1Z0-811 Practice Exam 3 — 20 Questions

Question 1

A team is implementing a search algorithm that iterates over an array of integers. The loop should stop as soon as the target value is found. Which loop construct is most appropriate?

Accepted Answer

For loop with break. A for loop with a break statement is the most appropriate construct because it allows iteration over the array with an explicit exit condition the moment the target value is found. The break statement immediately terminates the loop, avoiding unnecessary iterations and clearly expressing the early-exit intent. This is idiomatic Java and matches the requirement to stop as soon as the target is located.

Answer

While loop with a flag variable

Answer

Enhanced for loop with continue

Answer

Do-while loop

Question 2

What is the scope of a variable declared inside a for loop?

Accepted Answer

Only inside the loop block. In Java, a variable declared inside a for loop (including the initialization block or the loop body) has block scope, meaning it is only accessible within the loop block itself. This is defined by the Java Language Specification (JLS §6.10), which states that the scope of a local variable declaration is the rest of the block in which the declaration appears. Once the loop completes, the variable goes out of scope and cannot be referenced.

Answer

Inside the package

Answer

Inside the class

Answer

Inside the entire method

Question 3

Which two statements about the break statement in Java are true?

Accepted Answer

break can be used inside a switch case. The break statement is used inside a switch case to terminate the switch block and prevent fall-through to subsequent cases. Without break, execution would continue into the next case, which is often unintended.

Answer

break can be used without any enclosing loop

Answer

break is used to skip to next iteration

Answer

break exits the current loop iteration

Question 4

Which TWO are valid ways to pass an array to a method in Java?

Accepted Answer

myMethod(new int[]{1,2,3});. Option A is correct because it uses the valid anonymous array syntax new int[]{1,2,3}, which creates an int array and passes it directly as the method argument. Option B is correct because it first declares and initializes an int array with int[] arr = {1,2,3}, then passes the array reference arr to myMethod, which is the standard way to pass an array variable. Option C is incorrect because myMethod(1, 2, 3) passes three separate int arguments, not an array, unless the method specifically uses varargs, which is not stated. Option D is incorrect because the syntax int[] {1,2,3} is invalid; an anonymous array must use new int[]{1,2,3}. Option E is incorrect because Java does not allow specifying both an array size and an initializer list, so new int[5] {1,2,3,4,5} is illegal.

Answer

myMethod(1, 2, 3);

Answer

myMethod(int[] {1,2,3});

Answer

myMethod(new int[5] {1,2,3,4,5});

Question 5

Which access modifier allows a member to be accessed only within the same class?

Accepted Answer

private. The private access modifier restricts a member's visibility to only the class in which it is declared. This is the most restrictive access level in Java, ensuring that no other class—not even subclasses or classes in the same package—can access the member directly. Therefore, private is the correct answer for allowing access only within the same class.

Answer

static

Answer

public

Answer

default (no modifier)

Answer

protected

Question 6

A method declares throws FileNotFoundException and SQLException. Which statement about the caller is true?

Accepted Answer

The caller must handle or declare both exceptions.. In Java, when a method declares checked exceptions (like FileNotFoundException and SQLException) in its throws clause, any caller must either handle each checked exception with a try-catch block or declare them in its own throws clause. The compiler enforces this rule to ensure that checked exceptions are properly accounted for, preventing unhandled checked exceptions from propagating unchecked.

Answer

The caller must catch only FileNotFoundException.

Answer

The caller can declare throws Exception to cover both.

Answer

The caller can ignore both exceptions.

Question 7

A developer needs to handle a specific checked exception, FileNotFoundException, but also wants to catch any other IOException that might occur. Which catch block ordering is correct?

Accepted Answer

catch (FileNotFoundException e) first, then catch (IOException e).. Checked exceptions must be caught in order from most specific to most general. FileNotFoundException is a subclass of IOException, so it must be caught first; otherwise, the more specific catch block would be unreachable and cause a compilation error. This ordering ensures that the developer can handle the specific FileNotFoundException separately while still catching any other IOException in the second block.

Answer

Use a multi-catch: catch (FileNotFoundException | IOException e).

Answer

catch (IOException e) first, then catch (FileNotFoundException e).

