Java Interview Questions

Core Java

What is JDK & JVM?
- JDK = JRE + Dev Tools
- JRE = JVM + rt lib
What is a JIT compilation? *
what are OOPs features? *
- Abstaction, Encapsulation, Inheritance, Polymarphsm ( AEIP like AEIOU)
What is abstraction?
What is Data hiding?
How does class loading work?
What is a constructor?
What is final?
What is static?
- static means class-level, belogns to class, not to object
What is abstract?
Why it is not allowed to mark a class static? *
- static means class-level
- Top-level class is already class-level, So static is meaningless
- ✔ Only nested (inner) classes can be static
Why Strings are immutable in Java? *
String Vs StringBuffer Vs StringBuilder?

What is String Pool? How it works? ***

How many objects will get created for the below code?

 String s1 = "hello";
 String s2 = new String("world");

How many objects?
```
String s2 = new String("world");
```

How to make Heap String object to point to pool object?

using intern() method.
The intern() method moves the string to the string pool (if not already present) and returns a reference to the pooled instance.

   public class StringInternExample {
   public static void main(String[] args) {
       String heapString = new String("Hello"); // Created in heap memory
       String poolString = heapString.intern(); // Moved to string pool

       String literalString = "Hello"; // Already in the string pool

       System.out.println(poolString == literalString); // true, both refer to the same object in the string pool
           }
   }

What will be the output? Why

  String s1 = "hello";
  String s2 = new String("hello");
  String s3 = "hello";
  System.out.println(s1==s2);
  System.out.println(s1==s3);
  String s4 = s2.intern();
  System.out.println(s1==s4);

Whay is wrpper pool? How it works? ***

it is same like string pool but wrapper classes
it stores/creates obejcts in wrpper pool for Wrapper objects
it creates obejcts only if the wrapper object is in byte range ie -128 to 127
- for char 0 to 127 & for bool true / false
evey wrapper class has it’s own pool

Guess the output?

  Integer i1 = 127;
  Integer i2 = new Integer(127);
  Integer i3 = Integer.valueOf(127); // like string.intern()
  Integer i4 = 127;


  System.out.println(i1 == i2);
  System.out.println(i1 == i3);
  System.out.println(i1 == i4);
  System.out.println("----------");

hashCode() vs System.identityHashCode() vs Object.hashCode()
- Object.hashCode()
  - this returns hashcode based on memory address
  - this won’t consider object state / contents
- System.identityHashCode()
  - this internally calls Object.hashCode(), so returns hashcode based on memory address
- hashCode()
  - this methods exists in Object class, can be overriden
  - Generally, we’ll override this, based on the object state
    - such a way, obejcts with some state should retrun same hascode
  - if we won’t override..then internally it calls Object.hashCode()
How to make an immutable class? *
How many ways we can create a object in java? *
- new
- literal eg: ` String s = “abc”; `
- clone()
- reflection
Cloning? Shallow Copy Vs Deep Copy?
- for deep copy / or custom clone - implement Clonnable & override clone
Can we override static menthods? If not why *
Abstract Class Vs Interface?
Polymorphism?
Inheritance?
Overloading Vs Overriding? or Static Polymorphism Vs Runtime Polymorphism? *
- which is fast?
can we change the return type in override method in child class? *
- Yes, but only Covariant return type (same or subclass of parent return type)

