1z0-829 Free Practice Test

Given:

What is the result?

1. A. 4
2. B. 2
3. C. 6
4. D. Nothing is printed because of an indefinite loop.
5. E. Compilation fails.
6. F. 5
7. G. A runtime exception is thrown.
8. H. 3

Correct Answer: E
The code will not compile because the variable ??x?? is declared as final and then it is being modified in the switch statement. This is not allowed in Java. A final variable is a variable whose value cannot be changed once it is initialized1. The switch statement tries to assign different values to ??x?? depending on the value of ??y??, which violates the final modifier. The compiler will report an error: The final local variable x cannot be assigned. It must be blank and not using a compound assignment. References: The final Keyword (The Java™ Tutorials > Learning the Java Language > Classes and Objects)

Which statement is true about migration?

1. A. Every module is moved to the module path in a top-down migration.
2. B. Every module is moved to the module path in a bottom-up migration.
3. C. The required modules migrate before the modules that depend on them in a top-down^migration.
4. D. Unnamed modules are automatic modules in a top-down migration.

Correct Answer: B
The answer is B because a bottom-up migration is a strategy for modularizing an existing application by moving its dependencies to the module path one by one, starting from the lowest-level libraries and ending with the application itself. This way, each module can declare its dependencies on other modules using the module-info.java file, and benefit from the features of the Java Platform Module System (JPMS), such as reliable configuration, strong encapsulation, and service loading.
Option A is incorrect because a top-down migration is a strategy for modularizing an existing application by moving it to the module path first, along with its dependencies as automatic modules. Automatic modules are non-modular JAR files that are treated as modules with some limitations, such as not having a module descriptor or a fixed name. A top-down migration allows the application to use the module path without requiring all of its dependencies to be modularized first.
Option C is incorrect because a top-down migration does not require any specific order of migrating modules, as long as the application is moved first and its dependencies are moved as automatic modules. A bottom-up migration, on the other hand, requires the required modules to migrate before the modules that depend on them.
Option D is incorrect because unnamed modules are not automatic modules in any migration strategy. Unnamed modules are modules that do not have a name or a module descriptor, such as classes loaded from the class path or dynamically generated classes. Unnamed modules have unrestricted access to all other modules, but they cannot be accessed by named modules, except through reflection with reduced security checks. References:
✑ Oracle Certified Professional: Java SE 17 Developer
✑ Java SE 17 Developer
✑ OCP Oracle Certified Professional Java SE 17 Developer Study Guide
✑ Migrating to Modules (How and When) - JavaDeploy
✑ Java 9 Modularity: Patterns and Practices for Developing Maintainable
Applications

Which two code fragments compile?
A)

B)

C)

D)

E)

1. A. Option A
2. B. Option B
3. C. Option C
4. D. Option D
5. E. Option E

Correct Answer: BE
The two code fragments that compile are B and E. These are the only ones that use the correct syntax for declaring and initializing a var variable. The var keyword is a reserved type name that allows the compiler to infer the type of the variable based on the initializer expression. However, the var variable must have an initializer, and the initializer must not be null or a lambda expression. Therefore, option A is invalid because it does not have an initializer, option C is invalid because it has a null initializer, and option D is invalid because it has a lambda expression as an initializer. Option B is valid because it has a String initializer, and option E is valid because it has an int initializer. https://docs.oracle.com/en/java/javase/17/language/local-variable-type-inference.html

Given the code fragment:

Which code line n1, obtains the java.io.Console object?
A)

B)

C)

D)

E)

1. A. Option A
2. B. Option B
3. C. Option C
4. D. Option D
5. E. Option E

Correct Answer: A
The code fragment is trying to obtain the java.io.Console object, which is a class that provides methods to access the character-based console device, if any, associated with the current Java virtual machine. The correct way to obtain the Console object is to call the static method Console console() in the java.lang.System class. This method returns the unique Console object associated with the current Java virtual machine, if any. Therefore, option A is correct, as it calls System.console() and assigns it to a Console variable. References:
✑ https://docs.oracle.com/javase/17/docs/api/java.base/java/io/Console.html
✑ https://docs.oracle.com/javase/17/docs/api/java.base/java/lang/System.html#cons ole()
✑ https://education.oracle.com/products/trackp_OCPJSE17
✑ https://mylearn.oracle.com/ou/learning-path/java-se-17-developer/99487

Given:

Which two method invocation execute?

1. A. IFace myclassobj = new Myc (); myclassObj.m3 ();
2. B. Ifnce.m3 ();
3. C. iFace mucloassObj = new Myc (); myClassObj.m4();
4. D. new MyC() .m2 ();
5. E. IFace .,4():
6. F. IFace.m2();

Correct Answer: DE
The code given is an interface and a class that implements the interface. The interface has three methods, m1(), m2(), and m3(). The class has one method, m1(). The only two method invocations that will execute are D and E. D is a call to the m2() method in the class, and E is a call to the m3() method in the interface. References: https://education.oracle.com/products/trackp_OCPJSE17, 3, 4, 5