Java Programming Language

Java thread MCQ

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Evaluate your understanding of Java threads with these multiple choice questions. Learn about the different methods for creating and managing threads in Java and how to use them to build efficient and responsive Java programs. Take the quiz now! ➲ Java thread MCQ - Quiz

Q 1: Which of the following constructor of class Thread is valid one?

  • A Thread(Runnable threadOb, int priority)
  • B Thread(int priority)
  • C Thread(Runnable threadOb, String threadName)
  • D Thread(String threadName, int priority)

Q 2: When a class extends the Thread class, it should override ............ method of Thread class to start that thread.

  • A start()
  • B run()
  • C init()
  • D go()

Q 3: In java, a thread can be created by ..........

  • A Extending the thread class.
  • B Implementing Runnable interface.
  • C Both of the above
  • D None of these

Q 4: What will be the output of the following program code? 
public class Test implements Runnable{
        public static void main(String[] args){
                Thread t = new Thread(this);
                t.start();
        }

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

  • A The program does not compile because this cannot be referenced in a static method.
  • B The program compiles fine, but it does not print anything because t does not invoke the run() method
  • C The program compiles and runs fine and displays test on the console.
  • D None of the above

Q 5: Analyze the following code: 
public abstract class Test implements Runnable{
        public void doSomething() { };
}

  • A The program will not compile because it does not implement the run() method.
  • B The program will not compile because it does not contain abstract methods.
  • C The program compiles fine.
  • D None of the above

Q 6: 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. }

  • A run-a
  • B run-a run-a
  • C Compilation fails with an error at line 6
  • D Compilation succeed but Runtime Exception

Q 7: 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. }

  • A run-test run-test
  • B run-test
  • C Compilation fails due to an error on line 4
  • D Compilation fails due to an error on line 7

Q 8: 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();
	}
}

  • A 0 0
  • B Compilation Error
  • C 0 1
  • D None of these

Q 9: 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");
        }
}

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

Q 10: Analyze the following code: 
public class Test implements Runnable{
        public static void main(String[] args){
                Test t = new Test();
                t.start();
        }

        public void run() { }
}

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

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 A B B B B
  • B A B A B A B A B
  • C Output order is not guaranteed
  • D Compilation succeed but Runtime Exception

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();
      }
}

  • A 0 0
  • B Compilation error, class A has no start method
  • C 0 1
  • D Compilation succeed but runtime exception

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. }

  • A false run-A true
  • B false run-A false
  • C true run-A true
  • D Compilation fails due to an error on line 7

Q 14: Which of the following are methods of the Thread class?

1) yield()
2) sleep(long msec)
3) go()
4) stop()

  • A 1 , 2 and 4
  • B 1 and 3
  • C 3 only
  • D None of the above

Q 15: What notifyAll() method do?

  • A Wakes up one threads that are waiting on this object's monitor
  • B Wakes up all threads that are not waiting on this object's monitor
  • C Wakes up all threads that are waiting on this object's monitor
  • D None of the above

Q 16: 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");
      }
}

  • A Compilation fails.
  • B An exception is thrown at runtime.
  • C "BeginRunEnd" is printed.
  • D "BeginEndRun" is printed.

Q 17: 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);
      }
}

  • A Prints
  • B Prints
  • C Prints
  • D Compiler error

Q 18: 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. }

  • A good
  • B null
  • C Compilation fails with an error at line 5
  • D Compilation succeed but Runtime Exception

Q 19: Which keyword when applied on a method indicates that only one thread should execute the method at a time.

  • A volatile
  • B synchronized
  • C native
  • D static

Q 20: 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 A compile time error indicating that no run method is defined for the Thread class
  • B A run time error indicating that no run method is defined for the Thread class
  • C Clean compile and at run time the values 0 to 9 are printed out
  • D Clean compile but no output at runtime

Q 21: What will be the 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();
      }
}

  • A Compilation fails.
  • B An exception is thrown at runtime.
  • C "go" is printed
  • D "gogogo" is printed

Q 22: 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");
      }
}

  • A Compilation fails.
  • B An exception is thrown at runtime.
  • C "BeginRunEnd" is printed.
  • D "BeginEndRun" is printed.