can we change the throwing calls type in override method in child class? *

  // in Parent
  method() throws Excepion

  // in child
  method() throws IllegalArgumentException

What is Diamond Problem in inheritance in Java?
Why multiple inheritance is not supported?
- to prevent ambiguity
Why we should not apply private & abstract together? *
Why we should not apply static & abstract together? *
How to execute a piece of code before the main method? *
- Static Block
What is the order of execution of the following:- *
- constructor, initializers, static initializers, parent constructor, parent initializers, parent static initializers, main method?
- A:- Parent static → Child static → main() → Parent init → Parent constructor → Child init → Child constructor
What is an exception? Give a few examples. When will they occur?
Checked Exceptions Vs Un-Checked Exceptions? *
Thow vs throws?
What
- Is catch block mandatory?
- Is finally block mandatory?
final vs finally vs finalize
what are default methods? *
- A:- instance methods like ( but not, they can’t access instnace variables )
- can we declare default methods in abstract calss?
  - No
- can we override default methods?
  - Yes
- if default method is instance method, can it access instance variable
can we declare instance variables in interface?
- No
What are Collections in Java? Give a few examples, that you used.
- List Vs Set? [ LinkedList vs HashSet ]
- TreeSet Vs HashSet?
- what is Map?
- How HashSet ( HashMap ) works? *
- Note: HashSet internaly uses hashMap
- ArrayList vs LinkedList?
- When LinkedList are better over ArrayList? ***
- HashMap vs ConcurrentHashMap *
- How ConcurrentHashMap works? *
  - thread-safe, faster
  - Uses bucket-level locking
  - Multiple threads access safely
  - No full map lock
- Stack Vs Queue?
Why do we need to override hashCode?
Do we need to override both hashCode and equals? if we are using HashSet to store our object? *
- Yes, hashCode to find the bucket & equals is to check equality check
Can we use Object as a key in HashMap? [ eg: Employee class object ]? ***
- Yes, we can use. But we should use immutable class, else it’ll lead to hash collision
Hash Collision?
Can we add two objects with the same data/states in HashSet/HashMap? Will it allow all? What is the count?
- Depends on the hashcode implementation,
- so if not implemented, it’ll allow duplicates, bcz it compares the address
  - default hashcode return the address of the object
Can we delete/modify an element from a list/collection while iterating using each loop? If not why? *
How to iterate over the Map?
HashMap vs LinkedHashMap vs TreeMap?
- HashMap → no order, fastest
- LinkedHashMap → insertion order maintained
- TreeMap → sorted order (ascending)
HashMap vs SynchronizedMap vs ConcurrentHashMap? **
- HashMap → not thread-safe
- SynchronizedMap → thread-safe (full lock, slow)
- ConcurrentHashMap → thread-safe (bucket-level lock, fast)
HashMap Vs HashTable?
- HashMap → not thread-safe, allows 1 null key : slower
- Hashtable → thread-safe, NO null key/value : faster
does Treemap allows null key
- TreeMap does NOT allow null keys
- Uses compareTo() / Comparator → Null cannot be compared → NullPointerException
Comparable vs Comparator? ***
Can add any User/class without comparable implementation in TreeMap
- we CANNOT add custom objects to TreeMap without Comparable or Comparator
Generics? *
- Allows type-safe code
- Compile-time checking, No casting, Clean code
- Benifits: Avoids ClassCastException → Reusable classes & methods
- Type safety + no casting ✔️
What is type erasure?
- Generic info removed at runtime
<T> vs <?> difference?
- <T> = type parameter
- <?> = unknown type
Bounded generics (<? extends T>, <? super T>) ( Lower bounded, Upper bounded)

<? extends T> vs <? super T> ***

<? extends T> : Accepts T or its child (read-only)
<? super T> : Accepts T or its parent (write-safe)

class Animal {}
class Dog extends Animal {}

//
List<Dog> dogs = new ArrayList<>();
List<? extends Animal> list = dogs; // <? extends T> (Read-only)

Animal a = list.get(0); // allowed, type safe
list.add(new Dog());    // ❌ NOT allowed


//
List<Animal> animals = new ArrayList<>();
List<? super Dog> list = animals; // <? super T> (Write-safe)

list.add(new Dog());   // allowed ( write)
Object obj = list.get(0); // only Object, Cannot read as Dog

