1Z0-811 Practice Test 22 — 15 Questions

Question 1

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. Static variables are shared among all instances of a class. There is only one copy of the variable, regardless of the number of instances.

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 2

Which TWO are characteristics of the Java Runtime Environment (JRE)?

Accepted Answer

It is necessary to run any Java application.. Options D and E are correct. The JRE (Java Runtime Environment) is necessary to run any Java application (D) and it contains the JVM and core class libraries (E). Option A is incorrect because the Java compiler (javac) is part of the JDK, not the JRE. Option B is incorrect because although the JRE is smaller than the JDK, this is a relative comparison and not a defining characteristic of the JRE itself. Option C is incorrect because the debugger is included in the JDK, not the JRE.

Answer

It includes the Java compiler (javac) for compiling source code.

Answer

It is smaller in size compared to the JDK.

Answer

It provides a debugger for troubleshooting code.

Question 3

Which two of the following operators are logical operators in Java? (Choose two.)

Accepted Answer

||. || is the logical OR operator in Java, which returns true if at least one of the two boolean operands is true. Option C is correct because && is the logical AND operator, which returns true only if both boolean operands are true. Both operators perform short-circuit evaluation, meaning the right operand is not evaluated if the result is already determined by the left operand.

Answer

&

Answer

|

Answer

~

Question 4

A developer needs to implement a menu-driven program that repeatedly displays options, reads input, and processes the choice until the user selects 'Exit'. Which loop structure and control flow is most appropriate?

Accepted Answer

do-while loop with switch statement. A do-while loop guarantees at least one iteration, which is ideal for menu-driven programs where the menu must be displayed before any input is processed. The switch statement provides a clean, readable way to handle multiple discrete choices (like menu options) compared to a chain of if-else statements, and it aligns with Java's control flow best practices for such scenarios.

Answer

for loop with break condition and nested if-else

Answer

for(;;) loop with if-else chain

Answer

while(true) loop with if-else chain

Question 5

Which TWO statements correctly describe the Java language? (Choose two.)

Accepted Answer

Java supports object-oriented programming.. Java is fundamentally an object-oriented programming language that supports encapsulation, inheritance, and polymorphism. Java's design revolves around classes and objects, and all code must be written inside a class, making OOP a core principle of the language.

Answer

Java supports multiple inheritance of implementation.

Answer

Java supports operator overloading.

Answer

Java supports multiple inheritance of classes.

Question 6

A company is developing a Java-based inventory management system. The system runs on a single server and processes up to 1000 concurrent requests. The development team has implemented the code using multiple threads to handle requests. Recently, the system has been experiencing intermittent data corruption in the inventory counts. After reviewing the code, the team suspects that the issue is related to thread safety. The team is considering the following solutions: (A) Use the 'synchronized' keyword on all methods that update inventory counts. (B) Use 'volatile' keyword on the inventory count variables. (C) Use 'AtomicInteger' for inventory counts. (D) Increase the number of threads to handle requests faster. Which solution should the team implement to fix the data corruption issue with minimal performance impact?

Accepted Answer

Use 'AtomicInteger' for inventory counts.. AtomicInteger provides thread-safe atomic operations (like incrementAndGet) without requiring synchronization, ensuring consistent inventory counts under concurrent access with minimal performance overhead compared to full method synchronization.

Answer

Increase the number of threads to handle requests faster.

Answer

Use 'volatile' keyword on the inventory count variables.

Answer

Use the 'synchronized' keyword on all methods that update inventory counts.

Question 7

A method 'public static void sort(int[] arr)' sorts the array in place. After calling 'sort(data)', the original array 'data' is changed. Which design issue does this demonstrate?

Accepted Answer

The method should return a new array to avoid side effects.. The method modifies the original array passed as an argument, which is a side effect. In Java, arrays are objects, and when passed to a method, the reference is passed by value, allowing the method to modify the array's contents. To avoid side effects and maintain immutability, the method should return a new sorted array instead of modifying the original.

