1z0-829 Java SE 17 Developer Questions and Answers

The code fragment will execute the update statement and set the course fee of the course with ID 1021 to 5000. The executeUpdate method returns an int value that indicates the number of rows affected by the SQL statement. In this case, only one row will be updated, so the result variable will be 1. The if statement will check if the result is greater than 0, which is true, and print “Updated successfully”. Therefore, the output of the code fragment is true. References: https://education.oracle.com/products/trackp_OCPJSE17, https://mylearn.oracle.com/ou/learning-path/java-se-17-developer/99487, https://docs.oracle.com/en/java/javase/17/docs/api/java.sql/java/sql/Statement.html#executeUpdate(java.lang.String)

The answer is D because the code fragment uses the Stream API to create two streams, s1 and s2, and then concatenates them using the concat() method. The resulting stream is then processed in parallel using the parallel() method, and the distinct() method is used to remove duplicate elements. Finally, the forEach() method is used to print the elements of the resulting stream to the console. Since the order of elements in a parallel stream is unpredictable, the output could be any of the options given, but option D is the most likely. References:

• Oracle Certified Professional: Java SE 17 Developer
• Java SE 17 Developer
• OCP Oracle Certified Professional Java SE 17 Developer Study Guide
• Parallelizing Streams

The answer is B and E because the module-info file should include a provides directive and an exports directive to represent the service provider interface. The provides directive declares that the module provides an implementation of a service interface, which is com.transport.vehicle.cars.Car in this case. The with clause specifies the fully qualified name of the service provider class, which is com.transport.vehicle.cars.impl.CarImpl in this case. The exports directive declares that the module exports a package, which is com.transport.vehicle.cars in this case, to make it available to other modules. The package contains the service interface that other modules can use.

Option A is incorrect because requires is not the correct keyword to declare a service provider interface. Requires declares that the module depends on another module, which is not the case here.

Option C is incorrect because it has a typo in the module name. It should be com.transport.vehicle.cars, not cm.transport.vehicle.cars.

Option D is incorrect because it has a typo in the keyword provides. It should be provides, not Provides. It also has a typo in the service interface name. It should be com.transport.vehicle.cars.Car, not com.transport.vehicle.cars.Car impl. It also has an unnecessary to clause, which is used to limit the accessibility of an exported package to specific modules.

Option F is incorrect because it exports the wrong package. It should export com.transport.vehicle.cars, not com.transport.vehicle.cars.impl. The impl package contains the service provider class, which should not be exposed to other modules.

Option G is incorrect because it exports the wrong package. It should export com.transport.vehicle.cars, not com.transport.vehicle. The vehicle package does not contain the service interface or the service provider class. References:

• Oracle Certified Professional: Java SE 17 Developer
• Java SE 17 Developer
• OCP Oracle Certified Professional Java SE 17 Developer Study Guide
• Java Modules - Service Interface Module - GeeksforGeeks
• Java Service Provider Interface | Baeldung

The answer is C because the code fragment uses a different syntax and logic for the reduce operation than the other options. The reduce method in option C takes a single parameter, which is a BinaryOperator that combines two elements of the stream into one. The method returns an Optional, which may or may not contain a value depending on whether the stream is empty or not. The code fragment then adds 5 to the result of the reduce method, regardless of whether it is present or not. This may cause an exception if the Optional is empty, or produce a different value than the other options if the Optional is not empty.

The other options use a different syntax and logic for the reduce operation. They all take two parameters, which are an identity value and a BinaryOperator that combines an element of the stream with an accumulator. The method returns the final accumulator value, which is equal to the identity value if the stream is empty, or the result of applying the BinaryOperator to all elements of the stream otherwise. The code fragments then add 5 to the result of the reduce method, which will always produce a valid value.

