1Z0-811 Practice Test 19 — 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 TWO statements are true about the 'super' keyword in Java?

Accepted Answer

It can be used to call a superclass method that has been overridden.. Option A is correct because super() invokes the superclass constructor. Option C is correct because super.method() calls an overridden superclass method. Option B is wrong because super cannot access private fields. Option D is wrong because super cannot invoke static methods directly. Option E is wrong because super cannot access private methods.

Answer

It can be used to access private methods of the superclass.

Answer

It can be used to access private fields of the superclass.

Answer

It can be used to invoke a static method of the superclass.

Question 3

Refer to the exhibit. What is the output?

Accepted Answer

Bark
Fetching. Option B is correct: The object is a Dog, so sound() prints "Bark". The cast to Dog is valid, so fetch() prints "Fetching". Option A would occur if sound() were not overridden. Option C and D are incorrect because no exception is thrown.

Answer

Bark
 (then throws ClassCastException)

Answer

Animal sound
 (then throws ClassCastException)

Answer

Animal sound
Fetching

Question 4

Which two statements are true about primitive data types in Java?

Accepted Answer

The long data type can store values from -2^63 to 2^63-1.. Option A and E are correct. The long data type ranges from -2^63 to 2^63-1, and the short data type ranges from -32,768 to 32,767. Option B is false because char stores Unicode characters, not just ASCII. Option C is false because float is not precise for decimal numbers. Option D is false because the boolean data type size is not strictly defined and typically is not a single bit.

Answer

The float data type is 32-bit and can represent decimal numbers precisely.

Answer

The boolean data type has a size of 1 bit.

Answer

The char data type can store only ASCII characters.

Question 5

Refer to the exhibit. Given the code, what is the value printed to the console?

Accepted Answer

18. The correct answer is 18. The expression is evaluated as: a++ uses the value 10 then increments a to 11; --b decrements b to 4 then uses 4; multiplication has higher precedence, so 4 * 2 = 8; then addition 10 + 8 = 18. Option A is correct. Option B (19) would result if a++ was after expression (postfix applied later incorrectly). Option C (20) would result if no precedence (10+8 in wrong order). Option D (21) would result if both increments applied beforehand.

Answer

19

Answer

21

Answer

20

Question 6

Which THREE of the following are key features of the Java programming language?

Accepted Answer

Platform independence through bytecode and JVM. Java is platform independent via bytecode, has automatic garbage collection, and is strongly typed. It does not support multiple inheritance for classes (only interfaces) and does not have pointers.

Answer

Use of pointers for direct memory access

Answer

Support for multiple inheritance of classes

Question 7

What is the result of the expression 10 % 3?

Accepted Answer

1. The modulo operator (%) in Java returns the remainder of the division of the left operand by the right operand. Since 10 divided by 3 equals 3 with a remainder of 1, the expression 10 % 3 evaluates to 1.

Answer

3.33

Answer

0

Answer

3

Question 8

A developer needs to concatenate several string values in a loop. Which approach is most efficient for performance?

Accepted Answer

Using StringBuilder. StringBuilder is the most efficient approach for concatenating strings in a loop because it maintains a mutable sequence of characters, avoiding the creation of intermediate String objects. In contrast, using the '+' operator or String.concat() inside a loop results in the allocation of a new String object for each concatenation, leading to O(n²) time complexity and increased garbage collection overhead.

Answer

Using String.concat()

Answer

Using the '+' operator inside the loop

Answer

Using StringBuffer

Question 9

Which command is used to run a Java application from the command line?

Accepted Answer

java. The `java` command is the correct tool to launch a Java application from the command line. It invokes the Java Virtual Machine (JVM) to load and execute the compiled bytecode contained in `.class` files or a JAR file. Without this command, the application cannot run.

Answer

jar

Answer

javac

Answer

javadoc

Question 10

Which access modifier makes a member visible only within its own class?

Accepted Answer

private. The private access modifier restricts visibility to only the class in which the member is declared. No other class, including subclasses or classes in the same package, can access a private member directly. This is the most restrictive access level in Java.

Answer

public

Answer

default (no modifier)

Answer

protected

Question 11

A developer writes the following code: int x = 5; System.out.println(x++); What is the output?

Accepted Answer

5. The expression `x++` is a post-increment operator, which returns the current value of `x` (5) before incrementing it. Therefore, `System.out.println(x++)` prints 5, and then `x` becomes 6. Option B is correct because the output is the original value of `x`.

Answer

Compilation error

Answer

6

Answer

Runtime exception

Question 12

A team decides to use a single Java source file for a small application. Which statement is true about the file structure?

Accepted Answer

It can contain exactly one public class with the same name as the file.. Option C is correct because in Java, when a source file contains a public class, the file name must exactly match the public class name, including case sensitivity. This is a fundamental rule enforced by the Java compiler to ensure proper class loading and package structure. The file can have at most one public top-level class, and that class name determines the file name.

Answer

It must have a main method to compile.

Answer

It can contain multiple public classes.

Answer

The public class name can differ from the file name.

Question 13

What is the default value of a boolean variable in Java?

Accepted Answer

false. In Java, the default value of a boolean variable (when declared as a class field or instance variable) is 'false'. This is specified by the Java Language Specification (JLS §4.12.5), which defines default values for all primitive types. Unlike local variables, which must be explicitly initialized, instance and static variables receive default values automatically.

Answer

null

Answer

true

Answer

0

Question 14

A developer writes the following code:

int a = 5;
int b = 2;
double result = a / b;
System.out.println(result);

What is the output?

Accepted Answer

2.0. Option B is correct because in Java, when both operands of the division operator are integers (int), the operation performs integer division, which truncates the fractional part. Here, a (5) divided by b (2) yields 2, and then the result is implicitly widened to double when assigned to the variable result, producing 2.0.

Answer

2.5

Answer

Compilation fails

Answer

2

1Z0-811 Practice Test 19 — 15 Questions

Exhibit

1Z0-811 Practice Test 19 — 15 Questions

Exhibit