Given: Function f = x -> x * 2; Integer result = f.apply(5); What is the value of result?

The correct answer is B: 10. The lambda expression x -> x * 2 multiplies the input by 2. When applied to 5, it returns 10.

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".

Which functional interface is used for operations that take two arguments and return a single value?

The correct answer is B: BiFunction. BiFunction represents a function that accepts two arguments of types T and U, and returns a result of type R.

What will be the output? try { throw new Exception("Test"); } catch(Exception e) { System.out.println("Caught"); throw new RuntimeException("New"); } finally { System.out.println("Finally"); }

The correct answer is A: Caught Finally followed by RuntimeException. The finally block executes after catch block. 'Caught' is printed, then finally block prints 'Finally', and then RuntimeException is thrown.

Consider the code: java List list = new ArrayList(); Will this compile?

The correct answer is B: No, ArrayList is not compatible with List. Generics are invariant. ArrayList cannot be assigned to List even though Integer is a subtype of Number. This prevents type safety issues.

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Java Programming
Basics & Syntax

Java OOP, collections, multithreading

50 Q 10 Topics Take Mock Test

Difficulty: All Easy Medium Hard 41–50 of 50

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.41 Medium Basics & Syntax

What will be the output: System.out.println('A' + 'B');

A AB

B 131

C Error

D 2

Correct Answer: B. 131

EXPLANATION

Characters are treated as their ASCII values in arithmetic operations. 'A' (65) + 'B' (66) = 131.

Test

Q.42 Medium Basics & Syntax

Which of the following is the correct way to declare and initialize an array in Java?

A int array[5] = {1, 2, 3, 4, 5};

B int[] array = {1, 2, 3, 4, 5};

C int array = [1, 2, 3, 4, 5];

D array[5] int = {1, 2, 3, 4, 5};

Correct Answer: B. int[] array = {1, 2, 3, 4, 5};

EXPLANATION

The correct syntax is 'datatype[] arrayName = {elements};' or 'datatype[] arrayName = new datatype[size];'

Test

Q.43 Medium Basics & Syntax

Identify the output: System.out.println("Java".length());

A 4

B 5

C Compilation error

D null

Correct Answer: A. 4

EXPLANATION

The length() method returns the number of characters in the string "Java", which is 4 characters.

Test

Q.44 Medium Basics & Syntax

Which statement is correct about Java variables?

A Variable names are case-sensitive

B Variable names can start with a digit

C Variable names can contain spaces

D Variable names can use special characters like @, #

Correct Answer: A. Variable names are case-sensitive

EXPLANATION

Java variable names are case-sensitive. 'age' and 'Age' are different variables. Names cannot start with digits, cannot contain spaces, and special characters are not allowed.

Test

Q.45 Medium Basics & Syntax

What is the output of: System.out.println(5 > 3 ? 'A' : 'B');

A A

B B

C true

D Compilation error

Correct Answer: A. A

EXPLANATION

The ternary operator (?:) evaluates the condition (5 > 3, which is true) and returns the first value 'A'.

Test

Q.46 Medium Basics & Syntax

Which operator has the highest precedence in Java?

A * / %

B + -

C () []

D == !=

Correct Answer: C. () []

EXPLANATION

Parentheses () and array access [] have the highest precedence in Java. Multiplication, division, and modulo come next, followed by addition and subtraction.

Test

Q.47 Medium Basics & Syntax

What is the output of: System.out.println(10 / 3);

A 3.33

B 3

C 3.0

D 3.333333

Correct Answer: B. 3

EXPLANATION

When both operands are integers, the division result is an integer. 10 / 3 = 3 (integer division, not floating-point).

Test

Q.48 Medium Basics & Syntax

Which of the following will compile without error? public static void main(String args[]) { int x = 10; final int y = 20; y = 30; }

A Yes, it will compile

B No, compilation error on y = 30

C No, compilation error on final declaration

D No, compilation error on main method

Correct Answer: B. No, compilation error on y = 30

EXPLANATION

Once a final variable is assigned, it cannot be reassigned. The line 'y = 30;' will cause a compilation error.

Test

Q.49 Medium Basics & Syntax

What is the size of 'char' data type in Java?

A 1 byte

B 2 bytes

C 4 bytes

D 8 bytes

Correct Answer: B. 2 bytes

EXPLANATION

The 'char' data type in Java is 2 bytes (16 bits) because it uses Unicode character encoding.

Test

Q.50 Medium Basics & Syntax

Which of the following is NOT a primitive data type in Java?

A int

B boolean

C String

D double

Correct Answer: C. String

EXPLANATION

String is a non-primitive (reference) data type in Java. Primitive types include int, boolean, double, float, char, long, short, byte.

Test

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