Which scenario would cause a StackOverflowError in Java exception handling?

The correct answer is B: A method recursively catching and rethrowing the same exception infinitely. StackOverflowError occurs when stack memory exhausts due to deep recursion. If a method catches an exception and immediately rethrows it without modification, calling itself, stack frames accumulate until overflow. This is a runtime error, not a checked exception.

Which of the following cannot be inherited in Java?

The correct answer is C: Private methods. Private members are not inherited. They remain accessible only within the class they are declared in.

What happens when you attempt to read from a closed InputStream?

The correct answer is B: Throws IOException. Attempting to read from a closed stream throws an IOException with message 'Stream closed', preventing accidental data processing from invalid sources.

What is the purpose of a Predicate functional interface in Java?

The correct answer is C: To test a condition and return a boolean value. Predicate is a functional interface that takes a single input of type T and returns a boolean. It's commonly used for filtering operations in streams.

What is the difference between ResultSet.TYPE_SCROLL_INSENSITIVE and ResultSet.TYPE_SCROLL_SENSITIVE?

The correct answer is A: Insensitive is faster; Sensitive allows concurrent updates visibility. TYPE_SCROLL_INSENSITIVE doesn't reflect concurrent database changes, while TYPE_SCROLL_SENSITIVE may reflect such changes.

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Java Programming
Generics

Java OOP, collections, multithreading

49 Q 10 Topics Take Mock Test

Difficulty: All Easy Medium Hard 31–40 of 49

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.31 Medium Generics

Which statement about generic type parameters is TRUE?

A Type parameters must be uppercase single letters (T, U, V, etc.)

B Type parameters can only be used in class declarations, not in method declarations

C Type parameters can be any valid Java identifier

D Type parameters must match the actual type used at instantiation

Correct Answer: C. Type parameters can be any valid Java identifier

EXPLANATION

While convention uses single uppercase letters, type parameters can be any valid identifier. Statements B and D are also incorrect.

Test

Q.32 Medium Generics

What is the significance of the '&' operator in generic bounds like ''?

A T must extend both A and B (multiple bounds)

B T must extend A or B

C It's a bitwise AND operation

D T extends A with B as an alternative

Correct Answer: A. T must extend both A and B (multiple bounds)

EXPLANATION

Multiple bounds (using &) mean T must satisfy all constraints. This is useful when a type needs to implement multiple interfaces.

Test

Q.33 Medium Generics

Consider the method: public static T getFirst(List list) { return list.get(0); }

How would you call this method for a List?

A String result = Main.getFirst(stringList);

B String result = getFirst(stringList);

C String result = Main.getFirst(stringList);

D Both A and B are correct

Correct Answer: D. Both A and B are correct

EXPLANATION

Type inference in Java allows the compiler to deduce T from the argument type, so both explicit and implicit type specification work.

Test

Q.34 Medium Generics

What is the relationship between raw types and generics in Java?

A Raw types are legacy code that bypasses generic type checking

B Raw types are automatically converted to generic types

C Raw types and generics cannot coexist

D Raw types are more efficient than generics

Correct Answer: A. Raw types are legacy code that bypasses generic type checking

EXPLANATION

Raw types (like 'List' without type parameters) are legacy and should be avoided as they bypass compile-time type safety.

Test

Q.35 Medium Generics

Which generic wildcard usage is INCORRECT?

A List

B List

C Map map;

D List

Correct Answer: D. List

EXPLANATION

Nested wildcards like '? extends ? super T' are not allowed. Wildcards cannot be combined or nested.

Test

Q.36 Medium Generics

In a generic class 'class Box', what constraint is placed on T?

A T must implement the Comparable interface with itself as the type parameter

B T must be a subclass of Comparable

C T must be Comparable with any type

D T is unrestricted and Comparable is optional

Correct Answer: A. T must implement the Comparable interface with itself as the type parameter

EXPLANATION

The bound 'T extends Comparable<T>' ensures T is comparable to itself, enabling type-safe comparison operations.

Test

Q.37 Medium Generics

What does the PECS principle stand for in generics context?

A Producer Extends, Consumer Super

B Parameter Extends, Class Super

C Polymorphic Extends, Constructor Super

D Public Extends, Static Super

Correct Answer: A. Producer Extends, Consumer Super

EXPLANATION

PECS guides when to use upper bounds (? extends) for producers/readers and lower bounds (? super) for consumers/writers.

Test

Q.38 Medium Generics

Which generic declaration would allow storing both String and Integer in the same collection?

A List list = new ArrayList();

B List list = new ArrayList();

C List

D All of the above

Correct Answer: D. All of the above

EXPLANATION

All three allow storing multiple types because they use unbounded or Object-level wildcards, though List<?> is most restrictive for additions.

Test

Q.39 Medium Generics

Which statement correctly uses the lower-bounded wildcard in generics?

A List

B List

C List list = new ArrayList();

D List list = new ArrayList();

Correct Answer: A. List

EXPLANATION

Lower-bounded wildcards (? super T) allow superclasses of T. This assignment is valid because ArrayList<Number> fits '? super Integer'.

Test

Q.40 Medium Generics

In the declaration 'List

A Any Number subclass

B Only Number or its exact subclasses

C Nothing can be added safely (except null)

D Only Integer and Double

Correct Answer: C. Nothing can be added safely (except null)

EXPLANATION

Upper-bounded wildcards (? extends T) are used for reading data. Adding elements is unsafe because the compiler doesn't know the exact type.

Test

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