Intermediate level java quiz

Which of the following statements about interfaces in Java is true?

An interface can extend multiple classes

An interface can extend multiple other interfaces

An interface can implement multiple classes

An interface can be instantiated directly

Which of the following is true about the `this` keyword in Java?

It refers to the current class instance

It refers to the current method

It refers to the superclass

It refers to the class itself

What will be the result of the following code? int[] arr = {1, 2, 3}; System.out.println(arr[3]);

1

2

3

ArrayIndexOutOfBoundsException

Which of the following is the correct way to handle multiple exceptions in a single `catch` block in Java 7 or later?

catch (IOException | SQLException e) {}

catch (IOException & SQLException e) {}

catch (IOException, SQLException e) {}

catch (IOException, SQLException | NullPointerException e) {}

Which of the following collection types is used to store key-value pairs in Java?

List

Set

Map

Queue

What is the purpose of the `clone()` method in Java?

To copy a class definition

To create a new instance of a class

To create a copy of an object

To make a class immutable

Which of the following statements about the `synchronized` keyword is true in Java?

It is used to lock a method or block of code for thread safety

It is used to make a method execute in parallel

It is used to execute multiple methods concurrently

It is used to synchronize data in a database

What is the output of the following code? String str = "Java"; str = str.concat(" Programming"); System.out.println(str);

Java Programming

JavaProgramming

Compilation error

Runtime exception

Which of the following is used to define a custom exception in Java?

Extend the `Exception` class

Implement the `Throwable` interface

Use the `CustomException` class

Extend the `RuntimeException` class

Which of the following is true about Java's `HashMap`?

It maintains the order of elements based on their keys

It allows duplicate keys

It allows duplicate values

It is synchronized