Can we use primitive types in generics?
- No, use Wrapper classes
Generic class vs generic method?
- Class: type at class level
- Method: type at method level
Why arrays are covariant but generics are not?
Can we create generic exception class?
- NO
Difference between List<Object> & List<?>
- Object: accepts all
- ?: read-only i.e ? extends Object
Why generics introduced in Java?
- Type safety + no casting ✔️
Garbage collection? Types of Garbage collections? How do they work? *
- Memory Management
- types
  1. Serial GC → Single thread → Small apps
1. Parallel GC → Multi-threaded → High throughput
2. CMS GC → Low pause time
3. G1 GC (Garbage First) → Region-based → Default (Java 9+)
How GC works
1. Mark reachable objects
2. Sweep unused objects
3. Compact memory
what is Region-based GC
- Meaning:
  - Heap is divided into small fixed regions
  - instead of Young/Old generations.
- Used in:G1 GC
- How it works:
- Each region can be young / old / free
- GC collects only required regions
- Predictable pause time
Benefit:
- Better memory utilization
- Low pause time
Region-based GC = GC works on small heap regions instead of whole heap ✔️
what are new improvements in GC after java8
1. G1 GC became default (Java 9) → Region-based → Predictable pause time
2. ZGC (Java 11+) → Ultra-low pause (<10ms) → Scalable (TB heap)
3. Shenandoah GC → Low latency → Concurrent compaction
4. Epsilon GC → No GC (testing, performance)
5. Better heap management → Improved compaction → Less fragmentation
6. Improved concurrent GC → Less stop-the-world → Better responsiveness
Post Java8 → Low latency + scalable + concurrent GCs ✔️
When the static variables are available for garbage collection? *
How to make object available for garbage collection? *
- de-reference assign to null
- System.gc()
What is volatile? *
- Ensures visibility of changes across threads
- Prevents cache inconsistency
- volatile = latest value always visible to all threads
What is transient? *
- Variable not serialized, Skipped during serialization
What is serialization( deserialization)? *
what is externalization?
In the parent, serialization is implemented but not in the child. Will it work or throws an error? [ Vice-Versa]
- Case 1: Parent implements Serializable, Child does NOT
  - Works fine: Child is automatically serializable
- Case 2: Child implements Serializable, Parent does NOT
  - Works BUT:
    - Parent must have no-arg constructor
    - Parent data will NOT be serialized
- Parent serializable → Child auto serializable
- Child serializable → Parent needs default constructor ✔️ else Exception
Can we overload the main method? *
What are all the optional modifiers that we can add to the main methods?
- What are all the changes allowed for the main method
- final synchronized strictfp
strictfp
- same floating-point results
- Ensures precision consistency
- Avoids hardware differences
- Applicable to : class, method
What are the methods exists in the Object class?
Enum?
- can Enum have methods?
  - Yes
How does JVM divide/allocate memory? or Memory types in JVM?
1. JVM memory = Heap + Stack + Method Area + PC + Native Stack
2. Heap
  - Stores objects & instance variables
3. Stack
  - Method calls
  - Local variables
4. Method Area
  - Class metadata
  - Static variables
  - Runtime constant pool
5. PC Register
  - Current instruction address
6. Native Method Stack
  - Native (C/C++) calls
I/O in Java? [ Files, Command line, Rest API, Serialization-Deserialization, etc ]
What is a Thread in Java?
- Instructions + Memory(Shared) + Control Flow
What is Multi-Threading?
Thread vs Process vs Program?
What is deadlock?
What is race condition?
What is a synchronized keyword?
What is thread-safety?
- Code works correctly, Even with multiple threads
How to overcome the deadlock situation?
- Avoid nested locks
- Use timeout
- Lock ordering
- Use tryLock()
Thread lifecycle?
- New → Runnable → Running → Blocked → Terminated
Sleep vs Wait methods?
- sleep() → Thread class → no lock release
- wait() → Object class → releases lock
What happens when we call the join method?
- Current thread waits
- Until another thread completes
Consumer and Producer problem example?
How many ways we can create Threads in Java? ***
- extending Thread
- implementing Runnable
- implementing Callable *
Why should we prefer implementing Runnable over the Extending Thread?
Callable vs Runnable? ***
What is a Future Object? ***
What is ExecutorServic ### Types of GC e? ***
What is ThreadPool?
What is BlockingQueue? ***
Did you use the reentrantlock? What is the use of it?
