Basic Java

1. When using Arrays.asList() on an array, what type of List is returned?

A resizable List that can add and remove elements.

A fixed-size List view of the original array.

A deep copy of the original array.

An empty List.

2. Identify the best practices when working with wrapper classes.

Always use equals() when comparing wrapper objects.

Assign null directly to primitive variables.

Use primitive types in tight loops instead of wrapper types.

Ignore NumberFormatException when parsing user input.

3. Which of the following statements about enums are true?

Enums can implement multiple interfaces.

Enums can have their own methods.

Enums can extend other classes.

Enums cannot be serialized.

4. What will this code print?

LocalDate d1 = LocalDate.of(2026, 1, 31);
LocalDate d2 = d1.plusDays(1);
System.out.println(d1);

2026-01-31

2026-02-01

null

It throws an exception.

5. Which of the following statements about Duration, Period, and ChronoUnit are true?

Duration represents a time-based amount (hours/minutes/seconds) and can be used between Instant or LocalDateTime values.

Period represents a calendar-based amount (years/months/days) and can only be used between LocalDate values.

ChronoUnit.DAYS.between(...) returns the total day gap as a single number, unlike Period which breaks it into separate year/month/day pieces.

Period can express an hour/minute-precision gap just as accurately as Duration.

6. Which of the following statements about autoboxing and autounboxing are true?

Autoboxing converts a primitive value into its wrapper object.

Autounboxing converts a wrapper object back into its primitive value.

Autoboxing can only be done manually.

Autounboxing can lead to NullPointerExceptions if the wrapper is null.

7. Which of the following are best practices when working with strings in Java? (Select all that apply)

Use == for string content comparison

Use StringBuilder for concatenating strings in a loop

Always use equals() for string content comparison

Use String for building multi-line text

8. What will this code print? (Assume no setAccessible(true) call is made.)

class Secret {
    private String code = "1234";
}

Field f = Secret.class.getDeclaredField("code");
try {
    Object value = f.get(new Secret());
    System.out.println(value);
} catch (IllegalAccessException e) {
    System.out.println("access denied");
}

1234

access denied

The program crashes with an uncaught exception.

null

9. Which of the following are common mistakes when working with Strings in Java?

Using '==' to compare String content.

Forgetting to assign a String method's return value.

Using StringBuilder for concatenation.

Assuming String.format() truncates numbers.

10. What will the resulting file contain after this code runs?

try (BufferedWriter w = new BufferedWriter(new FileWriter(path.toFile()))) {
    w.write("Line1");
    w.write("Line2");
}

Two separate lines: "Line1" and "Line2"

A single line: "Line1Line2"

Only "Line2"

The code throws an exception because newLine() was never called.

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