Authentic Oracle Certification Exam 1z0-829 Questions Answers

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 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 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