The Java Certified Foundations Associate certification is an excellent starting point to validate your foundational knowledge and boost your career prospects. To help you in this quest, we have compiled a practice test of 25 multiple-choice questions, each accompanied by answers and explanations. Let’s dive in and start coding your success!
1. What is the default value of an instance variable of type int in Java?
Answer:
Explanation:
In Java, the default value of an instance variable of type int is 0. Instance variables are given default values when they are declared and not explicitly initialized.
2. Which of the following is a valid method declaration in Java?
Answer:
Explanation:
All of the given options are valid method declarations in Java. A method must have a return type, a name, and a parameter list enclosed in parentheses.
3. How do you create a single-line comment in Java?
Answer:
Explanation:
In Java, single-line comments are created using two forward slashes (//), followed by the comment.
4. Which of the following Java keywords is used to define a constant variable?
Answer:
Explanation:
The "final" keyword in Java is used to create constant variables. Once a final variable is assigned a value, it cannot be modified.
5. What is the output of the following Java code snippet?
int x = 10;
int y = ++x;
System.out.println(y);
Answer:
Explanation:
The code will output 11. The prefix increment operator (++) will increment the value of x before assigning it to y.
6. What is the role of the Java Virtual Machine (JVM)?
Answer:
Explanation:
The Java Virtual Machine (JVM) is a runtime environment that interprets and executes Java bytecode, enabling Java programs to be platform-independent.
7. Which of the following is a correct way to allocate memory to an array in Java?
Answer:
Explanation:
In Java, memory for an array can be allocated using the ‘new’ keyword followed by the data type and the size of the array enclosed in square brackets.
8. How can you handle exceptions in Java?
Answer:
Explanation:
In Java, exceptions can be handled using try and catch blocks. The code that might throw an exception is placed inside the try block, and the code to handle the exception is placed inside the catch block.
9. Which of the following is an interface in the Java Collections Framework?
Answer:
Explanation:
In the Java Collections Framework, List is an interface, whereas ArrayList, HashMap, and TreeMap are classes.
10. What is the purpose of the ‘this’ keyword in Java?
Answer:
Explanation:
The ‘this’ keyword in Java is used to refer to the current object within an instance method or constructor.
11. Which of the following is true about method overloading in Java?
Answer:
Explanation:
Method overloading in Java occurs when a class has multiple methods with the same name but different parameter lists. The return type is not considered while differentiating overloaded methods.
12. What is encapsulation in Java?
Answer:
Explanation:
Encapsulation is one of the four fundamental OOP concepts. The other three are inheritance, polymorphism, and abstraction. It refers to the bundling of data and the methods that operate on that data, restricting the access to some of the object's components, which is a means of preventing unintended interference and misuse of the data.
13. Which Java feature allows one interface to inherit from another interface?
Answer:
Explanation:
In Java, one interface can inherit from another interface using the extends keyword. This is a form of inheritance, which is a fundamental concept of object-oriented programming.
14. Which of the following statements is true about constructors in Java?
Answer:
Explanation:
A constructor in Java is a special method used to initialize objects. It is called when an instance of an object is created and doesn’t have a return type.
15. What is the output of the following Java code snippet?
String str1 = "Java";
String str2 = "Java";
System.out.println(str1 == str2);
Answer:
Explanation:
The output will be true because both str1 and str2 refer to the same object in the String constant pool.
16. In Java, which method must be implemented by a class using the Runnable interface for creating a thread?
Answer:
Explanation:
In Java, a class that implements the Runnable interface must override the run() method. This method contains the code that constitutes the new thread’s body.
17. Which class should be used to perform operations such as reading and writing data to/from files in Java?
Answer:
Explanation:
In Java, FileReader is used for reading character files, and FileWriter is used for writing characters to a file. Being Reader derived, FileReader makes the form of characters correct and provides efficient reading of characters, arrays, and lines.
18. How can we ensure that a resource is closed automatically when try block finishes, and we don’t need to close it explicitly?
Answer:
Explanation:
In Java 7 and later, we can use the try-with-resources statement to automatically close resources like File, Socket, etc., when the try block finishes, and there is no need to close them explicitly.
19. Which of the following loops will execute the statements within it at least once?
Answer:
Explanation:
In Java, a do-while loop is guaranteed to execute the statements within it at least once, because the condition is checked after the body of the loop is executed.
20. Which of the following Java operators is used to allocate memory for an object?
Answer:
Explanation:
In Java, the "new" operator is used to allocate memory for an object and invoke the object's constructor.
21. What will be the result of compiling and running the following Java code snippet?
public class Test {
public static void main(String[] args) {
System.out.println(args[0]);
}
}
Answer:
Explanation:
The code will compile successfully, but at runtime, it will throw an ArrayIndexOutOfBoundsException since no command-line argument is provided.
22. Which of the following access modifiers allows a member to be accessed by any other code in the same package?
Answer:
Explanation:
In Java, if a member does not have any access modifier, it is given default access level. The default access level allows a member to be accessed by any other code in the same package.
23. In Java, if a class has multiple constructors, what is this concept called?
Answer:
Explanation:
In Java, if a class has more than one constructor, it is known as constructor overloading. It allows a class to have multiple constructors with different parameter lists.
24. What is the initial default capacity of Java's StringBuilder class when no capacity is defined?
Answer:
Explanation:
When no capacity is defined, the StringBuilder class in Java initializes with a default capacity of 16.
25. Which of the following collections in Java implements the Queue interface?
Answer:
Explanation:
In Java, both PriorityQueue and LinkedList implement the Queue interface. PriorityQueue is a class in the Java Collections Framework that implements a priority queue, and LinkedList is a class that implements a doubly-linked list, but also implements the Queue interface.
By navigating through this comprehensive set of questions and detailed explanations, you are well on your way to solidifying your foundation in Java programming. As you prepare for the Java Certified Foundations Associate Certification, it is essential to revisit these concepts, understand the underlying principles, and practice coding. Keep exploring, practicing, and challenging yourself with more complex scenarios. Your dedication and curiosity will be your greatest allies in acing the certification exam and beyond. Happy Learning!