100+ Free Java SE 8 Programmer II Practice Questions

Java Class Design

Apply encapsulation, inheritance, and polymorphism; understand virtual method invocation and method hiding for statics; implement singletons (including the enum singleton), immutable classes with defensive copies, and correct equals/hashCode contracts for hash-based collections.

Advanced Java Class Design

Use abstract classes and interfaces (including default and static methods and the diamond-conflict resolution rule), enums with fields and constructors, nested and inner classes with effectively-final capture, and single-abstract-method functional interfaces as lambda targets.

Generics and Collections

Create type-safe collections, apply bounded type parameters and upper/lower wildcards following PECS, leverage generic methods, sort with Comparator chains and Comparable, and use Map, List, Set, Deque, NavigableMap, and method references.

Lambda Built-in Functional Interfaces

Select and compose the built-in interfaces Predicate, Supplier, Consumer, Function, UnaryOperator, BinaryOperator, BiFunction, and their primitive specializations, and chain behavior with andThen, compose, and negate to avoid autoboxing where possible.

Java Stream API

Build lazy pipelines with filter, map, flatMap, peek, sorted, and limit; terminate with reduce, collect, count, findFirst, and findAny; use Optional safely; and apply Collectors such as groupingBy, partitioningBy, toMap, and joining, plus parallel-stream correctness rules.

Exceptions and Assertions

Use try-with-resources (reverse-order closing and suppressed exceptions), multi-catch with its implicitly-final parameter, custom checked and unchecked exceptions, finally control-flow precedence, and assertions enabled with -ea for internal invariants.

Use Java SE 8 Date/Time API

Work with the immutable java.time types LocalDate, LocalTime, LocalDateTime, and ZonedDateTime; distinguish date-based Period from time-based Duration; compute signed spans with ChronoUnit; and format and parse with DateTimeFormatter.

Java I/O Fundamentals

Read and write data with byte streams and character readers/writers, apply buffering for performance, use System.console safely (it can return null), and serialize objects with Serializable while handling transient and static fields.

Java File I/O (NIO.2)

Use the Path and Files APIs to resolve, relativize, normalize, and inspect paths; copy and move files with StandardCopyOption; and lazily stream the file tree and content with Files.walk, Files.find, and Files.lines inside try-with-resources.

Java Concurrency

Start threads correctly with start(); use ExecutorService, Callable, and Future; apply concurrent collections (ConcurrentHashMap, CopyOnWriteArrayList) and atomics; coordinate with CyclicBarrier and CountDownLatch; parallelize with Fork/Join; and reason about volatile visibility and deadlock.

Building Database Applications with JDBC

Obtain connections through auto-registered JDBC 4.0 drivers, run parameterized PreparedStatements to block SQL injection, advance and read ResultSet cursors correctly, and close Connection, Statement, and ResultSet with try-with-resources.

Localization

Build locale-aware applications with Locale and ResourceBundle (including the most-specific-to-base fallback chain) and format numbers and currency per locale with NumberFormat.