1Z0-829 Practice Test — Free Oracle Certified Professional Java SE 17 Developer 1Z0-829 Questions with Explanations

In a modular Java application, where does the module declaration file typically reside?

A company uses a multi-release JAR (MR-JAR) that contains classes for Java 9 and Java 11 in `META-INF/versions/9/` and `META-INF/versions/11/` respectively. The application runs on Java 17. Which version of a class that exists in both versioned directories is loaded?

A developer needs to ensure that a class `Shape` cannot be instantiated but can be extended. Which modifier should be used?

Refer to the exhibit. Which statement about this Singleton implementation is correct?

Refer to the exhibit. The exhibit shows a code snippet. What is the output when the variable day is set to Day.WEDNESDAY?

Given: int x=0; do { x++; } while(x<5); How many times does the loop body execute?

When should LinkedList be preferred over ArrayList?

A developer is implementing a custom sort for a list of Employee objects. The Employee class has fields: String name, int age. The list must be sorted first by name (ascending, case-insensitive), then by age (descending). Which Comparator implementation correctly achieves this?

What is the result of executing the following code snippet?

BigDecimal d1 = new BigDecimal("1.00"); BigDecimal d2 = new BigDecimal("1.0"); System.out.println(d1.equals(d2));

A reporting module formats durations for a dashboard. The developer writes:

Duration d = Duration.ofMinutes(90); System.out.println(d.toMinutes() + ":" + d.toMinutesPart());

What is printed?

You are developing a batch processing application that reads records from a CSV file and parses each row into an integer ID. The reading method readNextRecord() returns a String and can throw IOException and NumberFormatException. The method processID(int id) processes the ID. The entire process runs in a for loop over 10,000 records. The requirement is that if any record fails (either due to file read error or parsing), the loop must continue to the next record, but the exception must be logged for later review. Which approach best achieves this requirement?

Consider try-with-resources where resource1 is opened first, then resource2. During closing, both throw exceptions. Which exception is propagated to the caller?

A developer needs to concatenate two Stream<String> into one. Which approach is most idiomatic?

A stream pipeline uses the peek method for debugging. Which statement about peek is correct?

A developer is designing a service that processes multiple files concurrently. To avoid resource leaks, which practice is essential?

An application deserializes objects from a network stream. To protect against deserialization attacks, which approach is most effective in Java 17?

A developer needs a collection that stores unique elements and preserves the order in which they were first inserted. Which implementation should be chosen?

Given: Object obj = "Hello"; String result = switch(obj) { case String s -> "String of length " + s.length(); case Integer i -> "Integer"; default -> "Unknown"; }; What is result?

A company needs to read a large text file (over 2 GB) line by line in a Java application while minimizing memory footprint. Which approach is most efficient?

A developer wants to copy all files from one directory to another, preserving file attributes (e.g., last modified time, permissions). Which NIO.2 method is most appropriate?