1Z0-811 Practice Test 13 — 15 Questions

Question 1

What is the result of the following code? int a = 8; int b = 3; System.out.println(a >> 1);

Accepted Answer

4. The right shift operator `>>` shifts the bits of the integer `a` (which is 8, binary `1000`) to the right by 1 position. This discards the least significant bit and fills the most significant bit with the sign bit (0 for positive numbers), resulting in binary `0100`, which is decimal 4. Therefore, `System.out.println(a >> 1)` prints 4.

Answer

2

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3

Answer

16

Question 2

Which THREE are benefits of using inheritance?

Accepted Answer

Code reuse. Inheritance allows a subclass to reuse fields and methods from a superclass without rewriting them. This directly reduces code duplication and promotes maintainability in Java.

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Improved security

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Reduces memory usage

Question 3

A banking application stores daily transaction amounts in an array. Which declaration correctly creates an array of 31 double values?

Accepted Answer

double[] transactions = new double[31];. It uses the proper syntax to declare an array of double values and initializes it with a size of 31, which allocates memory for 31 double elements, each defaulting to 0.0. In Java, the array size must be specified when using the 'new' keyword, and the index range is 0 to 30, accommodating exactly 31 daily transaction amounts.

Answer

double transactions[] = new double[30];

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int[] transactions = new int[31];

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double[] transactions = new double[];

Question 4

Which TWO statements are true about interfaces in Java?

Accepted Answer

Interfaces can contain private methods.. Since Java 9, interfaces can contain private methods to share common code between default methods or static methods within the interface, without exposing that logic to implementing classes. Option D is correct because all variables declared in an interface are implicitly public, static, and final, meaning they are constants that cannot be changed once assigned.

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Interfaces can be instantiated.

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Interfaces can contain constructors.

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Interfaces cannot have default methods.

Question 5

A company develops a payroll system in Java with a hierarchy: Employee, Manager (extends Employee), and Director (extends Manager). Each class overrides a method getDetails() that returns a string with employee information. Employee's getDetails() returns name and ID. Manager's getDetails() adds department. Director's getDetails() adds division. The system uses a single method printDetails(Employee e) that calls e.getDetails(). After a recent deployment, the system prints only the name and ID for all employees, even for managers and directors. The code review reveals that Employee's getDetails() is declared with default (package-private) access, while the overridden versions in Manager and Director are public. The printDetails method and the Manager/Director classes are in different packages. What is the most likely cause and the correct solution?

Accepted Answer

Change the access modifier of getDetails() in Employee to public (or protected).. In Java, a default-access method is not visible to subclasses in different packages, so Manager and Director cannot override it; their getDetails() methods are new methods, not overriding Employee's. Making Employee's getDetails() public (or protected) allows proper overriding and polymorphic behavior. Option B is wrong because it bypasses polymorphism. Option C is wrong because @Override only helps catch errors, but the access issue remains. Option D is wrong because making the method final would prevent overriding entirely.

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Modify printDetails() to accept Manager or Director objects instead of Employee.

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Add @Override annotation to the overridden methods in Manager and Director.

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Declare getDetails() in Employee as final to ensure consistent behavior.

Question 6

Which of the following exceptions is a checked exception?

Accepted Answer

IOException. IOException is a checked exception in Java, meaning it must be either caught or declared in the method signature using a try-catch block or throws clause. Checked exceptions are subclasses of Exception (excluding RuntimeException and its subclasses), and IOException directly extends Exception, making it subject to compile-time checking.

Answer

ArrayIndexOutOfBoundsException

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ArithmeticException

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NullPointerException

Question 7

A developer writes the following code to compare two strings:
String s1 = "Java";
String s2 = new String("Java");
if (s1 == s2) { System.out.println("Equal"); } else { System.out.println("Not equal"); }
What is the output?

Accepted Answer

Not equal. The == operator compares object references, not the actual string content. Variable s1 refers to a string literal from the string pool, while s2 is a new String object created on the heap, so they are different objects and the comparison returns false, printing 'Not equal'.

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Compilation error

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Equal

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Runtime error

Question 8

What is the result of the following code? String s1 = "Hello"; String s2 = " World"; String s3 = s1 + s2; System.out.println(s3);

Accepted Answer

Hello World. The + operator performs string concatenation in Java. s1 + s2 combines "Hello" and " World" to produce "Hello World", which is then printed. The space is part of s2, so the output includes it.

