D286 Java Fundamentals - Set 3 - Part 2

Correct Answer: size()

ArrayList uses the size() method. Arrays use the length field, and Strings use the length() method, a common source of confusion.

Correct Answer: Returns the element at the specified position

get(index) retrieves the element stored at the given zero-based index without modifying the list.

Correct Answer: Replaces the existing value and returns the old one

Map keys are unique, so put() with an existing key replaces the associated value and returns the previous value.

Correct Answer: null

HashMap.get() returns null when the key is not present. getOrDefault() can supply an alternative value instead.

Correct Answer: HashSet

A HashSet automatically rejects duplicates and provides fast membership testing, making it well suited to storing unique values.

Correct Answer: 3

Both operands are integers, so integer division truncates the fractional part, yielding 3.

Correct Answer: 3.3333333333333335

Because 10.0 is a double, the division is performed in floating point, producing a decimal result rather than truncating.

Correct Answer: Truncates the decimal portion, giving 9

Casting a floating-point value to int truncates toward zero rather than rounding, so (int) 9.99 evaluates to 9.

Correct Answer: Math.round()

Math.round() rounds to the nearest integer value. Math.floor() always rounds down and Math.ceil() always rounds up.

Correct Answer: 7

Math.abs() returns the absolute value, converting negative numbers to their positive equivalent.

Correct Answer: 8.0

Math.pow(base, exponent) raises 2 to the power of 3, returning 8.0 as a double.

Correct Answer: A compile error occurs

The compiler requires every code path in a non-void method to return a value, producing a missing return statement error otherwise.

Correct Answer: A copy of the reference to the object

Java is strictly pass-by-value, but for objects the value passed is a copy of the reference. The method can modify the object's state but cannot reassign the caller's variable.

Correct Answer: Yes, because both refer to the same array object

The reference copy points to the same underlying array, so modifications to elements inside the method are visible to the caller.

Correct Answer: A parameter accepting a variable number of arguments

Varargs allows a method to accept zero or more arguments of the given type, which the method receives as an array.

Correct Answer: Limited to the loop itself

A variable declared in the for statement's initializer exists only within the loop and is inaccessible after the loop completes.

Correct Answer: A local variable hiding a field with the same name

Shadowing occurs when a local variable or parameter shares a name with a field, hiding the field within that scope. The this keyword disambiguates.

Correct Answer: Initializing an object with specific values at creation

A parameterized constructor accepts values used to initialize the new object's fields, letting each instance start in a specific, valid state.

Correct Answer: One constructor invoking another constructor in the same class

Calling this(...) as the first statement in a constructor invokes another constructor in the same class, avoiding duplicated initialization logic.

Correct Answer: The super() call itself

An explicit call to super() or this() must be the very first statement in a constructor, ensuring initialization proceeds correctly up the hierarchy.