What are the new features in Java-8? *** - Lambda Expressions (Functional Programming) - Functional Interfaces ***
- Consumer *
- Supplier(Producer) *
- Predicate *
  - Stream API (Processing Collections Efficiently) ***
  - Default metods in interface
  - Method References (:: Operator)
  - Optional Class (Avoiding NullPointerException)
  - New Date & Time API (java.time Package)
  - Collectors in Stream API *
  - Base64 Encoding and Decoding
Rest parameters?
Optional return type?
What is a functional interface? - Interface with only one abstract method - Used for Lambda - Consumer, Supplier,and Predicate interfaces?
- Consumer<T> → takes input, no return
- Supplier<T> → no input, returns value
- Predicate<T> → returns boolean
What are the Lamda functions? - Short form of anonymous method - Used with functional interfaces
Can an interface have methods with the implementation?
Method reference? - Shortcut for lambda - Refers to existing method - Types
- Class::staticMethod
- obj::instanceMethod
- Class::new
What are streams in java? - Filter vs Map? - Stream vs ParallalStream? - Map vs FlatMap in streams?
Stream vs ParallelStream - Stream = single thread - ParallelStream = multi-threaded processing ✔️ - Stream
- Sequential processing
- Single thread
- Predictable order
- Good for small tasks - ParallelStream
- Parallel processing
- Multiple threads
- Faster for large data
- Uses ForkJoinPool
ForkJoinPool - Thread pool for parallel tasks - Uses work-stealing algorithm - Splits task (fork) - Merges result (join) - Used by:
- ParallelStream
- RecursiveTask / RecursiveAction
- ForkJoinPool = framework for parallel execution ✔️
How streams are faster than normal for loops - Streams are faster due to lazy execution + parallel processing ✔️ - Uses lazy evaluation - Supports parallel processing - Internal iteration optimization - Uses ForkJoinPool (for parallel streams) - Better CPU utilization
CompletableFeature? *
Sealed classes? *
Records? * - Special class to store immutable data - Auto generates: constructor, getters, equals, hashCode, toString - can Record extend another class?: No (already extends Record) - can Record implent interface?: Yes - can Record have methods?: Yes
how to create custom annotations ? *
How to implement the Singleton class?
Reflection?
What are Blocking collections? *
What are concurrent collections? *
what are CountDownLatch and CyclicBarrier in java.util.concurrent?
what is nio package?
- non-blocing io?
what is try with rerource? what are the benefits?
can we pass object in switch case?
- yes in java17 afterwards
  - in switch expression
  - also we can use Guarded Patterns
what are text blocks?
- multiline string after java13
in User class has name & age *** - using streams
- group users by name
- sort by age
- find 2nd youngest *
- find dublicate user
using streams *** - for a given string find no of occurance of each character *** - find dublicate chars *** - find unique chars *
Different Types of Deisgn Patterns?
What are major improvements in Hashmap after java7 - prevously
- linkedlist used
- Worst-case time complexity: O(n) when many keys collide
  - now
- initially linkedlist if capacity increased Red-Black Tree
- Worst-case time complexity: O(log n) when many keys collide
- Thresholds introduced
  - Untreeify threshold:6, Treeify threshold : 8, Min capacity for treeification: 64
  - Tree conversion (linkedlist to Red-Black Tree) happens only when:
    - Bucket size ≥ 8
    - HashMap capacity ≥ 64
major Garbage Collection (GC) improvements after Java 7 - After Java 7, Java 8 removed PermGen, introduced Metaspace, stabilized G1 GC - and later versions added ultra-low latency collectors like ZGC and Shenandoah. - In detail
- Java 7
  - PermGen (Fixed size) → OutOfMemoryError
  - Monolithic heap handling
- G1 GC ( java 8)
  - region based gc (Heap split into regions)
  - Predictable pause time goals
  - Low pause times ( Low latency GC )
  - Automatic heap compaction
  - Better for large heaps
  - Metaspace (Native memory) → Grows dynamically
  - Fewer OOM errors
  - Better class loading handling
  - Parallel GC
  - Better multi-core utilization
  - Smarter work stealing between GC threads
Ccan a static block throw exception
- yes, only unchecked exceptions ( RuntimeExceptions )
LinkedList in java is SingleLinkedList or DoublyLinkedList
Virtual Threads? - how they work? - Virtual Threads vs Platform threads?
If I create Strings using StringBuilder for the first time: - How many objects get created? - Does it create anything in the String Pool?

