Given the code fragment: int num[] = new int[3]; num[1] = 10; num[2] = 15; List lst = new ArrayList<> (3); lst.add(10); lst.add(15); System.out.println (num); System.out.println (lst); What is the result?

A. a memory address1 in hexadecimal number format a memory address2 in hexadecimal number format

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1Z0-811 · Question #67

Given the code fragment: int num[] = new int[3]; num[1] = 10; num[2] = 15; List<Integer> lst = new ArrayList<> (3); lst.add(10); lst.add(15); System.out.println (num); System.out.println (lst); What…

The correct answer is D. a memory address in hexadecimal number format [10, 15]. Printing num (a plain Java array) invokes the default Object.toString() method, which produces a string like [I@1b6d3586 - a type prefix and hash code rendered as hex - not the array's contents. Printing lst (an ArrayList) produces [10, 15] because ArrayList overrides…

Arrays and Logic

Question

Given the code fragment:
int num[] = new int[3];
num[1] = 10;
num[2] = 15;
List<Integer> lst = new ArrayList<> (3);
lst.add(10);
lst.add(15);
System.out.println (num);
System.out.println (lst);
What is the result?

Options

Aa memory address1 in hexadecimal number format a memory address2 in hexadecimal number format
B10, 15
C0, 10, 15
Da memory address in hexadecimal number format [10, 15]

How the community answered

(18 responses)

A
17% (3)
B
6% (1)
C
6% (1)
D
72% (13)

Explanation

Printing num (a plain Java array) invokes the default Object.toString() method, which produces a string like [I@1b6d3586 - a type prefix and hash code rendered as hex - not the array's contents. Printing lst (an ArrayList) produces [10, 15] because ArrayList overrides toString() to display its elements, making option D the only output that matches both behaviors.

Why the distractors are wrong:

A is wrong because it shows two memory addresses, implying ArrayList also lacks a toString() override - it does not.
B is wrong because it shows only values with no memory address, ignoring how raw arrays print.
C is wrong because it includes 0 (the default value of num[0]), but array contents never print this way regardless - and again ignores the hex-address output.

Memory tip: Think "Arrays are address, Lists are legible." Plain arrays inherit Object's opaque toString(); Java Collections Framework classes (ArrayList, LinkedList, etc.) all override it to show their contents in [...] format. If you need readable array output, use Arrays.toString(num).

Topics

#Array toString()#ArrayList toString()#Object representation#Collections vs Arrays

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