1Z0-811 Practice Test 35 — 15 Questions

Question 1

Refer to the exhibit. A developer runs the command java -version on a system. Which statement about this Java installation is correct?

Accepted Answer

This is a Java Runtime Environment (JRE) installation.. The output shows "Runtime Environment" and no compiler information, indicating a JRE. Version 11.0.12 is Java SE 11 LTS. Option C and D are wrong because the version is 11, not 8 or 17. Option A is incorrect because JDK would include the compiler.

Answer

This is a Java SE 17 installation.

Answer

This is a Java SE 8 installation.

Answer

This is a Java Development Kit (JDK) installation.

Question 2

Which THREE statements are true about the break and continue statements in Java? (Choose three.)

Accepted Answer

A labeled break can be used to exit an outer loop.. A labeled break in Java allows you to specify a label on an outer loop and then use 'break label;' to exit that outer loop directly, not just the innermost loop. This is useful for breaking out of nested loops when a condition is met in an inner loop.

Answer

The continue statement can be used to exit a loop entirely.

Answer

The break statement cannot be used outside a loop.

Question 3

Refer to the exhibit. What is the output?

Accepted Answer

5. The loop iterates i=0,1,2. For i=0: count becomes 1, then 2. For i=1: count becomes 3, continue skips second increment, so count stays 3. For i=2: count becomes 4, then 5. Output is 5.

Answer

3

Answer

6

Answer

4

Question 4

Which of the following is a valid Java identifier?

Accepted Answer

_myVar. (_myVar) is a valid Java identifier because it starts with an underscore, which is permitted by the Java Language Specification. Java identifiers must begin with a letter (A-Z, a-z), dollar sign ($), or underscore (_), and cannot start with a digit or contain hyphens. The underscore is explicitly allowed, making _myVar a legal identifier.

Answer

2variable

Answer

class

Answer

my-var

Question 5

Which of the following correctly describes the effect of the method call 'Arrays.sort(myArray)' on an array of objects that do not implement Comparable?

Accepted Answer

A ClassCastException is thrown at runtime.. When `Arrays.sort(myArray)` is called on an array of objects that do not implement the `Comparable` interface, the method attempts to cast elements to `Comparable` to compare them. Since the objects do not implement `Comparable`, a `ClassCastException` is thrown at runtime. The `Arrays.sort(Object[])` method requires that all elements implement `Comparable`; otherwise, it cannot determine a natural ordering.

Answer

The code does not compile because Arrays.sort requires a Comparator.

Answer

The array is sorted using the natural order of the elements.

Answer

The array is sorted using the order defined by the elements' equals method.

Question 6

A developer writes a catch block that handles multiple exception types that have a subclass relationship. Which of the following is a valid use of the multi-catch feature?

Accepted Answer

catch (IOException e) { ... } catch (SomeOtherUnrelatedException e) { ... }. It demonstrates the proper use of separate catch blocks for unrelated exception types, which is valid. The multi-catch feature (introduced in Java 7) allows catching multiple exception types in a single catch block only if they are not in a parent-child relationship; otherwise, the compiler reports an error due to unreachable code. Since IOException and SomeOtherUnrelatedException are unrelated, separate catch blocks are perfectly valid.

Answer

catch (IOException | FileNotFoundException e) { ... }

Answer

catch (FileNotFoundException | IOException e) { ... }

Answer

catch (IOException e) { ... } catch (FileNotFoundException e) { ... }

Question 7

In a nested loop structure, a developer wants to exit completely from the outer loop when a certain condition is met inside the inner loop. Which approach is correct?

Accepted Answer

Use a labeled break statement (e.g., break outerLabel;).. Java's labeled break statement allows a developer to specify an outer loop label and break out of that loop entirely from within an inner loop. This is the only control flow mechanism designed to exit multiple nested loops at once, as a plain break only exits the innermost loop.

Answer

Use a return statement within the inner loop.

Answer

Use a continue statement with a label.

Answer

Use a break statement inside the inner loop.

Question 8

When using try-with-resources, which interface must the resource implement?

Accepted Answer

AutoCloseable. The try-with-resources statement in Java requires that any resource declared in its parentheses implements the `AutoCloseable` interface (or its subinterface `Closeable`). This interface defines a single `close()` method, which the JVM automatically invokes at the end of the try block, ensuring proper resource management without needing an explicit `finally` block.

Answer

Serializable

Answer

Runnable

Answer

Comparable

Question 9

A new developer writes a method that accepts an array and intends to swap the first and last elements. The code is: public static void swapEnds(int[] arr) { int temp = arr[0]; arr[0] = arr[arr.length-1]; arr[arr.length-1] = temp; } What is a potential issue with this method if the array is empty?

Accepted Answer

It will throw an ArrayIndexOutOfBoundsException.. When the array is empty, `arr.length` is 0, so `arr.length - 1` evaluates to -1. Accessing `arr[-1]` throws an `ArrayIndexOutOfBoundsException` because array indices must be non-negative and less than the array length. The method does not check for an empty array before attempting the swap.

Answer

It will throw a NullPointerException.

Answer

It will produce incorrect result because arr.length-1 is negative.

Answer

It will compile and run correctly.

Question 10

Given: int a = 10; int b = 20; boolean flag = a++ > 10 && ++b > 20; What are the values of a and b after execution?

Accepted Answer

a=11, b=20. The expression `a++ > 10 && ++b > 20` uses short-circuit evaluation. Since `a++` is post-increment, the comparison uses the original value of `a` (10) before incrementing, so `10 > 10` is false. Because the left operand is false, the `&&` operator short-circuits and the right operand `++b > 20` is never evaluated. Therefore, `a` is incremented to 11, but `b` remains 20, making option D correct.

Answer

a=10, b=21

Answer

a=10, b=20

Answer

a=11, b=21

Question 11

Which THREE of the following are valid Java operators?

Accepted Answer

<<. (<<) is correct because it is the Java left shift operator, which shifts the bits of an integer or long value to the left by a specified number of positions, filling with zeros. This is a valid bitwise shift operator in Java, defined in the Java Language Specification (JLS §15.19).

Answer

::

Answer

<==

Question 12

Refer to the exhibit. Which action would best resolve this error without changing the code?

Accepted Answer

Grant read permission on the file.. The error is a FileNotFoundException, which occurs when the file does not exist or cannot be opened. Since the code is correct and the file path is valid, the most likely cause is insufficient permissions. Granting read permission on the file resolves the issue without modifying the code, as it allows the JVM to access the file for reading.

Answer

Compile with -Xlint to get more details.

Answer

Change the file path to a directory that exists.

Answer

Use a try-catch to handle FileNotFoundException.

Question 13

Which loop best suits a scenario where the number of iterations is unknown and depends on user input?

Accepted Answer

while loop. The while loop is best when the number of iterations is unknown and depends on user input because it evaluates a boolean condition before each iteration, allowing the loop to continue as long as the condition remains true. This is ideal for scenarios like reading user input until a sentinel value is entered, where the exact number of iterations cannot be predetermined.

Answer

for loop

Answer

for-each loop

Answer

do-while loop

Question 14

Match each Java collection interface to its characteristics.

Accepted Answer

List: Ordered collection (also known as sequence) that allows duplicate elements.. List is ordered and allows duplicates; Set is unordered and no duplicates; Queue is FIFO order; Map maps keys to values with unique keys. Common confusions include swapping List/Set characteristics or misidentifying Map as a collection of single elements.

Answer

Set: Ordered collection that allows duplicate elements.

Answer

Map: Collection of elements with no order and no duplicates.