What is the correct order of JDBC operations?

The correct answer is A: Load Driver → Create Connection → Create Statement → Execute Query → Close Resources. The correct JDBC sequence is: 1) Load the JDBC driver, 2) Create connection, 3) Create statement, 4) Execute query, 5) Process results, 6) Close resources.

Consider a scenario where you're processing a 5GB log file and need to count specific error messages. Which I/O strategy would be most memory-efficient?

The correct answer is B: Use BufferedReader with readLine() in a loop to process line-by-line. BufferedReader with readLine() processes the file line-by-line, maintaining a constant memory footprint regardless of file size. Options A, C, and D would attempt to load the entire 5GB file into memory, causing OutOfMemoryError. This is the standard approach for large file processing.

When implementing Externalizable interface, which method is mandatory?

The correct answer is C: writeExternal() and readExternal(). Externalizable requires implementation of writeExternal() and readExternal() for complete control over serialization.

What will be the behavior if an exception is thrown in the finally block?

The correct answer is B: It will replace any exception thrown in try/catch blocks. If an exception occurs in finally, it will propagate and override any previous exception from try/catch blocks. However, in try-with-resources, exceptions are suppressed.

What is the output of this code? Consumer print = s -> System.out.println(s.toUpperCase()); print.accept("java");

The correct answer is B: JAVA. Consumer accepts one argument and returns nothing. print.accept("java") calls lambda which prints s.toUpperCase() = "JAVA".

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Java Programming
Generics

Java OOP, collections, multithreading

25 Q 10 Topics Take Mock Test

Difficulty: All Easy Medium Hard 21–25 of 25

Topics in Java Programming

All Basics & Syntax 100 OOP in Java 100 Collections Framework 100 Multithreading 100 Exception Handling 100 I/O Streams 100 JDBC 100 Generics 100 Lambda Expressions 100 Spring Framework Basics 58

Q.21 Easy Generics

What is the output of this generic code?
class Pair {
public void display(K key, V value) {
System.out.println(key + ": " + value);
}
}
Pair p = new Pair();
p.display("Age", 25);

A Age: 25

B Compilation error - type mismatch

C Age: 25.0

D Runtime exception

Correct Answer: A. Age: 25

EXPLANATION

The generic class Pair with two type parameters K and V correctly accepts String and Integer. The display method prints the key-value pair.

Test

Q.22 Easy Generics

Which of the following is a valid generic method declaration?

A public T getValue(T value) { return value; }

B public T getValue(T value) { return value; }

C public getValue(T value) { return value; }

D public getValue(T value) { return value; }

Correct Answer: A. public T getValue(T value) { return value; }

EXPLANATION

The correct syntax for a generic method is: access_modifier <T> returnType methodName(T parameter). The type parameter <T> must come before the return type.

Test

Q.23 Easy Generics

What will be the output of the following code?
List list = new ArrayList();
list.add("Java");
System.out.println(list.get(0).length());

A 4

B 5

C Compilation error

D Runtime exception

Correct Answer: A. 4

EXPLANATION

"Java" has 4 characters. The generic type ensures the element is a String, so .length() method is available without casting.

Test

Q.24 Easy Generics

Which keyword is used to declare a generic class in Java?

B generic

C template

D type

Correct Answer: A.

EXPLANATION

<T> is the standard syntax for declaring a generic type parameter in Java classes.

Test

Q.25 Easy Generics

What is the primary purpose of Generics in Java?

A To provide type safety and eliminate type casting

B To increase memory allocation

C To reduce code compilation time

D To automatically manage garbage collection

Correct Answer: A. To provide type safety and eliminate type casting

EXPLANATION

Generics enable type safety at compile time and eliminate the need for explicit type casting, reducing runtime errors.

Test

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Generics