Answer

HelloWorld

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Hello World

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Compilation error

Question 9

In a login system, the authentication method receives an array of user roles as a String[] and checks if a specific role is present. The array may be large (thousands of roles), and the method is called frequently for each user request. Performance is critical. The array is static and does not change after initialization. Which approach is most efficient for repeated checks?

Accepted Answer

Convert the array to a HashSet once and reuse it for lookups.. Converting the array to a HashSet once provides O(1) average-time complexity for subsequent contains() checks, which is far more efficient than O(n) linear search or O(log n) binary search when the method is called frequently on a static array. The HashSet leverages hash codes for direct bucket lookup, making it ideal for repeated membership tests on large, unchanging data sets.

Answer

Use a for loop to iterate and compare each string.

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Sort the array and use Arrays.binarySearch().

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Use a List and the contains() method.

Question 10

Consider the following code:

int[] arr = new int[5];
for (int i = 0; i <= arr.length; i++) {
    arr[i] = i;
}
System.out.println(arr[0]);

What is the result?

Accepted Answer

An ArrayIndexOutOfBoundsException is thrown.. The loop condition `i <= arr.length` causes `i` to iterate from 0 to 5 inclusive. Since `arr` has indices 0 through 4, accessing `arr[5]` throws an `ArrayIndexOutOfBoundsException`. The exception occurs before `arr[0]` can be printed.

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0

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5

Answer

4

Question 11

Which of the following is the best practice for resource management in Java?

Accepted Answer

Use try-with-resources statement.. The try-with-resources statement (introduced in Java 7) automatically closes each resource declared in its header when the block exits, whether normally or due to an exception. This eliminates the need for explicit cleanup code and ensures that resources implementing `AutoCloseable` are closed reliably, preventing resource leaks.

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Close resources in a finally block without null checks.

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Rely on garbage collection to close resources.

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Use a try-catch block and close resources in the catch block.

Question 12

A developer needs to iterate over a 2D array row by row and exit early if a specific value is found in any cell. Which nested loop structure with control statements is most efficient?

Accepted Answer

Outer for with inner for, use labeled break. A labeled break allows the developer to exit both the inner and outer loops immediately when the target value is found. This is the most efficient approach for a row-by-row search in a 2D array, as it avoids unnecessary iterations after the value is located. Using a labeled break provides precise control over nested loop termination without requiring additional flags or method extraction.

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Outer for with inner for, use return

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Outer while with inner for, use continue

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Outer do-while with inner while, use break without label

Question 13

Consider a Java application that throws a NullPointerException deep inside a library method. The stack trace does not include the caller's line numbers because the library was compiled without debug information. Which approach would best help identify the root cause?

Accepted Answer

Recompile the library with -g flag and redeploy.. Recompiling the library with the `-g` flag includes debug information (such as line numbers and local variable names) in the class files. This allows the JVM to produce a stack trace with precise line numbers, enabling you to trace the NullPointerException back to the exact source line in the library code, even though the library was originally compiled without debug info.

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Use a debugger to set breakpoints in the library.

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Use logging statements in the application code before and after the call.

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Add a try-catch around the library call and print the stack trace.

Question 14

Which THREE are primitive data types in Java? (Choose three.)

Accepted Answer

int. `int` is a primitive data type in Java that stores 32-bit signed integer values. Primitive types are predefined by the language and are not objects, meaning they are stored directly on the stack for efficiency.

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String

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Object

Question 15

Arrange the steps to define a class with a main method in Java in the correct order.

Accepted Answer

Step 1: Declare the class, Step 2: Define the main method, Step 3: Add other members, Step 4: Write code in main, Step 5: Compile and run. First declare the class, then define the main method, add other members, write code in main, and finally compile and run.

Answer

Step 1: Declare the class, Step 2: Add other members, Step 3: Define the main method, Step 4: Write code in main, Step 5: Compile and run

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Step 1: Define the main method, Step 2: Declare the class, Step 3: Add other members, Step 4: Write code in main, Step 5: Compile and run

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Step 1: Declare the class, Step 2: Write code in main, Step 3: Define the main method, Step 4: Add other members, Step 5: Compile and run