Why Java Programming Is Important for Businesses in 2026

// Java record (Java 16+): a concise, immutable data class
public record Invoice(String id, String customer, double amount) {
    public Invoice {
        if (amount < 0) {
            throw new IllegalArgumentException("amount cannot be negative");
        }
    }
}

# Check installed Java version
java -version
# List LTS releases you are likely to meet at work:
# Java 8, 11, 17, 21 (and newer LTS versions over time)
# New projects usually start on the latest LTS.

import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;

public class SalesReport {
    record Sale(String region, double amount) {}

    public static void main(String[] args) {
        List<Sale> sales = List.of(
            new Sale("North", 1200), new Sale("South", 800),
            new Sale("North", 500));
        Map<String, Double> byRegion = sales.stream()
            .collect(Collectors.groupingBy(Sale::region,
                     Collectors.summingDouble(Sale::amount)));
        System.out.println(byRegion);
    }
}

import java.sql.*;

String sql = "SELECT id, name FROM customers WHERE city = ?";
try (Connection con = DriverManager.getConnection(url, user, pass);
     PreparedStatement ps = con.prepareStatement(sql)) {
    ps.setString(1, "Noida");
    try (ResultSet rs = ps.executeQuery()) {
        while (rs.next()) {
            System.out.println(rs.getInt("id") + " " + rs.getString("name"));
        }
    }
}

import java.util.concurrent.Executors;

public class Demo {
    public static void main(String[] args) {
        try (var executor = Executors.newVirtualThreadPerTaskExecutor()) {
            for (int i = 0; i < 10_000; i++) {
                int id = i;
                executor.submit(() -> {
                    Thread.sleep(100);   // simulates waiting on I/O
                    return id;
                });
            }
        } // waits for all tasks to finish
        System.out.println("done");
    }
}

sealed interface Payment permits Card, Upi {}
record Card(String last4) implements Payment {}
record Upi(String vpa) implements Payment {}

static String describe(Payment p) {
    return switch (p) {
        case Card c -> "Card ending " + c.last4();
        case Upi u  -> "UPI " + u.vpa();
    };
}

package com.example.orders;

import org.springframework.web.bind.annotation.*;
import java.util.List;

@RestController
@RequestMapping("/api/orders")
public class OrderController {
    record Order(long id, String item, int qty) {}

    @GetMapping
    public List<Order> all() {
        return List.of(new Order(1, "Laptop", 1), new Order(2, "Mouse", 2));
    }
}

package com.example.orders;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class OrdersApplication {
    public static void main(String[] args) {
        SpringApplication.run(OrdersApplication.class, args);
    }
}
// Generate the project at start.spring.io with 'Spring Web',
// run ./mvnw spring-boot:run and open /api/orders

Phase 1: Core Java - OOP, collections, exceptions
Phase 2: Modern Java - records, streams, switch patterns
Phase 3: SQL + JDBC basics
Phase 4: Spring Boot - REST APIs, validation
Phase 5: Spring Data JPA + a real database
Phase 6: Testing with JUnit 5 + one deployed project