Answer

Use a single catch (Exception e).

Question 8

Which TWO statements are true about method overloading in Java?

Accepted Answer

Overloaded methods can have different parameter lists.. Option B is correct because method overloading is defined by methods sharing the same name but differing in their parameter lists, which may vary in the number, types, or order of parameters. Option C is correct because overloaded methods must share the same method name; that shared name is what makes them overloaded rather than simply distinct methods. Option A is incorrect because overloaded methods may have different numbers of parameters, which is one of the valid ways to distinguish them. Option D is incorrect because return type alone cannot distinguish overloaded methods, and overloads are not required to have different return types. Option E is incorrect because methods with different names are not overloaded; they are simply different methods.

Answer

Overloaded methods must have the same number of parameters.

Answer

Overloaded methods must have different return types.

Answer

Overloaded methods can have different names.

Question 9

A developer writes a utility method that accepts a variable number of int arguments and prints their sum. The method is declared as public static int sum(int... values). Which statement correctly describes how this method can be invoked?

Accepted Answer

It can be invoked with zero arguments, one int argument, or multiple int arguments.. A varargs parameter declared as int... values is compiled into an int[] parameter, and the compiler accepts zero or more int arguments at the call site, wrapping them into an array. This makes the method convenient for callers while keeping the implementation type-safe. The other invocation forms described are either overly restrictive or violate Java's type conversion rules.

Answer

It can be invoked with arguments of any numeric type, including double and long, because Java automatically widens them to int.

Answer

It must be invoked with at least one int argument; zero arguments causes a compile-time error.

Answer

It can be invoked only with an explicit int array, such as sum(new int[]{1,2,3}).

Question 10

A developer writes a for loop to process an array of temperatures. The loop must skip any temperature that is below zero and continue processing the remaining temperatures. Which change to the loop body correctly implements this requirement?

Accepted Answer

Insert an if statement that checks for a negative temperature and uses continue; to skip the rest of the current iteration.. The continue statement is designed to skip the remainder of the current loop iteration and move to the next one, which is exactly what is needed to ignore negative temperatures while processing the rest. Using break, return, or System.exit would stop the loop or program prematurely and leave valid temperatures unprocessed.

Answer

Insert an if statement that checks for a negative temperature and uses break; to exit the loop.

Answer

Insert an if statement that checks for a negative temperature and uses return; to leave the method.

Answer

Insert an if statement that checks for a negative temperature and uses System.exit(0); to stop the program.

Question 11

A developer writes the following code:

int x = 5;
switch (x) {
    case 1:
        System.out.print("One ");
    case 5:
        System.out.print("Five ");
    case 10:
        System.out.print("Ten ");
        break;
    default:
        System.out.print("Other ");
}

What is printed?

Accepted Answer

Five Ten. The switch expression x has the value 5, so execution jumps to the matching case 5 and prints "Five ". No break statement follows, so execution falls through into case 10, printing "Ten ". The break after case 10 ends the switch, so default is never reached. The result is the concatenation of both prints: Five Ten.

Answer

Five Ten Other

Answer

Five

Answer

Ten

Question 12

You are tuning a real-time data processing application that reads sensor data from a queue. The system must process each sensor reading, but occasionally a reading is invalid (null) and should be skipped. The loop must run indefinitely until the application is shut down gracefully. The current implementation uses a while(true) loop with a break condition when a shutdown flag is set. However, the loop is consuming excessive CPU because it continuously polls the queue even when no data is available. You need to modify the loop to reduce CPU usage while still processing data efficiently. Which approach should you take?

Accepted Answer

Replace the polling mechanism with a blocking queue that blocks until data is available.. Using a blocking queue (e.g., `BlockingQueue.take()`) causes the consumer thread to block automatically until data becomes available, eliminating busy-waiting and drastically reducing CPU usage. This is the standard pattern for producer-consumer scenarios in Java, as it leverages the underlying `notify`/`wait` mechanism to avoid polling overhead.

Answer

Change the while(true) loop to a for loop that iterates a fixed number of times.

Answer

Add a Thread.sleep(100) inside the loop to reduce polling frequency.

Answer

Use a do-while loop with a Thread.yield() call to give other threads CPU time.

