Java code explainers

java

public final class BusinessDays {
 
    private BusinessDays() {
    }

Counting business days between two dates in Java

date arithmetic utility class streams

Intermediate 7 steps

java

import java.time.Duration;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.ScheduledFuture;

A safe recurring heartbeat scheduler in Java

concurrency scheduling thread-safety

Intermediate 6 steps

java

package com.example.monitoring;
 
import org.springframework.boot.actuate.health.Health;
import org.springframework.boot.actuate.health.HealthIndicator;

A custom replica health check in Spring

health-check actuator monitoring

Intermediate 7 steps

java

@Repository
public interface OrderRepository extends JpaRepository<Order, Long> {
 
    @QueryHints(@QueryHint(name = HINT_FETCH_SIZE, value = "1000"))

Streaming large result sets in Spring Data JPA

streaming jpa memory-management

Advanced 6 steps

java

import java.util.ArrayList;
import java.util.Comparator;
import java.util.HashSet;
import java.util.List;

Three ways to deduplicate a list by key in Java

streams deduplication collectors

Intermediate 6 steps

java

public class UnionFind {
    private final int[] parent;
    private final int[] rank;
    private int count;

How union-find with path compression works

disjoint-set path-compression union-by-rank

Intermediate 7 steps

java

import java.util.*;
 
public class TopologicalSort {

Topological sort with Kahn's algorithm

graphs topological-sort bfs

Intermediate 6 steps

java

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;

Java try-with-resources and AutoCloseable

try-with-resources autocloseable resource-management

Intermediate 6 steps

java

import java.util.Arrays;
 
public class SlidingWindow {
    // Returns the maximum sum of any contiguous subarray of length k.

The sliding window technique in Java

sliding-window arrays algorithms

Intermediate 8 steps

java

import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;

Breadth-first search on an adjacency-list graph

graph-traversal bfs adjacency-list

Intermediate 7 steps

java

public final class Quicksort {
 
    private Quicksort() {
    }

Quicksort with Lomuto partitioning in Java

recursion divide-and-conquer in-place

Intermediate 7 steps