String[] args){
                Test t = new Test();
        }

        public Test(){
                Thread t = new Thread(this);
                t.start();
        }

        public void run(){
                System.out.println("test");
        }
}

The program has a compilation error because t is defined in both the main() method and the constructor Test().
The program compiles fine, but it does not run because you cannot use the keyword this in the constructor.
The program compiles and runs and displays nothing.
The program compiles and runs and displays test.

Q.16.

What will be the output?

class One extends Thread{
	public void run(){
		for(int i=0; i<2; i++){
			System.out.print(i);
		}
	}
}

public class Test{
	public static void main(String args[]){
		Test t = new Test();
		t.call(new One());
	}
	
	public void call(One o){
		o.start();
	}
}

0 0
Compilation Error
0 1
None of these

Q.17.

What will happen after compiling and running following code?

class A implements Runnable{
      public void run(){
            System.out.println("run-a");
      }
}

1. public class Test{
2.       public static void main(String... args){
3.             A a = new A();
4.             Thread t = new Thread(a);
5.             t.start();
6.             t.start();
7.       }
8. }

run-a
run-a run-a
Compilation fails with an error at line 6
Compilation succeed but Runtime Exception
None of these

Explanation

Support mcqgeeks.com by disabling your adblocker.