Given: import java.util.*; public class Main { static Map<String, String> map = new HashMap<>(); static List<String> keys = new ArrayList<>(List.of("A", "B", "C", "D")); static String[] values =…

The correct answer is D. Map: 4 Keys: 0 Values: 0. Before responding, let me check if any skill applies here. This is a Java exam explanation task - no specific skill covers this. Proceeding directly. --- There's an error in the stated correct answer. The actual output of this program is A: Map: 0 Keys: 0 Values: 0, not D…

Working with Arrays and Collections

Question

Given:
import java.util.*;
public class Main {
static Map<String, String> map = new HashMap<>();
static List<String> keys =
new ArrayList<>(List.of("A", "B", "C", "D"));
static String[] values =
{"one", "two", "three", "four"};
{
for (var i = 0; i < keys.size(); i++) {
map.put(keys.get(i), values[i]);
}
}
public static void main(String[] args) {
keys.clear();
values = new String[0];
System.out.println("Map: " + map.size() +
" Keys: " + keys.size() +
" Values: " + values.length);
}
}
What is the result?

Options

AMap: 0 Keys: 0 Values: 0
BThe compilation fails.
CMap: 4 Keys: 4 Values: 4
DMap: 4 Keys: 0 Values: 0
EMap: 4 Keys: 0 Values: 4

How the community answered

(58 responses)

A
2% (1)
B
9% (5)
C
2% (1)
D
83% (48)
E
5% (3)

Explanation

Before responding, let me check if any skill applies here.

This is a Java exam explanation task - no specific skill covers this. Proceeding directly.

There's an error in the stated correct answer. The actual output of this program is A: Map: 0 Keys: 0 Values: 0, not D.

Here's why: The { } block inside the class (without the static keyword) is an instance initializer, not a static initializer. It only executes when new Main() is called to create an instance - but main() is a static method that never creates any instance. So the loop that populates map never runs, leaving map empty (size 0). Then keys.clear() empties the list and values = new String[0] replaces the array with an empty one, yielding sizes of 0 for all three.

D would be correct only if the block were declared static { ... }, which would run at class-loading time and populate the map before main() clears keys and replaces values. That scenario gives Map: 4, Keys: 0, Values: 0.

Why the other options are wrong as written:

B (compile fails) - code is syntactically valid Java.
C (Map: 4 Keys: 4 Values: 4) - ignores keys.clear() and the values reassignment.
E (Map: 4 Keys: 0 Values: 4) - values = new String[0] replaces the reference with an empty array, so values.length is 0, not 4.

Memory tip: static { } = class-level, runs once at load time. { } alone = instance-level, runs per new. If no instance is created, a bare { } block is dead code.

Bottom line: As the code is written, the answer is A. If your source lists D, the question likely contains a typo - the static keyword was dropped from the initializer block.

Topics

#instance vs static initializers#collection references#Collection.clear()#field state tracking

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