1Z0-811 Practice Test 16 — 15 Questions

Question 1

What is the output of the following code?
String str1 = "Java";
String str2 = new String("Java");
System.out.println(str1 == str2);

Accepted Answer

false. The == operator compares object references. One string is a literal (stored in the string pool) and the other is created using the 'new' keyword (heap object). They are different references, so the comparison returns false.

Answer

true

Answer

Compilation error

Answer

Java

Question 2

Given: byte b = 10; b = b + 1; What is the result?

Accepted Answer

Compilation error. In Java, arithmetic operations on byte promote the result to int. Assigning an int to a byte without a cast causes a compilation error.

Answer

Runtime exception

Answer

b becomes 10

Answer

b becomes 11

Question 3

Which keyword is used to declare a constant in Java?

Accepted Answer

final. The final keyword declares a variable whose value cannot be changed. const and constant are not used.

Answer

constant

Answer

static

Answer

const

Question 4

Which two of the following are valid ways to check if two String objects contain the same characters? (Assume s1 and s2 are non-null String references.)

Accepted Answer

if (s1.compareTo(s2) == 0) { ... }. The correct ways to compare two String objects for character equality are using the equals() method (option E) or compareTo() method returning 0 (option C). Option A (equalsIgnoreCase) ignores case, so it would treat strings with different cases as equal. Option B (==) compares object references, not content. Option D compares s1 with the interned version of s2; this only works if s1 is also interned, which is not guaranteed, making it unreliable.

Answer

if (s1.equalsIgnoreCase(s2)) { ... }

Answer

if (s1 == s2) { ... }

Answer

if (s1 == s2.intern()) { ... }

Question 5

Given: int x = 3 + 4 * 2; What is x?

Accepted Answer

11. Multiplication has higher precedence than addition: 4 * 2 = 8, then 3 + 8 = 11. Therefore, x is 11, making option A the correct answer.

Answer

11

Answer

24

Answer

14

Question 6

An integer counter variable is incremented in a loop that runs 3 billion times. Initially counter = 0. After the loop, the value is printed. Which code snippet correctly handles potential overflow?

Accepted Answer

long counter = 0; for(long i=0; i<3000000000L; i++) counter++; System.out.println(counter);. Uses a long variable, which can hold the value up to 9e18, avoiding overflow. Options A and B use int and will silently overflow because 3e9 exceeds Integer.MAX_VALUE (2.147e9). Option C uses Math.addExact, which throws an ArithmeticException on overflow; while this detects overflow, the question asks for handling it gracefully, and using a long is the proper approach.

Answer

int counter = 0; for(int i=0; i<3000000000L; i++) counter++; System.out.println(counter);

Answer

int counter = 0; for(int i=0; i<3000000000L; i++) counter += 1; System.out.println(counter);

Answer

int counter = 0; for(int i=0; i<3000000000L; i++) counter = Math.addExact(counter, 1); System.out.println(counter);

Question 7

A developer needs to build a SQL query string by concatenating many parts. Which approach is most efficient for repeated concatenation?

Accepted Answer

Using StringBuilder.append(). StringBuilder.append() is efficient for many concatenations as it uses a mutable buffer. StringBuffer is synchronized and slower. String concatenation with '+' creates many intermediate objects. String.concat() also creates new objects.

Answer

Using StringBuffer.append()

Answer

Using String concatenation with +=

Answer

Using String.concat()

Question 8

Which two of the following are valid ways to create a String object?

Accepted Answer

String s = "Hello";. A string literal, which is a valid way to create a String object. Option D uses the String constructor with a string argument, also valid. Option B assigns an integer literal to a String variable, which is not allowed. Option C attempts to cast an Integer object to String, which causes a compile-time error because Integer is not a subclass of String. Option E uses a char literal ('Hello' is invalid because char literals are single characters) and is not assignable to String.

Answer

String s = 12345;

Answer

String s = (String) new Integer(10);

Answer

String s = 'Hello';

Question 9

A company wants to run existing Java SE application code on an embedded device with limited resources. Which Java edition is designed for such environments?

Accepted Answer

Java ME (Micro Edition). Java ME (Micro Edition) is specifically designed for embedded devices and mobile devices with constrained resources. Option A (Java Card) is for smart cards and very small devices like SIM cards. Option B (Java FX) is a UI framework for rich client applications, not an edition of Java. Option C (Java EE) is for enterprise server applications.

Answer

Java Card

Answer

Java FX

Answer

Java EE (Enterprise Edition)

Question 10

Which TWO statements are true about the Java programming language?

Accepted Answer

It is a strongly-typed language.. Options C and E are correct. Java is a strongly-typed language (C) that provides automatic memory management through garbage collection (E). Option A is wrong because Java is object-oriented, not purely procedural. Option B is wrong because Java does not support direct pointer manipulation; it uses references. Option D is wrong because Java does not allow multiple inheritance of classes; it uses interfaces to achieve a form of multiple inheritance.

Answer

It is a purely procedural language.

Answer

It supports direct pointer manipulation for memory access.

Answer

It allows multiple inheritance of classes.

Question 11

Which THREE are valid components of the Java Virtual Machine (JVM)?

Accepted Answer

Heap memory area. The correct components of the JVM listed here are: Heap memory area (C), Execution engine (D), and Class loader subsystem (E). The Java compiler (B) is part of the JDK, not the JVM. Java source code (A) is input to the compiler, not a JVM component. The class loader loads bytecode into the JVM, the heap stores objects, and the execution engine executes bytecode.

Answer

Java source code (.java files)

Answer

Java compiler (javac)

Question 12

What is the most likely cause of this error?

Accepted Answer

The heap size is insufficient for the objects being created.. OutOfMemoryError: Java heap space indicates the heap is full. Option A (memory leak in native code) would typically cause a different error, such as a native memory error. Option C (stack overflow) would be StackOverflowError. Option D (too many threads) would cause an error like 'unable to create new native thread'.

Answer

There is a memory leak in native code outside the heap.

Answer

There is a stack overflow in the method being called.

Answer

Too many threads are running concurrently.

Question 13

Based on the command, which garbage collector is configured for this application?

Accepted Answer

Garbage-First (G1GC). XX:+UseG1GC explicitly sets the Garbage-First (G1GC) garbage collector. Option A is incorrect; Parallel GC would be enabled with -XX:+UseParallelGC. Option C is incorrect; Serial GC would be enabled with -XX:+UseSerialGC. Option D is incorrect; CMS would be enabled with -XX:+UseConcMarkSweepGC.

Answer

Parallel GC

Answer

Serial GC

Answer

Concurrent Mark Sweep (CMS)

Question 14

A company wants to develop a Java application that can run on Windows, Linux, and macOS without any code changes. Which Java feature makes this possible?

Accepted Answer

Platform Independence via JVM. Java achieves platform independence through the Java Virtual Machine (JVM), which interprets compiled bytecode. Option A is wrong because multithreading is a concurrency feature, not responsible for platform independence. Option C is wrong because garbage collection manages memory but does not enable platform independence. Option D is wrong because object-oriented programming is a paradigm, not responsible for cross-platform execution.

Answer

Multithreading

Answer

Garbage Collection

Answer

Object-Oriented Programming

Question 15

Given the javap output of a class file, which statement is correct about the Java version used to compile it?

Accepted Answer

Compiled with Java 11. The major version number in the javap output is 55, which corresponds to Java 11. Java 8 uses major version 52, Java 9 uses 53, and Java 10 uses 54. Therefore, the class file was compiled with Java 11.

Answer

Compiled with Java 8

Answer

This is a normal class file but does not indicate a specific Java version

Answer

Compiled with Java 9