Answer

The method should use a wrapper class for the array.

Answer

The method should be declared as void to indicate modification.

Answer

The method should use pass-by-value to avoid modification.

Question 8

A developer writes the following code: String s1 = "Hello"; String s2 = "Hello"; System.out.println(s1 == s2); What is the output?

Accepted Answer

true. String literals in Java are interned, meaning both s1 and s2 refer to the same String object in the string constant pool. The == operator compares object references, not content, so since both variables point to the same interned string, the comparison yields true.

Answer

Compilation fails

Answer

false

Answer

Hello

Question 9

Which TWO statements about the enhanced for loop (for-each) are correct?

Accepted Answer

It can iterate over any object that implements the Iterable interface.. The enhanced for loop (for-each) works with any object that implements the Iterable interface, which includes all Collection classes (like ArrayList, HashSet) and arrays. This allows the loop to iterate over elements without needing an explicit iterator or index, relying on the iterator() method provided by the Iterable contract.

Answer

It can be used to modify the elements of an array.

Answer

It can only be used with collections.

Answer

It provides an implicit counter variable.

Question 10

A developer writes: for(int i=0; i<10; i++) { if(i%2==0) continue; System.out.print(i); }. What is the output?

Accepted Answer

13579. The loop iterates from i=0 to i=9. The `continue` statement skips the rest of the loop body when the condition `i%2==0` is true (i.e., when i is even). Therefore, only odd values of i (1, 3, 5, 7, 9) are printed, producing the output '13579'. Option B is correct.

Answer

0123456789

Answer

02468

Answer

123456789

Question 11

Refer to the exhibit. What is the output?

Accepted Answer

true. The expression evaluates to true. Operator precedence: ! highest, then &&, then ||. Given typical values (a=false, b=true), !a=true, then b && !a = true && true = true, then a || (b && !a) = false || true = true. Thus output is true. Option A is incorrect because the expression yields true, not false. Option C and D are incorrect as there is no exception or compilation error.

Answer

false

Answer

NullPointerException

Answer

Compilation error: invalid operator

Question 12

Which operator is used to compare two strings for value equality in Java?

Accepted Answer

equals(). The equals() method in Java's String class compares the actual character sequences of two strings for value equality. Unlike the == operator, which checks reference equality (whether two references point to the same object in memory), equals() performs a lexicographic comparison of the string contents, returning true if and only if both strings have the same length and the same characters in the same order.

Answer

compareTo()

Answer

=

Answer

==

Question 13

In a Java method, a developer needs to skip the current iteration and move to the next when a certain condition is met inside a for loop. Which statement should be used?

Accepted Answer

continue;. The `continue` statement in Java immediately skips the remaining code in the current iteration of a loop and proceeds to the next iteration. This is exactly what the developer needs when a condition is met inside a `for` loop to move to the next cycle without executing further statements in the current iteration.

Answer

return;

Answer

exit;

Answer

break;

Question 14

A program needs to read user input until 'quit' is entered. Which loop ensures that the condition is evaluated after executing the body at least once?

Accepted Answer

do-while loop. The do-while loop is the only loop construct in Java that guarantees the loop body executes at least once before the condition is evaluated. This is because the condition is checked after the body runs, making it ideal for scenarios like reading user input until a sentinel value like 'quit' is entered, where the first input must be processed before checking.

Answer

enhanced for loop

Answer

for loop

Answer

while loop

Question 15

Which method overloading is valid?

Accepted Answer

void print(int a) and void print(String s) {}. Method overloading in Java requires methods to have the same name but different parameter lists (different number, type, or order of parameters). Here, `void print(int a)` and `void print(String s)` have different parameter types (`int` vs `String`), which satisfies the overloading rule. The return type or access modifiers do not affect overloading.

Answer

void print(int a) and void print(int b) {}

Answer

void print(int a) and int print(int a) {}

Answer

void print(int a) and private void print(int a) {}