Java Instant truncatedTo ChronoUnit MINUTES Result

Handling date, time, text, numeric and boolean values
Answer Correct answer: A — The truncated login time is still before the logout time, so the else block prints "Can't logout".

Given the code fragment: What is the result? - image

  1. Can't logout Correct Answer
  2. Logged out at: 2021-01-12T21:58:00z
  3. A compilation error occurs at line n1.
  4. Logged out at: 2021-01-12T21:58:19.880z

Community Votes

A
100%

100% of anonymous learners picked answer A. Votes are pick records left by other test-takers — they are not the verified answer.

Community Insight

The key trap is confusing 'truncation' with 'rounding'; truncation always rounds down, making the login time earlier than logout time.

This question tests the behavior of Instant.truncatedTo() in Java 8+ datetime API. The correct result is determined by how truncating to minutes affects comparison logic.

Learners often choose D, assuming truncation rounds to the nearest minute or that seconds/nanoseconds are preserved, leading them to believe the times remain distinct enough for a successful logout message.

Community Discussion (6 comments)

nickpati92 👍 1 Selected: A
truncatedTo: Returns a copy of this Instant truncated to the specified unit. Truncating the instant returns a copy of the original with fields smaller than the specified unit set to zero. The fields are calculated on the basis of using a UTC offset as seen in toString. For example, truncating with the MINUTES unit will round down to the nearest minute, setting the seconds and nanoseconds to zero.
Uteman 👍 2
Outputs Can't logout
xplorerpj 👍 1
A is correct
minhdev 👍 3
A is correct: truncatedTo() coverts the logoutTime=LoginTime => else is reached.
james2033 👍 2 Selected: A
package q04; import java.time.Instant; import java.time.temporal.ChronoUnit; public class Q04 { public static void main(String[] args) throws InterruptedException { // Login time: 2021-01-12T21:58:18.817Z Instant loginTime = Instant.now(); Thread.sleep(1000); // Logout time: 2021-01-12T21:58:19.880Z Instant logoutTime = Instant.now(); loginTime = loginTime.truncatedTo(ChronoUnit.MINUTES); // line n1 logoutTime = logoutTime.truncatedTo(ChronoUnit.MINUTES); if (logoutTime.isAfter(loginTime)) { System.out.println("Logged out at: " + logoutTime); } else { System.out.println("Can't logout"); } } } // Result: // Can't logout
Samps 👍 2 Selected: A
A is correct

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Expert Analysis

Why the Answer Is Correct

The code uses loginTime.truncatedTo(ChronoUnit.MINUTES). This method sets all fields smaller than minutes (seconds and nanoseconds) to zero. Since both loginTime and logoutTime occur within the same minute (21:58), truncating loginTime results in 2021-01-12T21:58:00Z. The logoutTime remains 2021-01-12T21:58:19.880Z. The condition if (!loginTime.isBefore(logoutTime)) checks if login is NOT before logout. Since 21:58:00 IS before 21:58:19, the condition is false, and the else block executes, printing "Can't logout".

Why the Other Options Are Wrong

Option B and D represent the actual timestamp values but ignore the program flow logic; they would only print if the condition were true. Option C suggests a compilation error, but truncatedTo is a valid method on Instant accepting ChronoUnit. The syntax is correct.

Community Comment Notes

Most users correctly identified A as the answer. As minhdev noted, "truncatedTo coverts the logoutTime=LoginTime => else is reached," highlighting the logical outcome. James2033 provided a full trace showing the timestamps confirm the 'isBefore' relationship holds true.

Official Reference

https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/time/Instant.html#truncatedTo(java.time.temporal.ChronoUnit)

Exam Strategy

Always trace the value changes step-by-step. When truncatedTo is used, remember it chops off lower units, potentially making two distinct times equal or altering their order relative to expectations.

Frequently Asked Questions

Does truncatedTo round or truncate?

It truncates (chops off) lower units. It does not round to the nearest unit.

Why doesn't it print the logged out message?

Because the login time is strictly before the logout time, the !isBefore check fails, triggering the else block.

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