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Java Basics

1/25 What is the purpose of the 'finalize' method in Java?
- To initialize variables
- To clean up resources before an object is garbage collected
- To finalize a class definition
- To finalize variable assignments
2/25 Which of these is not a valid Java access modifier?
- public
- protected
- private
- friend
3/25 Which Java feature allows the method of a subclass to override the method of its superclass?
- Inheritance
- Encapsulation
- Polymorphism
- Abstraction
4/25 In Java, which of the following is a valid way to declare an array?
- int array[5];
- int[] array = new int[5];
- array = new int[5];
- int array[] = new int[5];
5/25 Which exception is thrown when trying to access an element with a key that does not exist in a HashMap?
- NullPointerException
- ArrayIndexOutOfBoundsException
- KeyNotFoundException
- NoSuchElementException
6/25 Which of these data types is used to represent a single character in Java?
- String
- char
- Character
- byte
7/25 How do you handle exceptions in Java?
- Using try-catch blocks
- By using the 'throws' keyword
- By using the 'extends' keyword
- By declaring them as static
8/25 What is the function of the 'extends' keyword in Java?
- To inherit methods from an interface
- To extend a method's functionality
- To inherit properties and methods from a superclass
- To extend the memory allocation for an object
9/25 Which of these is an immutable class in Java?
- java.lang.StringBuilder
- java.lang.String
- java.lang.StringBuffer
- java.util.ArrayList
10/25 In Java, what is the difference between '==' and 'equals()'?
- '==' checks for value equality, 'equals()' checks for reference equality
- '==' checks for reference equality, 'equals()' checks for value equality
- There is no difference
- 'equals()' is used only for strings
11/25 Which method must be implemented in a class that implements the java.util.Comparator interface?
- compare()
- compareTo()
- equals()
- hashCode()
12/25 In Java, what is the purpose of the Collections.sort() method?
- To sort elements of a collection in descending order
- To randomly shuffle elements of a collection
- To sort elements of a collection in ascending order
- To reverse the order of elements in a collection
13/25 What is the role of the 'break' statement in a loop in Java?
- To skip the current iteration of the loop
- To pause the loop execution temporarily
- To terminate the loop immediately
- To continue loop execution indefinitely
14/25 What is the concept of 'overloading' in Java?
- Assigning extra resources to a Java application
- Creating multiple methods in a class with the same name but different parameters
- Increasing the memory allocation to a Java program
- Replacing a method in a subclass with a method from the superclass
15/25 What is the primary difference between 'StringBuffer' and 'StringBuilder' in Java?
- StringBuffer is mutable, while StringBuilder is immutable
- StringBuilder is faster as it is not synchronized
- StringBuffer can store characters, while StringBuilder cannot
- StringBuilder is thread-safe, while StringBuffer is not
16/25 In Java, which method you must override to use an object as a key in a HashMap?
- hashKey()
- mapKey()
- equals() and hashCode()
- getKey()
17/25 In Java, what is the effect of assigning a 'null' value to a reference variable?
- The reference variable is deleted
- It causes a compile-time error
- The reference variable points to no object
- It automatically initializes the object
18/25 What is the difference between 'static' and 'non-static' methods in Java?
- Static methods can be called without creating an instance of the class
- Non-static methods are always synchronized
- Static methods are faster
- Non-static methods can access any class variable
19/25 What does the 'throws' keyword do in Java?
- Automatically handles an exception
- Declares an exception which might be thrown
- Stops the propagation of an exception
- Increases the throw range of an exception
20/25 What does the 'final' keyword indicate when applied to a method in Java?
- The method can be overridden in a subclass
- The method cannot be overridden in a subclass
- The method will return a final value
- The method will be executed at the end of the program
21/25 Which method in the Object class is used to obtain a unique hash code for the object?
- uniqueCode()
- hashCode()
- identityHashCode()
- getObjectHash()
22/25 How can you achieve thread safety in Java?
- By using synchronized blocks or methods
- By avoiding the use of multiple threads
- By using the 'volatile' keyword
- By making all methods and variables private
23/25 What is the use of the 'implements' keyword in Java?
- To inherit from an abstract class
- To include an interface in a class
- To mark a method as mandatory to override
- To declare a class as abstract
24/25 In Java, what is the function of the 'super' keyword?
- To call a method of the superclass
- To declare superior variables
- To access the superclass's static methods
- To create an object of the superclass
25/25 What is the use of the 'protected' access modifier in Java?
- To restrict access to the class members within its own class only
- To provide access to the class members within the same package and subclasses
- To provide universal access from any other class
- To prevent modification of the class members
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