For example, suppose listOfNumbers contains [1, 2, 3]. Then, option A will perform the following steps:

• Initialize accumulator to identity value 5
• Apply BinaryOperator Integer::sum to accumulator and first element: 5 + 1 = 6
• Update accumulator to 6
• Apply BinaryOperator Integer::sum to accumulator and second element: 6 + 2 = 8
• Update accumulator to 8
• Apply BinaryOperator Integer::sum to accumulator and third element: 8 + 3 = 11
• Update accumulator to 11
• Return final accumulator value 11
• Add 5 to final accumulator value: 11 + 5 = 16

Option B will perform the same steps as option A, except using a lambda expression instead of a method reference for the BinaryOperator. Option D will perform the same steps as option A, except using parallelStream instead of stream, which may change the order of applying the BinaryOperator but not the final result. Option E will perform the same steps as option A, except using identity value 0 instead of 5.

Option C, however, will perform the following steps:

• Apply BinaryOperator Integer::sum to first and second element: 1 + 2 = 3
• Apply BinaryOperator Integer::sum to previous result and third element: 3 + 3 = 6
• Return Optional containing final result value 6
• Add 5 to Optional value: Optional.of(6) + 5 = Optional.of(11)

As you can see, option C produces a different value than the other options, and also uses a different syntax and logic for the reduce operation. References:

• Oracle Certified Professional: Java SE 17 Developer
• Java SE 17 Developer
• OCP Oracle Certified Professional Java SE 17 Developer Study Guide
• Guide to Stream.reduce()

The answer is C because the code demonstrates the concept of method overloading and type conversion in Java. Method overloading allows different methods to have the same name but different parameters. Type conversion allows values of one data type to be assigned to another data type, either automatically or explicitly. In the code, the class Test has four methods named sum, each with different parameter types: int, float, and double. The main method creates an instance of Test and calls the sum method with different arguments. The compiler will choose the most specific method that matches the arguments, based on the following rules:

• If there is an exact match between the argument types and the parameter types, that method is chosen.
• If there is no exact match, but there is a method with compatible parameter types, that method is chosen. Compatible types are those that can be converted from one to another automatically, such as int to long or float to double.
• If there is more than one method with compatible parameter types, the most specific method is chosen. The most specific method is the one whose parameter types are closest to the argument types in terms of size or precision.

In the code, the following method calls are made:

• test.sum(10, 10.5) -> This matches the sum(int a, float b) method exactly, so it is chosen. The result is 20.5, which is converted to int and printed as 20 (B).
• test.sum(10) -> This does not match any method exactly, but it matches the sum(double a) method with compatible types, as int can be converted to double automatically. The result is 10.0, which is printed as 10 (A).
• test.sum(10.5, 10) -> This does not match any method exactly, but it matches two methods with compatible types: sum(float a, float b) and sum(double a, double b). The latter is more specific, as double is closer to the argument types than float. The result is 20.5, which is printed as 20 (D).

Therefore, the output is B A D. References:

• Oracle Certified Professional: Java SE 17 Developer
• Java SE 17 Developer
• OCP Oracle Certified Professional Java SE 17 Developer Study Guide
• Method Overloading in Java
• Type conversion in Java with Examples
• Java Method Overloading with automatic type conversions

The code fragment is creating a string variable “s” with the value “10_00” and an integer variable “s2” with the value 10. The string “s” is using an underscore as a separator for readability, which is allowed in Java SE 171. The question is asking for two statements that can add 250 to the numeric value of “s” and assign it to an integer variable “res”. The correct answers are A and E because they use the methods parseInt and valueOf of the Integer class to convert the string “s” to an integer. Both methods interpret the string as a signed decimal integer and return the equivalent int or Integer value23. The other options are incorrect because they either use invalid syntax, such as B and C, or they do not convert the string “s” to an integer, such as D and F. References: Binary Literals (The Java™ Tutorials > Learning the Java Language > Numbers and Strings), Integer (Java SE 17 & JDK 17), Integer (Java SE 17 & JDK 17)

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)

