Java Quizz Dive into our tech quiz zone and put your technical skills to the test! Our quizzes cover a wide array of technical topics, perfect for sharpening your knowledge and challenging your understanding. Compete with others, see your rankings, and boost your technical proficiency. Start quizzing today! 1 / 56 1. What will be the output of the below statements? public class Test { public static void main(String[] args) { String s1 = "abc"; StringBuffer s2 = new StringBuffer(s1); System.out.println(s1.equals(s2)); } } ClassCastException at runtime false true Compile-time error 2 / 56 2. What will be the output of the below statements? public class Test { public static void main(String[] args) { String s1 = null; System.out.println(s1); //line 2 System.out.println(s1.toString()); //line 3 } } NullPointerException NullPointerException null null None null NullPointerException 3 / 56 3. What is the output of the following program? public class Question { T t; public static void main(String[] args) { Question q = new Question(); // 1 q.t = new Float(1); // 2 System.out.println(q.t); } } Compilation fails on the line marked as // 2 1.0 An exception occurs at runtime Compilation fails on the line marked as // 1 4 / 56 4. Which method is used to start a thread in Java? init() run() execute() start() 5 / 56 5. Consider the following program and predict the output: class MyThread extends Thread { @Override public void run() { System.out.println("In run method; thread name is: " + Thread.currentThread().getName()); } } public class ThreadTest { public static void main(String args[]) { Thread myThread = new MyThread(); myThread.run(); // #1 System.out.println("In main method; thread name is: " + Thread.currentThread().getName()); } } The program results in a runtime exception. The program prints: In the run method; the thread name is: thread-0 In the main method; the thread name is: main The program results in a compiler error at statement #1. The program prints the following: In run method; thread name is: main In main method; thread name is: main 6 / 56 6. Consider the following program and choose the right option: class MyThread extends Thread { public void run() { System.out.println("Running"); } } public class ThreadTest { public static void main(String args[]) throws InterruptedException { Runnable r = new MyThread(); // #1 Thread myThread = new Thread(r); // #2 myThread.start(); } } The program will result in a compilation error at statement #1. The program will compile with no errors but does not print any output in the console. The program will result in a compilation error at statement #2. The program will compile with no errors and will print “Running” in the console. 7 / 56 7. Which one of the following options correctly describes the behavior of this program? When executed, the program throws an IllegalMonitorStateException. When executed, the program prints “Worker ” and then terminates. When executed, the program prints “Worker ”, and after that the program hangs (i.e., does not terminate). The program does not compile and fails with multiple compiler errors. When executed, the program prints the following: “Worker Master ”. 8 / 56 8. Which method is used to transform each element of a Stream using a provided function? map reduce flatMap filter 9 / 56 9. Which method is used to transform each element of a Stream using a provided function? map flatMap reduce filter 10 / 56 10. Which of the following state(s) is/are NOT legitimate thread state(s)? (Select all that apply.) TERMINATED WAITING NEW RUNNABLE EXECUTING 11 / 56 11. Which of the following are valid ChronoUnit values for LocalTime? NANOS Both B & D DAY HALF_DAYS YEAR 12 / 56 12. What is the main advantage of multithreading in Java? Elimination of runtime errors. Reduced memory usage. Simplified program structure. Improved program performance. 13 / 56 13. Which of the following type of JDBC driver, uses database native protocol? JDBC-Net, pure Java driver Native-protocol, pure Java driver JDBC-ODBC Bridge plus ODBC driver Native-API, partly Java driver 14 / 56 14. What type of operation is Stream.filter? Terminal Mutable Intermediate Source 15 / 56 15. Which of the following are valid ChronoField values for LocalDate? Both A & C DAY_OF_MONTH MILLI_OF_SECOND HOUR_OF_DAY DAY_OF_WEEK 16 / 56 16. In which of the following type of ResultSet, the cursor can only move forward in the result set? None of the above. ResultSet.TYPE_FORWARD_ONLY ResultSet.TYPE_SCROLL_INSENSITIVE ResultSet.TYPE_SCROLL_SENSITIVE 17 / 56 17. Which method is used to start the execution of a thread? run() begin() start() execute() 18 / 56 18. What is the maximum number of threads that can be created in a Java program? It is limited to 100 threads. It depends on the amount of available memory. It depends on the number of CPU cores. There is no fixed limit. 