Author: Editorial Team
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How Do You Debug and Fix a Memory Leak in a Production JVM?
1. Introduction Memory leaks in Java applications can cause severe performance degradation, frequent OutOfMemoryErrors, and even complete system crashes. While Java has garbage collection, leaks can still occur if references to unused objects are unintentionally held. 2. What Is a Memory Leak in Java? In Java, a memory leak occurs when an object is no…
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Comparing synchronized vs StampedLock vs VarHandle for Concurrency Control in Java
Overview Java provides multiple mechanisms to control access to shared resources in a concurrent environment: Feature Synchronized Block StampedLock VarHandle Type Intrinsic Lock Explicit Lock Low-Level Memory Access Read/Write Support No distinction Yes (Optimistic, Pessimistic) No lock abstraction Reentrancy Yes No Not applicable Fairness Not guaranteed Not guaranteed Not applicable Best Use Case Simplicity, legacy…
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How the Java Memory Model (JMM) Ensures Visibility and Ordering of Operations in Multi-Core Systems
1. Introduction Java applications often run on multi-core, multi-threaded systems, where multiple threads can read and write shared variables concurrently. While this enables powerful parallelism, it introduces serious challenges around memory visibility, instruction ordering, and data consistency. To address this, Java introduced the Java Memory Model (JMM) in Java 1.5 (JSR-133) as part of the…
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Scalability Challenges with ConcurrentHashMap under High Contention and How to Optimize It
1. Introduction Java’s ConcurrentHashMap is a thread-safe implementation of a hash-based map that allows concurrent reads and updates without requiring full synchronization. It was designed to scale better than Collections.synchronizedMap() or Hashtable in multi-threaded environments. However, when multiple threads frequently access or modify the map, especially on the same keys or buckets, performance bottlenecks can…
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Leftmost Column with at Least a One
Problem Statement You are given a binary matrix (only 0s and 1s) binaryMatrix where: You can access the matrix only through an API: Goal: Minimize the number of get() calls. Example Key Observations Approach: Top-Right Pointer Java Code Dry Run Example Input Matrix Return: 1
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Search in Rotated Sorted Array
1. Problem Statement You are given an integer array nums that was originally sorted in ascending order, but then rotated at some pivot. For example: Given the rotated array nums and an integer target, return the index of target if it is in nums. Otherwise, return -1. 1.1 Constraints: 1.2 Example 2. Intuition Even though…
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Minimum Path Sum
Problem Statement You are given an m x n grid filled with non-negative integers, representing the cost to travel through each cell. You can only move right or down at any point in time. Return the minimum sum of the path from the top-left corner (0, 0) to the bottom-right corner (m-1, n-1). Example Key…
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Number of Islands
Problem Description You’re given a 2D grid of characters ‘1’ (land) and ‘0’ (water). You need to find the number of islands in the grid. Rules: Example Input: Output: Explanation: Approach Overview The problem is fundamentally a graph traversal problem: We can solve this using: We’ll use DFS in this tutorial because it’s intuitive and…
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Valid Parenthesis String
Problem Statement: Given a string s containing only ‘(‘, ‘)’, and ‘*’, return true if the string is valid. A string is valid if: Examples: Example 1: Example 2: Example 3: Example 4: The challenge is that ‘*’ can be anything: This means we need to consider multiple possible interpretations. Greedy Two-Pointer Method (Optimized O(n)…
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Product of Array Except Self
Problem Statement: Given an integer array nums, return an array answer such that: Example: Input: Output: Explanation: Intuition and Approach (Without Division) We cannot use division, so we need to calculate the product of elements before and after each index, then multiply them. Idea: Let: But to save space, we reuse the result array and…