Java senior-level topics

TL;DR

In this blog post, I will go over some of the more advanced topics in Java that are commonly asked in coding interviews. These topics make or break a lot of candidates, so it is important to be familiar with them. These topics include design patterns, data structures, algorithms, multithreading, concurrency, and immutable types.

Senior-level problems

Multithreading:

• The synchronized keyword in Java is used to indicate that a method or block of code can only be executed by one thread at a time. This is useful for ensuring thread safety and preventing race conditions.
• The volatile keyword in Java is used to indicate that a variable may be modified by multiple threads concurrently. This ensures that all threads see a consistent value for the variable.
• The java.util.concurrent package contains a number of useful classes for working with threads and concurrency in Java. Some common classes in this package include Executor, Semaphore, and ConcurrentHashMap.
• The Thread.join() method allows one thread to wait for the completion of another thread. It can be called on a thread instance and will block the calling thread until the thread it is called on has completed.

Concurrency:

• The java.util.concurrent.atomic package contains classes that provide atomic operations for working with primitive types and object references. These classes are useful for implementing thread-safe algorithms without using locks. Some common classes in this package include AtomicInteger, AtomicLong, and AtomicReference.
• The java.util.concurrent.locks package contains classes that provide more advanced locking mechanisms than the synchronized keyword. These classes are useful for implementing complex synchronization schemes and for controlling access to shared resources. Some common classes in this package include ReentrantLock, ReadWriteLock, and Condition.
• The java.util.concurrent.Executor interface provides a way to run tasks concurrently using a thread pool. Some common implementations of this interface include ThreadPoolExecutor and ScheduledThreadPoolExecutor.
• Some common ways to safely share data between threads in Java include using thread-safe data structures from the java.util.concurrent package, using the synchronized keyword or java.util.concurrent.locks classes to control access to shared resources, and using the java util.concurrent.atomic classes to perform atomic operations on shared data.

Immutable types:

• An immutable type is a type whose value cannot be changed after it has been created. This is useful because it ensures that the value of an object will always remain the same, making it easier to reason about and more predictable.
• The java.lang.String class is an immutable class in Java. This means that once a String object has been created, its value cannot be changed.
• The java.util.Date class is a mutable class in Java. This means that the value of a Date object can be changed after it has been created.
• To create an immutable class in Java, you should make the class final so that it cannot be subclassed, and make all of its fields final and private so that they cannot be modified. You should also provide only getter methods for accessing the fields, and not provide any methods for modifying the fields.