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Capgemini · Java
Practice Java questions specifically asked in Capgemini interviews – ideal for online test preparation, technical rounds and final HR discussions.
Questions
20
Tagged for this company + subject
Company
Capgemini
View company-wise questions
Subject
Java
Explore topic-wise practice
Go through each question and its explanation. Use this page for targeted revision just before your Capgemini Java round.
private: class only; default: package; protected: package + subclasses (even cross-package via inheritance); public: everywhere.
For complete preparation, combine this company + subject page with full company-wise practice and subject-wise practice. You can also explore other companies and topics from the links below.
When reusing behavior without inheriting unwanted API; when behavior needs to vary at runtime (strategy pattern); to avoid fragile base-class coupling.
They define stable boundaries—hiding internals (private), exposing minimal extension points (protected), and clear public APIs—reducing coupling and easing evolution.
Collection(List/Set/Queue/Deque) and Map; e.g., ArrayList, HashSet, ArrayDeque, HashMap.
TreeMap is sorted (log N ops, Comparable/Comparator needed); HashMap is unsorted (avg O(1) ops) and only needs equals/hashCode.
Abstract class for shared state/base implementation and ctor control; interface for capability types, multiple inheritance of behavior (default/static).
Constructors tie to class identity. Subclass chains initialization via super(...) call to construct the parent part first.
Mutations can break set/map invariants and lookup; cross-type symmetry/consistency can also be violated.
finally runs after try or catch for cleanup, regardless of normal or exceptional flow. It can be skipped in rare cases like System.exit, JVM crash, or power loss.
Errors like OutOfMemoryError or StackOverflowError signal serious conditions. They are unchecked and not intended for normal recovery logic.
Each thread has its own JVM stack containing frames for method execution.
Literals are interned in the String pool; identical literals share one instance. new String creates a distinct heap object even if an equal literal exists.
Overloading is compile-time (choose method by signature); overriding is runtime (dispatch by actual object).
Finalizers run at GC’s discretion and can cause leaks or latency spikes. Use explicit close patterns or Cleaner for safety and determinism.
An immutable collection cannot change—no element can be added, removed, or mutated through any reference. An unmodifiable view disallows mutations through that view, but the backing collection may still change elsewhere and those changes will appear. Immutability is safer for sharing across threads and for defensive returns; unmodifiable views are lightweight guards around a mutable source.
CompletableFuture supports async pipelines (thenApply, thenCompose), timeouts, combining results, and completion actions without blocking. It works with default or custom executors.
volatile publishes the latest value to all threads and prevents certain re-orderings. It does not make compound updates atomic; use locks or atomics for that.
Use CopyOption flags to control behavior. For example, REPLACE_EXISTING to overwrite, COPY_ATTRIBUTES to preserve metadata, and ATOMIC_MOVE for all-or-nothing moves when supported.
The contract: equal objects must have equal hash codes. Violating it breaks hashing collections, causing lost or duplicate entries. Distinct objects may share a hash code; the map handles collisions.
A functional interface is defined by a single abstract method. @FunctionalInterface is optional and only enforces the rule at compile time. Default and static methods don’t change the SAM count.