Posts

Showing posts with the label algorithms

Observability of the Java Virtual Machine

Image
The JVM is one of the most observable runtimes. It provides us lots of tools for troubleshooting a JVM application in production. 1. Thread observability Threads are how the JVM actually does work. When something is wrong in production, the symptom is almost always a thread: stopped, blocked, leaking etc. Thread dumps work on any JVM with no  instrumentation, no agents, no restarts. <Example project link with /threaddump endpoint>         // (1) Deadlock — two threads grab the same pair of locks in opposite order.         new Thread(() -> grab(LOCK_A, LOCK_B), "deadlock-A-then-B").start();         new Thread(() -> grab(LOCK_B, LOCK_A), "deadlock-B-then-A").start(); http://localhost:8080/actuator/threaddump To list the JVMS, we can use the command below. PS C:\observe-jvm> jps -lv 25296 jdk.jcmd/sun.tools.jps.Jps -Dapplication.home=C:\Program Files\Microsoft\jdk-21.0.3.9-hotspot -Xms8m -Djdk.module.main=...

Dynamic Connectivity Problem and the Union-Find Algorithm

Lets say we need to connect some objects and query if some objects are connected or not. Below is an example test: @Test     public void testConnectivity() {         MyConnectionDb connectDb = new MyConnectionDb();         connectDb.connect(4, 3);         connectDb.connect(3, 8);         connectDb.connect(6, 5);         connectDb.connect(9, 4);         connectDb.connect(2, 1);         assertTrue(connectDb.isConnected(8, 9));         assertFalse(connectDb.isConnected(5, 4));         connectDb.connect(5, 0);         connectDb.connect(7, 2);         connectDb.connect(6, 1);         connectDb.connect(7, 3);         assertTrue(connectDb.isConnected(5, 3));     } So whe...

Popular posts from this blog

The WeakReference class, monitoring memory leak and garbage collection in a Java application

Simplescalar Simulator - Part 2: sim-outorder.c

Kotlin Language Features Related to Null Handling