Observability of the Java Virtual Machine

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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=...
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My Crappy Looking Solution to "Binary Tree Common Ancestor" Problem

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I was able to solve this problem and make all the tests pass:

https://www.hackerrank.com/challenges/binary-search-tree-lowest-common-ancestor/problem

But I'm not happy with the code, so later I need to refactor the code. Here it is:

static Node lca(Node root, int v1, int v2) {

    ArrayList result = new ArrayList<>();

    Node result2 =
            traverse(root, v1, v2, result);

    if (result.isEmpty())
        return result2;

    return result.get(0);
}


private static Node traverse(Node root, int v1, int v2, ArrayList result) {

    if (!result.isEmpty()) {
        return result.get(0);
    }

    if (root.left == null && root.right == null) {
        return root;
    }

    if (root.data == v1 || root.data == v2) {
        return root;
    }

    Node node1 = null, node2 = null;

    if (root.left != null)
        node1 = traverse(root.left, v1, v2, result);

    if (root.right != null)
        node2 = traverse(root.right, v1, v2, result);

    if (!result.isEmpty()) {
        return result.get(0);
    }

    if (node1 != null && node1.data == v1 &&
            node2 != null && node2.data == v2) {
        result.add(root);
        return root;
    }
    if (node1 != null && node1.data == v2 &&
            node2 != null && node2.data == v1) {
        result.add(root);
        return root;
    }


    if (node1 == null && node2 == null)
        return null;

    if (node1 != null && node1.data == v1) {
        return node1;
    }
    if (node1 != null && node1.data == v2) {
        return node1;
    }
    if (node2 != null && node2.data == v1) {
        return node2;
    }
    if (node2 != null && node2.data == v2) {
        return node2;
    }


    return null;
}




Thanks to this youtube channel for describing the algorithm:




https://www.youtube.com/watch?v=F-_1sbnPbWQ&t=301s


































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