Pass the Oracle Java SE 1z0-829 Questions and answers with CertsForce

The code snippet is an example of Java SE 17 code. The code is checking if the object is an instance of class C and if it is, it will print “mC”. If it is not an instance of class C, it will print “mA”. In this case, the object is not an instance of class C, so the output will be “mA”. References: Pattern Matching for instanceof - Oracle Help Center

The answer is E because the code fragment contains several syntax errors that prevent it from compiling. Some of the errors are:

The enum declaration is missing a semicolon after the list of constants.

The enum constants are not capitalized, which violates the Java naming convention for enums.

The switch expression is missing parentheses around the variable name.

The case labels are missing colons after the enum constants.

The default label is missing a break statement, which causes a fall-through to the next case.

The println statement is missing a closing parenthesis and a semicolon.

A possible corrected version of the code fragment is:

enum Vehicle { BICYCLE, CAR, MOTORCYCLE, TRUCK; } public class Test { public static void main(String[] args) { Vehicle v = Vehicle.BICYCLE; switch (v) { case BICYCLE: System.out.print(“1”); break; case CAR: System.out.print(“3”); break; case MOTORCYCLE: System.out.print(“1”); break; case TRUCK: System.out.print(“2”); break; default: System.out.print(“0”); break; } System.out.println(); } }

This would print 1 as the output. References:

Oracle Certified Professional: Java SE 17 Developer

Java SE 17 Developer

OCP Oracle Certified Professional Java SE 17 Developer Study Guide

Enum Types

The switch Statement

The answer is D because the code fragment reads the content of the in.txt file and writes it to the out.txt file. The content of the in.txt file is “23456789”. The code fragment uses a char array buffer of size 8 to read the content of the in.txt file. The while loop reads the content of the in.txt file and writes it to the out.txt file until the end of the file is reached. Therefore, the content of the out.txt file will be “0123456789”.

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

A module path is a sequence of directories that contain modules or JAR files. A named module is a module that has a name and a module descriptor (module-info.class) that declares its dependencies and exports. An automatic module is a module that does not have a module descriptor, but is derived from the name and contents of a JAR file. Both named and automatic modules can be placed on the module path, and they can be resolved by the Java runtime. An unnamed module is a special module that contains all the classes that are not in any other module, such as those on the class path. An unnamed module is not on the module path, but it can read all other modules.

The code fragment is using the stream methods allMatch, anyMatch, noneMatch, and findFirst on a list of strings called specialDays. These methods are used to perform matching operations on the elements of a stream, such as checking if all, any, or none of the elements satisfy a given predicate, or finding the first element that matches a predicate1. The predicate in this case is that the string equals “Labour” or “Halloween”. The output will be:

False: because not all of the elements in specialDays are equal to “Labour” or “Halloween”.

true: because at least one of the elements in specialDays is equal to “Labour” or “Halloween”.

true: because none of the elements in specialDays are equal to both “Labour” and “Halloween”.

Optional[NewYear]: because the first element in specialDays that matches the predicate is “NewYear”, and the findFirst method returns an Optional object that may or may not contain a non-null value2.

References: Stream (Java SE 17 & JDK 17), Optional (Java SE 17 & JDK 17)

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 answer is A because the code fragment uses the ZoneId and ZonedDateTime classes to create two date-time objects with the same local date-time but different zone offsets. The ZoneId class represents a time-zone ID, such as America/Chicago, and the ZonedDateTime class represents a date-time with a time-zone in the ISO-8601 calendar system. The code fragment creates two ZonedDateTime objects with the same local date-time of 2021-11-07T01:30, but different zone IDs of America/Chicago and UTC. The code fragment then compares the two objects using the equals and isEqual methods.

The equals method compares the state of two objects for equality. In this case, it compares the local date-time, zone offset, and zone ID of the two ZonedDateTime objects. Since the zone offsets and zone IDs are different, the equals method returns false.

The isEqual method compares the instant of two temporal objects for equality. In this case, it compares the instant of the two ZonedDateTime objects, which is derived from the local date-time and zone offset. Since DST in Chicago ended on November 7th at 2 AM in 2021, the local date-time of 2021-11-07T01:30 in America/Chicago corresponds to the same instant as 2021-11-07T06:30 in UTC. Therefore, the isEqual method returns true.

Hence, the output is true false. References:

Oracle Certified Professional: Java SE 17 Developer

Java SE 17 Developer

OCP Oracle Certified Professional Java SE 17 Developer Study Guide

ZoneId (Java Platform SE 8 )

ZonedDateTime (Java Platform SE 8 )

Time Zone & Clock Changes in Chicago, Illinois, USA

Daylight Saving Time Changes 2023 in Chicago, USA

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 compares four pairs of strings using the equals() and intern() methods. The equals() method compares the content of two strings, while the intern() method returns a canonical representation of a string, which means that it returns a reference to an existing string with the same content in the string pool. The string pool is a memory area where strings are stored and reused to save space and improve performance. The results of the comparisons are as follows:

s1.equals(s2): This returns true because both s1 and s2 have the same content, “Hello Java 17”.

s1 == s2: This returns false because s1 and s2 are different objects with different references, even though they have the same content. The == operator compares the references of two objects, not their content.

s1.intern() == s2.intern(): This returns true because both s1.intern() and s2.intern() return a reference to the same string object in the string pool, which has the content “Hello Java 17”. The intern() method ensures that there is only one copy of each distinct string value in the string pool.

“Hello Java 17” == s2: This returns false because “Hello Java 17” is a string literal, which is automatically interned and stored in the string pool, while s2 is a string object created with the new operator, which is not interned by default and stored in the heap. Therefore, they have different references and are not equal using the == operator.

References: String (Java SE 17 & JDK 17) - Oracle