19 / 56 19. Which of the following is a valid lambda expression? All of the above x -> x*x (x, y) -> return x + y; (int x, int y) -> x + y 20 / 56 20. What will be the output of the following code? String str = "Hello"; str.concat(" World"); System.out.println(str); Hello World World Compilation Error Hello 21 / 56 21. Consider the following program and predict the output: class MyThread extends Thread { public MyThread(String name) { this.setName(name); start(); System.out.println("in constructor " + getName()); } @Override public void start() { System.out.println("in start " + getName()); } public void run() { System.out.println("in run " + getName()); } } public class ThreadTest { public static void main(String[] args) { new MyThread("oops"); } } in start oops in run oops in constructor oops in constructor oops in start oops in run oops in start oops in constructor oops in run oops in start oops in constructor oops 22 / 56 22. Lambda expressions can be used with the Java Collections API primarily in ... Iterating Sorting All of the above Filtering 23 / 56 23. Given List list = new ArrayList(); // 1 list.add(new Integer(2)); // 2 list.add(new Object()); // 3 Which line will generate a compile-time error? Line marked as // 3 No compile-time error is generated Line marked as // 1 Line marked as // 2 24 / 56 24. What is the purpose of the wait() method in Java threads? To pause the execution of a thread. To notify other threads to resume execution. To terminate a thread. To release the lock held by the thread. 25 / 56 25. Consider the following program and predict the output: class MyThread implements Runnable { @Override public void run() { System.out.println(Thread.currentThread().getName()); } } public class ThreadTest { public static void main(String arg[]) { Thread thread = new Thread(new MyThread()); thread.run(); thread.run(); thread.start(); } } main Thread-0 Thread-1 Thread-0 Thread-1 Thread-2 main main Thread-0 Thread-0 main Thread-1 26 / 56 26. Which of the following methods can be used to make a thread pause execution for a specific amount of time? yield() pause() sleep() wait() 27 / 56 27. Which of these collectors is used for grouping elements of a Stream? Collectors.joining() Collectors.toList() Collectors.groupingBy() Collectors.toSet() 28 / 56 28. Which of the following statements are true? Curly brackets are required whenever the return keyword is used in a lambda expression A return keyword is always optional in a lambda expression A return keyword is always required in a lambda expression Lambda expressions don't return values 29 / 56 29. Consider the following program and choose the correct answer: class MyThread extends Thread { public MyThread(String name) { this.setName(name); } @Override public void run() { try { sleep(100); } catch (InterruptedException e) { e.printStackTrace(); } play(); } private void play() { System.out.print(getName()); System.out.print(getName()); } } public class ThreadTest { public static void main(String args[]) throws InterruptedException { Thread tableThread = new MyThread("Table"); Thread tennisThread = new MyThread("Tennis"); tableThread.start(); tennisThread.start(); } } The output of this program cannot be predicted; it depends on thread scheduling. This program will always print the following: Tennis Tennis Table Table. This program will throw an IllegalStateException. This program will always print the following: Table Table Tennis Tennis. 30 / 56 30. Which of these is a terminal operation in the Stream API? filter map flatMap forEach 31 / 56 31. What is the output of the following code? try { int a = 10 / 0; } catch (ArithmeticException e) { System.out.println("Exception caught"); } finally { System.out.println("Finally block"); } Finally block Finally block Exception caught Exception caught 32 / 56 32. Consider the following program and predict the output: public class Test { public static void main(String[] args) { String s = new String("5"); System.out.println(1 + 10 + s + 1 + 10); } } 27 115110 11511 1105110 33 / 56 33. Select all the classes that extend the String class StringBuilder None StringWriter StringBuffer 34 / 56 34. Which method is used to compare two strings, ignoring case considerations? equals() equalsIgnoreCase() compareTo() compareToIgnoreCase() 35 / 56 35. You cannot use ... inside lambda expressions. break and continue return statement arithmetic operations this keyword 36 / 56 36. Consider the following program and predict its output: public class Test { public static void main(String[] args) { String str = null; switch (str) { // #1 case "null": System.out.println("null string"); // #2 break; } } } This program results in a compiler error in statement #1. This program results in a compiler error in statement #2. This program results in throwing a NullPointerException. This program prints the following: null string. 