JDBC

What is a connection pool? *
How does Driver Manager connect to db?
Statement vs Prepared Statements ?

Servlets&Jsp

What is Servlet?
Lifecycle of Servlet?
- load class
- init() → called once
- service() → handles requests
- destroy()
Lifecycle of JSP?
- compilation
- load class
- init() → called once
- service() → handles requests
- destroy()

Spring MVC

What is spring?
What is AOP? *
- Separates cross-cutting concerns
- Logging, security, transactions
What is IOC? *
- Object creation handled by Spring
- Not by developer
What is dependency injection? *
What is a spring container?
- Manages bean lifecycle
- Creates & injects objects
- Examples: ApplicationContext
Singleton vs Prototype?
- Singleton → One object per container
- Prototype → New object every request
What is a session?
what are different scopes of a bean in spring or spring boot? ***
- singleton → default
- prototype
- request
- session
- application/applicationContext
- websocket

Spring Boot

What is a spring boot?
Spring vs Spring MVC vs Spring Boot? ***
What is maven?
What are the benefits of using spring boot over the spring MVC?
What are the different scopes in spring boot ( spring )? *** - Singleton, prototype, request, session, applicationContext, WebSocket
What are the different types of contexts?
1. BeanFactory: → Basic container
2. ApplicationContext: → Advanced container
3. ClassPathXmlApplicationContext: → Loads from classpath
4. FileSystemXmlApplicationContext: → Loads from file system
5. AnnotationConfigApplicationContext: → Java config (@Configuration)
6. WebApplicationContext: → Web apps
How many ways we can create beans in Spring boot? *
1. @Component: @Service, @Repository, @Controller
2. @Bean: Method level inside @Configuration
3. @Configuration + @Bean
4. XML configuration (legacy)
Controller vs RestContoller? *
What are interceptors? *
Component vs Controller vs Service vs Repository?
The life cycle of a bean? *
What @SpringBootApplication annotation does? ***
What @Configure, @EnableAutoConfiguration, @ComponentScan annotation do? *
- @Configure: Marks class as config class
- @EnableAutoConfiguration: Spring Boot auto config, Based on classpath & properties
- @ComponentScan: Scans packages, Finds @Component, @Service, @Repository
How many ways we can set the values in spring boot?
What @AutoWired annotation does?
What @Qualifies annotation does?
What is @Primary annotation does? *
How to read data(values) from application.properties?
- @Value
- @ConfigurationProperties
How to use environment-based properties files?
- spring.profiles.active=dev
- application-dev.properties, application-test.properties
I have application-dev.properties & application.properties & spring.profiles.active=dev
- then which proprty file is loaded
- A: Profile file has higher priority
  - Base file loads first(application.properties) → profile file overrides(application-dev)
What are profiles in spring boot?

@Profile

Used to enable/disable beans
Based on active environment

  @Profile("dev")
  @Component
  class DevBean { }

How to connect more than one DB using spring boot?
JPA vs CRUD repository?
What does @id, @transient annotation do?
How to execute custom DB queries in Spring boot?
- @Query
- @Modifier
- @Param
- Native Queries
- CriteriaBuilder
Hibernate Query Language Vs Native Query?
What @Transactional annotation does? ***
What is the connection pool?
getById vs findById?
EagerLoading vs LazyLoading? ***
How to handle exceptions or error handling? ***
- in controller
- in controller advice
How to handle global exceptions in spring boot? ***
How (best way ) to create threads in spring boot? ***
- Use @EnableAsync, @Async + ThreadPoolTaskExecutor
interceptors vs filters? *
- Filter
  - Part of Servlet
  - Runs before request enters controller
  - Works at container level
  - Use: logging, auth, CORS
  - Package: javax.servlet
- Interceptor
  - Part of Spring
  - Runs before/after controller
  - Works at framework level
  - Use: validation, auth, logging
  - Package: org.springframework
- Filter → runs earlier & Interceptor → runs after filter

Spring Boot Advance & Micro Services

Spring boot actuator
Caching *
- @EnableCaching ( @Cacheable, @CachePut, and @CacheEvict )
  - @Cacheable: the result of a method should be cached
CommandLineRunner
How to connect to multiple DBs? *
Internationalization (i18n)
Testing
- @SpringBootTest, @MockBean, and @DataJpaTest
JPA pagination
@Transactional *
- @Transactional(propagation = Propagation.NESTED)
@Configuration ***
- @ConditionalOnMissingBean
How to load beans conditionally? *
- @Conditional
- @Profile
@TransactionalEventListener
- @TransactionalEventListener = event handling tied to DB transaction state
- Phases
  - BEFORE_COMMIT
  - AFTER_COMMIT ✅ (most used)
  - AFTER_ROLLBACK
  - AFTER_COMPLETION
scheduled task
- @EnableScheduling
- @Scheduled
@ConfigurationProperties
- to bind application.properties to an object / class
file upload
@Import
@EnableAsync
- @Async
@DynamicPropertySource ( Testing )
database migrations
- Flyway
- Liquibase *
@Retryable
distributed caching *
- Redis *
- Hazelcast
distributed session management *
- Redis *
- Hazelcast
distributed locks *
- shedLock
@Lazy *
server-sent events (SSE)
@EventListener
How to Register a Custom Auto-Configuration?
How to Disable a Specific Auto-Configuration?
- If we want to disable a specific auto-configuration,
- we can indicate it using the exclude attribute of the @EnableAutoConfiguration annotation.
what are Spring Boot Starters
How to optimize API request
1. first DB level
  - primary keys
  - index
  - fetching required fields
  - avoding un-necessary joins
  - query pagination
2. using cache
3. Paginataion
4. Images as a seperate api
5. sending only required fields in response
DTO *
Bean vs Entity vs DTO

How to disable one specific package in spring boot

Exclude package from component scanning

 @SpringBootApplication(
     scanBasePackages = "com.myapp",
     excludeFilters = @ComponentScan.Filter(
         type = FilterType.REGEX,
         pattern = "com.myapp.unwanted.*"
     )
     )
     public class MyApp { }