Question 13

Given the method: public static void modify(int[] data) { data = new int[]{10,20}; } What is the output of: int[] vals = {1,2}; modify(vals); System.out.println(vals[0]);

Accepted Answer

1. In Java, when an object reference (including an array) is passed to a method, the reference itself is passed by value. Inside `modify`, the assignment `data = new int[]{10,20}` reassigns the local variable `data` to a new array object, but this does not affect the original reference `vals` in the caller. Therefore, `vals[0]` remains `1`, making option C correct.

Answer

10

Answer

Compilation error

Answer

0

Question 14

Which FOUR statements about the main method are correct? (Choose four.)

Accepted Answer

It must be declared void.. Options A, B, and C are correct because the main method must be declared void, static, and public for the JVM to invoke it as the entry point of a program. Option E is also correct: Java allows overloading of the main method; you can define multiple main methods with different parameter lists, but only the one with the standard signature `public static void main(String[] args)` is used as the program entry point. Option D is incorrect because the main method must not return a value; its return type must be void.

Answer

It must return an int.

Question 15

A developer needs to store a currency value with two decimal places. Which primitive type is most appropriate?

Accepted Answer

double. (double) is the most appropriate primitive type for storing a currency value with two decimal places because double is a 64-bit IEEE 754 floating-point type that can represent fractional values with sufficient precision for typical monetary amounts. While float (32-bit) could also store decimals, double provides higher precision (15-16 significant digits) and is the default type for decimal literals in Java, making it the standard choice for currency calculations in the exam context.

Answer

float

Answer

long

Answer

int

Question 16

A developer is reviewing code that uses assertions. Which two statements about Java assertions are true? (Choose two.)

Accepted Answer

Assertions are enabled at runtime using the -ea command-line option.. Assertions are disabled by default and must be enabled with -ea at runtime. When enabled and an assertion fails, an AssertionError is thrown. They are intended for internal invariant checks, not for validating public method parameters or handling recoverable errors, which should use exceptions.

Answer

Assertions can be used to validate parameters of public methods.

Answer

Assertions are enabled by default when running a Java application.

Answer

Assertions can be used to handle recoverable runtime errors gracefully.

Question 17

A junior developer wrote the following code to compare two strings entered by a user: if (username == "admin") { grantAccess(); } else { denyAccess(); }. The code always denies access even when the user enters 'admin'. What is the most likely cause, and how should the code be fixed?

Accepted Answer

The strings are compared using == which checks reference equality. Use username.equals("admin") instead.. In Java, the == operator compares object references, not the actual content of strings. When comparing two String objects for logical equality, the .equals() method must be used. The code if (username == "admin") checks whether username and the string literal "admin" refer to the same memory location, which is false when username is obtained from user input (e.g., via Scanner or console), even if the characters are identical.

Answer

The input string has leading or trailing spaces. Use username.trim().equals("admin") instead.

Answer

The variable username is null, causing a NullPointerException that is caught and denied access. Add a null check.

Answer

The strings are compared using == which is case-sensitive. Use username.equalsIgnoreCase("admin") instead.

Question 18

What is the output of the following code?

int i = 0;
while (i < 5) {
    if (i == 3) {
        i++;
        continue;
    }
    System.out.print(i + " ");
    i++;
}

Accepted Answer

0 1 2 4. The while loop iterates while i < 5. When i equals 3, the if condition triggers, incrementing i to 4 and then using continue to skip the print statement for that iteration. Thus, 3 is never printed, and the loop prints 0, 1, 2, and then 4 before i becomes 5 and the loop ends.

Answer

0 1 2 3

Answer

0 1 2 4 5

Answer

0 1 2 3 4

Question 19

A developer writes a method that takes a variable number of integer arguments and returns the maximum. Which method signature is correct?

Accepted Answer

public int max(int... numbers). The varargs syntax `int... numbers` allows a method to accept zero or more integer arguments, which are then treated as an array inside the method. This is the standard Java syntax for variable-length argument lists, enabling the developer to pass any number of `int` values and compute the maximum.

Answer

public int max(int[]... numbers)

Answer

public int max(int numbers)

Answer

public int max(int[] numbers)

Question 20

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.