37 / 56 37. Which of the following is a checked exception? NullPointerException IOException ArithmeticException ArrayIndexOutOfBoundsException 38 / 56 38. Consider the following program: public class StrEqual { public static void main(String[] args) { String s1 = "hello"; String s2 = new String("hello"); String s3 = "hello"; if (s1 == s2) { System.out.println("s1 and s2 equal"); } else { System.out.println("s1 and s2 not equal"); } if (s1 == s3) { System.out.println("s1 and s3 equal"); } else { System.out.println("s1 and s3 not equal"); } } } Which one of the following options provides the output of this program when executed? s1 and s2 equal s1 and s3 not equal s1 and s2 not equal s1 and s3 not equal s1 and s2 not equal s1 and s3 equal s1 and s2 equal s1 and s3 equal 39 / 56 39. What is the output of the following program? public class Question { public static void main(String[] args) { Question q = new Question(); List l = new ArrayList(); l.add(20); l.add(30); q.m1(l); } private void m1(List l) { m2(l); // 1 } private void m2(List l) { l.set(1, l.get(0)); // 2 System.out.println(l); } } Compilation fails on the line marked as // 2 [20, 20] Compilation fails on the line marked as // 1 An exception occurs at runtime 40 / 56 40. What is the output of the following code? int[] arr = {1, 2, 3, 4, 5}; System.out.println(arr[2]); 2 4 1 3 41 / 56 41. Which of the following keywords is used to manually throw an exception? try catch throws throw 42 / 56 42. What is the default priority of a thread in Java? 0 10 1 5 43 / 56 43. What is the purpose of the Stream.flatMap method? To replace each element with a stream and then flatten the streams into a single stream To merge multiple streams into one To map each element to a new value To filter elements based on a flat structure 44 / 56 44. Consider this code segment? DateTimeFormatter formatter = DateTimeFormatter.ofPattern("EEEE", Locale.US); System.out.println(formatter.format(LocalDateTime.now())); Which of the following outputs matches the string pattern "EEEE" given in this code segment? F Sept Friday September 45 / 56 45. What does the following lambda expression represent? () -> {} A lambda that does nothing and returns void None of the above A lambda that throws an exception A lambda that accepts two parameters and does nothing 46 / 56 46. What is the main purpose of the Stream.sorted method? To sort the elements of the stream in their natural order or by a provided comparator To randomly shuffle the elements of the stream To reverse the order of elements in the stream To remove duplicate elements from the stream 47 / 56 47. Which of the following is correct about Statement class of JDBC? Statement encapsulates an SQL statement which is passed to the database to be planned and executed. Statement encapsulates an SQL statement which is passed to the database to be parsed and compiled. Both of the above. none of the above. 48 / 56 48. How can synchronization be achieved in Java threads? Using the static keyword. Using the synchronized keyword. Using the final keyword. Using the volatile keyword. 49 / 56 49. Which of the following is correct about setFetchSize(int)? Both of the above. setFetchSize(int) affects how the database returns the ResultSet data. None of the above. setFetchSize(int) defines the number of rows that will be read from the database when the ResultSet needs more rows. 50 / 56 50. Which of the following correctly declares an array of integers in Java? int arr = new int[10]; All of the above int arr[]; int[] arr; 51 / 56 51. Which one of the following classes is best suited for storing timestamp values of application events in a file? java.time.Period class java.time.Duration class java.time.Instant class java.time.ZoneId class java.time.ZoneOffset class 52 / 56 52. What is the purpose of the join() method in Java threads? To interrupt the execution of a thread. To wait for a thread to finish its execution. To schedule the execution of a thread. To notify a thread to stop execution. 53 / 56 53. What does the Stream.peek method do? Consumes and removes an element from the stream Filters elements based on a predicate Performs an action on each element of the stream without modifying it Reduces the stream to a single summary element 54 / 56 54. What is the result of applying the Stream.reduce operation? An Optional describing the reduced value, if any A new stream with elements reduced according to a provided accumulator function A list of elements that were reduced A boolean indicating if any stream elements match a given predicate 55 / 56 55. Which of the following is correct about PreparedStatement? Both of the above. PreparedStatement allows mapping different requests with same prepared statement but different arguments to execute the same execution plan. Prepared statements are more secure because they use bind variables, which can prevent SQL injection attack. None of the above. 56 / 56 56. Which of the following statements correctly describes the behavior of this program? This program will print null in the console. This program will throw a NullPointerException. This program will print 10 in the console. This program will result in a compiler error. Your score is 0%