Disable a specific auto-configuration(If the package is coming via auto-config)

  @SpringBootApplication(exclude = {
     DataSourceAutoConfiguration.class
     })

Disable via application.properties (Used when the package is conditionally enabled.)

   spring.autoconfigure.exclude=org.springframework.boot.autoconfigure.jdbc.DataSourceAutoConfiguration

Disable beans using @Profile

   @Profile("!prod")
     @Component
     public class TestOnlyBean { }

How to do our own auto configuration

Step 1: Create configuration class

   @Configuration
     @ConditionalOnClass(MyService.class)
     public class MyAutoConfiguration {

     @Bean
     @ConditionalOnMissingBean
     public MyService myService() {
         return new MyService();
     }
     }

Step:2 Register auto-config
- create a file (spring 3.+)
  - META-INF/spring/org.springframework.boot.autoconfigure.AutoConfiguration.imports
- add property
  - com.myapp.autoconfig.MyAutoConfiguration

Step 3: (Optional) Enable via properties

  @ConditionalOnProperty(
     name = "my.feature.enabled",
     havingValue = "true",
     matchIfMissing = false
     )

one liner:Auto-configuration uses conditions + classpath scanning + properties to configure beans automatically.

application.properties vs application.yaml

what are named queries?

Named Queries are static, pre-defined JPQL queries defined once and reused.
- Advantages
  - Validated at startup
  - Reusable
  - Cleaner code

eg:

   @Entity
   @NamedQuery(
      name = "User.findByEmail",
      query = "SELECT u FROM User u WHERE u.email = :email"
      )
  public class User { }

usage

      @Query(name = "User.findByEmail")
      User findByEmail(@Param("email") String email);

what are native queries?
- Native Queries use database-specific SQL, not JPQL.
  - When to use native queries?
    - Complex joins
    - Database-specific features
    - Performance-critical queries
    - Stored procedures
- eg:
```
 @Query(
  value = "SELECT * FROM users WHERE status = ?1",
  nativeQuery = true
  )
  List<User> findActiveUsers(String status);
```

Named vs Native Queries

Named Query	Native Query
Uses JPQL	Uses SQL
DB independent	DB dependent
Entity based	Table based

in Saga design pattern….one service executed 5 steps out of 7 & failed. How to handle this
How to pass dynamic values to CI pipelines
- secrets & config
- atrifact information

Spring Security

method-level security ( @PreAuthorize , @PostAuthorize, @Secured ) *
what is filterSecurityChain
How to secure mvc controller ? or APIs
- method level security
  - @PreAuthorize , @PostAuthorize, @Secured
- @EnableWebSecurity
  - SecurityFilterChain
    - authorizeHttpRequests & requestMatchers/matchPattern

Spring Boot Micro Services

did you work with any message queues
- RabbitMQ *
- Apachekafka *
How to communicate b/w the micro services *
- Synchronus comminication
  - REST
  - GraphQL
  - GRPC
- ASynchronus comminication
  - Event-driven architecture
    - Messaging Queues
      - RabbitMQ *
      - Apachekafka *
OpenTelemetry metrics, logs, and traces
How to see logs in Micro services ***
- ELK Stack (Elasticsearch, Logstash, Kibana)
- Promtail & Loki
Observaility in micro services ***
- logger
  - ELK Stack (Elasticsearch, Logstash, Kibana) *
  - Promtail & Loki *
- Metrics
  - Spring Boot Actuator with MicroMeter plugin & Prometheus
- Tracing
  - Spring Boot Actuator with zapkin plugin & Tempo
- Dashboard
  - Grafana

Observaility *

          Spring Boot                         ----> Centalized Service
   ==================================================================================
  Logging:  Logstash                          ----> Elasticsearch for storage & Kibana for View
              (or)
  Logging:  Logstash                          ----> Elasticsearch for storage & Loki for View

  Metrics:  Actuator with MicroMeter plugin   ----> Prometheus
  Tracing:  Actuator with zapkin plugin       ---->  Tempo

What are different types of Micro Service Architecture Design Patterns?
Application Performance Monitoring (APM) tool
- used to monitor, analyze, and optimize application performance in real time.
- AppDynamics

Java Interview Questions

Java Interview Questions

Core Java

`How GC works`

JDBC

Servlets&Jsp

Spring MVC

Spring Boot

Spring Boot Advance & Micro Services

Spring Security

Spring Boot Micro Services

Other Spring Boot Topics