1Z0-811 What is Java — Timed 15 Questions

Question 1

A developer is writing a Java application that processes a large number of transactions. The application must ensure that each transaction is committed only if all steps complete successfully, otherwise the entire transaction should be rolled back. Which Java concept should the developer use to implement this requirement?

Accepted Answer

Exception handling. Option A is correct because exception handling in Java allows the developer to catch runtime failures (e.g., SQLException, IOException) within a try block and, in the catch block, invoke a rollback on the transaction (e.g., Connection.rollback()). If all steps succeed, the transaction is committed via Connection.commit(). This ensures atomicity — the 'all-or-nothing' property required for transaction processing.

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Inheritance

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Multithreading

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Encapsulation

Question 2

A team is designing a Java application that needs to run on different operating systems without modification. Which Java feature makes this possible?

Accepted Answer

The Java Virtual Machine. The Java Virtual Machine (JVM) is the key enabler of Java's 'write once, run anywhere' capability. When you compile Java source code, the Java compiler produces bytecode, which is platform-independent. This bytecode is then executed by the JVM, which is implemented specifically for each operating system (Windows, Linux, macOS, etc.), translating the bytecode into native machine instructions. Therefore, the same compiled .class file can run on any OS that has a compatible JVM, without requiring any modifications to the application code.

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Just-in-time compilation

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Garbage collection

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The Java compiler

Question 3

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

Accepted Answer

Java supports object-oriented programming.. Option C is correct because 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.

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Java supports multiple inheritance of implementation.

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Java supports operator overloading.

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Java supports multiple inheritance of classes.

Question 4

A developer runs the command shown in the exhibit. The developer wants to ensure the application uses the latest available language features. Which action should the developer take?

Accepted Answer

Download and install a newer version of the JDK.. Option A is correct because the latest available language features (e.g., pattern matching, sealed classes, records) are tied to the JDK version. Downloading and installing a newer JDK provides both the compiler (javac) and runtime (JVM) that support those features. Simply upgrading the JVM (Option D) or using -source/-target flags (Option C) does not enable new language syntax in the compiler if the JDK itself is outdated.

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Enable lambda expressions by setting the -enable-lambdas flag.

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Use the -source and -target flags to compile for a newer version.

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Upgrade the JVM to the latest version.

Question 5

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.. Option A is correct because 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.

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Increase the number of threads to handle requests faster.

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Use 'volatile' keyword on the inventory count variables.

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

Question 6

Arrange the steps to compile and run a Java program from the command line in the correct order.

Question 7

Arrange the steps to overload a method in Java in the correct order.

Question 8

Match each Java term to its correct definition.

Question 9

Match each OOP concept to its Java implementation.

Question 10

A developer says Java is platform-independent because of the JVM. Which statement best explains this?

Accepted Answer

Java source code is compiled into bytecode, which runs on the Java Virtual Machine (JVM).. Option B is correct because Java source code is compiled into bytecode, which runs on the JVM, making it platform-independent at the source level. Option A is incorrect because Java does not compile to native code for each platform; it compiles to bytecode. Option C is incorrect because Java uses both a compiler and interpreter/JIT. Option D is incorrect because the JVM itself is platform-specific, but bytecode is not.

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Java source code is compiled directly into native machine code for each platform.

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The JVM is written in platform-independent code, allowing it to run anywhere.

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Java uses an interpreter only, so the source code is interpreted directly on any platform.

Question 11

A company is developing a security-sensitive banking application. Which Java feature most directly enhances security?

Accepted Answer

Bytecode verification. Option B is correct because bytecode verification ensures that code adheres to JVM security constraints, preventing malicious operations. Option A (garbage collection) relates to memory management, not direct security. Option C (multithreading) is a concurrency feature. Option D (platform independence) is about portability, not security.

Answer

Automatic garbage collection

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Platform independence via bytecode

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Built-in multithreading support

Question 12

A team deploys a Java application and observes frequent Full GC pauses. Which garbage collector is designed to minimize pause times?

Accepted Answer

Garbage-First (G1GC) (-XX:+UseG1GC). Option C is correct because G1GC (Garbage-First) is designed to provide predictable pause times and reduce Full GC occurrences. Option A (Parallel) focuses on throughput, not pause times. Option B (CMS) was deprecated and can cause fragmentation. Option D (Serial) is for single-threaded environments and has long pauses.

Answer

Concurrent Mark Sweep (CMS) (-XX:+UseConcMarkSweepGC)

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Serial GC (-XX:+UseSerialGC)

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Parallel GC (-XX:+UseParallelGC)

Question 13

What is the primary role of the Java Development Kit (JDK) compared to the JRE?

Accepted Answer

JDK includes compilers and tools for developing Java applications.. Option A is correct because JDK includes development tools like javac, while JRE only provides runtime environment. Option B is wrong because both JDK and JRE support the same platforms. Option C is wrong because JDK includes JRE, not the other way. Option D is inaccurate because JDK includes debuggers and profilers.

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JDK provides only a debugger and profiler.

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JRE includes the JDK and additional libraries.

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JDK is required to run Java applications, whereas JRE is not.

Question 14

An application is designed with private fields and public getter/setter methods. Which OOP principle does this exemplify?

Accepted Answer

Encapsulation. Option C is correct because encapsulation hides internal state and exposes behavior through methods. Option A (inheritance) is about class hierarchy. Option B (polymorphism) is about multiple forms. Option D (abstraction) is about hiding complexity, but encapsulation specifically involves access control.

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Polymorphism

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Inheritance

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Abstraction

Question 15

In the Java memory model, where are primitive local variables declared inside a method stored?

Accepted Answer

Stack. Option D is correct because primitive local variables are stored on the stack. Option A (heap) stores objects and arrays. Option B (method area) stores class metadata. Option C (native area) is for native method memory.

Answer

Heap

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Native method area

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Method area