1Z0-811 Practice Test 22 — 15 Questions

Question 1

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. 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

Question 2

What is the value of 10 % 3?

Accepted Answer

1. The modulo operator (%) returns the remainder of integer division. 10 divided by 3 equals 3 with a remainder of 1, so 10 % 3 evaluates to 1. Because both operands are int literals, the result is also an int, not a floating-point value.

Answer

0

Answer

1.0

Answer

3

Question 3

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'.

Answer

Compilation error

Answer

Equal

Answer

Runtime error

Question 4

What is the result of the following code snippet? int x = 5; int y = 2; double z = x / y; System.out.println(z);

Accepted Answer

2.0. In Java, when both operands of the division operator are integers (int), the operation performs integer division, which truncates the fractional part. Here, x / y = 5 / 2 = 2 (integer division), and then the result is implicitly widened to double when assigned to z, producing 2.0.

Answer

3.0

Answer

2

Answer

2.5

Question 5

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.

Question 6

A team is designing a system where a 'Report' class can be generated in different formats (PDF, Excel, HTML). They want to avoid modifying the Report class when adding new formats. Which OOP principle or pattern should they use?

Accepted Answer

Composition. Omposition (often implemented via the Strategy pattern), which allows the Report class to delegate format generation to separate strategy objects. This adheres to the Open/Closed Principle: the Report class is closed for modification but open for extension. Adding a new format only requires creating a new strategy class without altering the Report class. Option B (Composition) is correct. Option A (Method Overloading) is incorrect because it would require adding a new overloaded method for each format in the Report class, violating the goal of not modifying it. Option C (Inheritance) is incorrect because it would create a rigid hierarchy where each format is a subclass of Report, leading to tight coupling and difficulty in adding new formats without modifying existing code. Option D (Singleton) is incorrect because it ensures a single instance, which does not address the need for flexible format generation.

Answer

Method Overloading

Answer

Inheritance

Answer

Singleton

Question 7

A method is declared as 'public void printElements(int... numbers)'. Which invocation will cause a compilation error?

Accepted Answer

printElements({1,2,3});. The syntax `{1,2,3}` is an array initializer that can only be used in a variable declaration or as part of an array creation expression (e.g., `new int[]{1,2,3}`). It cannot be passed directly as an argument to a varargs method. The varargs parameter `int... numbers` expects either a sequence of `int` values or an `int[]` array reference, but not an anonymous array initializer.

Answer

printElements(1, 2, 3);

Answer

printElements();

Answer

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

Question 8

A custom exception class must extend which class to be a checked exception?

Accepted Answer

Exception. In Java, a checked exception is any exception that is a subclass of `Exception` but not a subclass of `RuntimeException`. To create a custom checked exception, your class must extend `Exception` (or a subclass of `Exception` that is itself a checked exception). This forces callers to handle or declare the exception, enforcing compile-time checking.

Answer

Throwable

Answer

Error

Answer

RuntimeException

Question 9

Consider: for(int i=0;i<10;i++) { int x = i; } System.out.println(x); What is the result?

Accepted Answer

Compilation error. The variable `x` is declared inside the `for` loop block, so its scope is limited to that block. Attempting to use `x` outside the loop (in the `System.out.println(x);` statement) causes a compilation error because `x` is not in scope at that point. The Java compiler enforces block-level scoping rules, and any reference to a variable outside its declared block results in a 'cannot find symbol' error.

Answer

9

Answer

10

Answer

0

Question 10

A junior developer wrote a while loop that never terminates. What is the most likely cause?

Accepted Answer

The loop condition is always true. A while loop terminates only when its boolean condition evaluates to false. If the condition is always true, the loop will run indefinitely, causing an infinite loop. In Java, this typically happens when the loop variable is not updated or the condition logic is flawed.

Answer

The loop variable is incremented correctly

Answer

The loop uses a for structure

Answer

The loop body contains a break statement

Question 11

Given the following code:

class A {
    A() { System.out.print("A "); }
}
class B extends A {
    B() { System.out.print("B "); }
}
class C extends B {
    C() { System.out.print("C"); }
    public static void main(String[] args) {
        new C();
    }
}

What is the output when running the main method?

Accepted Answer

A B C. In Java, when an object of a subclass is created, constructors are executed from the topmost superclass down to the subclass. Assuming the exhibit shows class C extends B extends A, with each constructor printing its class name, the output will be A B C.

Answer

B A C

Answer

A C B

Answer

C B A

Question 12

Which loop construct guarantees that the body executes at least once?

Accepted Answer

do-while loop. The do-while loop is a post-test loop, meaning the condition is evaluated after the loop body executes. This guarantees that the body runs at least once, regardless of whether the condition is initially true or false. In contrast, for, while, and enhanced for loops are pre-test loops that check the condition before entering the body, so they may execute zero times.

Answer

enhanced for loop

Answer

for loop

Answer

while loop

Question 13

A logging utility class keeps track of the number of log entries using a static integer variable. The class is instantiated multiple times in the application. How does the count variable behave?

Accepted Answer

All instances share the same count variable. A static variable in Java belongs to the class itself, not to any individual instance. When a class declares a static int count, the JVM allocates exactly one memory slot in the class's method area (or metaspace) that is shared by every instance. Therefore, all instances of the logging utility read and write the same count variable, and increments from one instance are visible to all others.

Answer

Each instance has its own copy of count

Answer

count is reset each time a new instance is created

Answer

count cannot be accessed from static methods

Question 14

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.

Answer

Outer for with inner for, use return

Answer

Outer while with inner for, use continue

Answer

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

Question 15

Which THREE are true about Java constructors?

Accepted Answer

A constructor cannot have a return type. Constructors in Java do not have a return type, not even void. If you attempt to add a return type to a constructor, the compiler treats it as a regular method, not a constructor, which can lead to unexpected behavior. This is a fundamental rule of Java syntax.

Answer

A constructor can be marked final

Answer

A constructor can be abstract