The code fragment uses the Collections.binarySearch method to search for the string “e3” in the list. The first search returns the index of the element, which is 2. The second search returns the index of the element, which is 0. The third search returns the index of the element, which is -4. The final result is 2. References: Collections (Java SE 17 & JDK 17) - Oracle

The code fragment is using the Stream API to perform a reduction operation on a list of ElectricProduct objects. The reduction operation consists of three parts: an identity value, an accumulator function, and a combiner function. The identity value is the initial value of the result, which is 0.0 in this case. The accumulator function is a BiFunction that takes two arguments: the current result and the current element of the stream, and returns a new result. In this case, the accumulator function is (a,b) -> a + b.getPrice (), which means that it adds the price of each element to the current result. The combiner function is a BinaryOperator that takes two partial results and combines them into one. In this case, the combiner function is (a,b) -> a + b, which means that it adds the two partial results together.

The code fragment then applies a filter operation on the stream, which returns a new stream that contains only the elements that match the given predicate. The predicate is p -> p.getPrice () > 10, which means that it selects only the elements that have a price greater than 10. The code fragment then applies a map operation on the filtered stream, which returns a new stream that contains the results of applying the given function to each element. The function is p -> p.getName (), which means that it returns the name of each element.

The code fragment then calls the collect method on the mapped stream, which performs a mutable reduction operation on the elements of the stream using a Collector. The Collector is Collectors.joining (“,”), which means that it concatenates the elements of the stream into a single String, separated by commas.

The code fragment then prints out the result of the reduction operation and the result of the collect operation, separated by a new line. The result of the reduction operation is 300.00, which is the sum of the prices of all ElectricProduct objects that have a price greater than 10. The result of the collect operation is CellPhone,ToyCar,Motor,Fan, which is the concatenation of the names of all ElectricProduct objects that have a price greater than 10.

Therefore, the output of the code fragment is:

300.00 CellPhone,ToyCar,Motor,Fan

References: Stream (Java SE 17 & JDK 17) - Oracle, Collectors (Java SE 17 & JDK 17) - Oracle

The answer is B because the code fragment contains a syntax error that prevents it from compiling. The code fragment tries to catch a StockException in line 10, but the catch block does not have a parameter of type StockException. The catch block should have a parameter of type StockException, such as:

catch (StockException e) { // handle the exception }

This is required by the Java syntax for the catch clause, which must have a parameter that is a subclass of Throwable. Without a parameter, the catch block is invalid and causes a compilation error.

Option A is incorrect because the program does not throw a StockException, as it does not compile.

Option C is incorrect because the program does not throw an OutofStockException, as it does not compile.

Option D is incorrect because the program does not throw a ClassCastException, as it does not compile. References:

• Oracle Certified Professional: Java SE 17 Developer
• Java SE 17 Developer
• OCP Oracle Certified Professional Java SE 17 Developer Study Guide
• The try-with-resources Statement (The Java™ Tutorials > Essential Classes > Exceptions)
• The catch Blocks (The Java™ Tutorials > Essential Classes > Exceptions)

The code fragment is using the switch statement with the new Java 17 syntax. The switch statement checks the value of the variable desig and executes the corresponding case statement. In this case, the value of desig is “CTO”, which does not match any of the case labels. Therefore, the default case statement is executed, which prints “Undefined”. The other case statements are not executed, because there is no fall through in the new syntax. Therefore, the output of the code fragment is:

Undefined

The code is defining an enum class called Forecast with three values: SUNNY, CLOUDY, and RAINY. The toString() method is overridden to always return “SNOWY”. In the main method, the ordinal value of SUNNY is printed, which is 0, followed by the value of CLOUDY converted to uppercase, which is “CLOUDY”. However, since the toString() method of Forecast returns “SNOWY” regardless of the actual value, the output will be “0 SNOWY”. References: Enum (Java SE 17 & JDK 17), Enum.EnumDesc (Java SE 17 & JDK 17)