D286 Java Fundamentals - Set 1 - Part 3

Correct Answer: Providing controlled read and write access to private fields

Getters and setters provide managed access to private fields, allowing validation, computed values, or logging without exposing the field directly.

Correct Answer: The number of characters in the String

String.length() returns the count of characters in the String. Note that arrays use a length field while Strings use a length() method.

Correct Answer: Once created, their character content cannot be changed

String objects cannot be modified after creation. Methods that appear to change a String actually return a new String, leaving the original intact.

Correct Answer: StringBuilder

Repeated String concatenation creates many intermediate objects. StringBuilder modifies an internal buffer, making it far more efficient for building Strings iteratively.

Correct Answer: "ogr"

substring(2, 5) returns characters from index 2 up to but not including index 5. For "programming", that yields "ogr".

Correct Answer: A class that represents a primitive value as an object

Wrapper classes such as Integer, Double, and Boolean represent primitive values as objects, allowing them to be used in collections and generics.

Correct Answer: Automatic conversion between a primitive and its wrapper class

Autoboxing automatically converts a primitive to its wrapper object, and unboxing performs the reverse, letting primitives be used where objects are required.

Correct Answer: Prevents the class from being subclassed

A final class cannot be extended. String is a well-known example, declared final to guarantee its immutability and security properties.

Correct Answer: A namespace grouping related classes and interfaces

A package organizes related classes into a namespace, preventing naming conflicts and providing an access control boundary.

Correct Answer: Makes classes from another package usable by their simple names

The import statement lets code refer to classes from other packages by their simple names rather than fully qualified names. It does not copy any code.