Why Companies Still Stick with JDK 8 Even Though JDK 25 Is Released

Introduction

Many developers wonder why, even after JDK 25 has been released, a large number of companies still run their applications on JDK 8.

New projects often start with JDK 8, and legacy projects stubbornly remain on it.

Although newer versions bring attractive features and performance improvements, enterprises are reluctant to upgrade.

1. Compatibility Issues: New Bottle, Old Wine

1.1 API Changes and Removals

Each major JDK release removes or deprecates some internal APIs, causing existing code to fail. For example, JDK 8 code that uses sun.misc.BASE64Encoder for Base64 encoding compiles and runs, but the same code throws errors on JDK 9+ because the class has been removed.

import sun.misc.BASE64Encoder;
public class OldBase64Example {
    public String encode(String data) {
        BASE64Encoder encoder = new BASE64Encoder();
        return encoder.encode(data.getBytes());
    }
    public static void main(String[] args) {
        OldBase64Example example = new OldBase64Example();
        String result = example.encode("Hello, World!");
        System.out.println(result);
    }
}

The correct approach on newer JDKs is to use java.util.Base64:

import java.util.Base64;
public class NewBase64Example {
    public String encode(String data) {
        Base64.Encoder encoder = Base64.getEncoder();
        return encoder.encodeToString(data.getBytes());
    }
    public static void main(String[] args) {
        NewBase64Example example = new NewBase64Example();
        String result = example.encode("Hello, World!");
        System.out.println(result);
    }
}

Code logic analysis :

Old code directly uses JDK internal APIs that may change across versions.

New code uses standard APIs, ensuring cross‑version compatibility.

Even a simple change can affect hundreds or thousands of files in large projects.

1.2 Impact of the Module System

JDK 9 introduced the Java Platform Module System (JPMS), creating another compatibility hotspot. Developers may encounter class‑not‑found errors caused by module path issues.

// Common code in JDK 8
public class ReflectionExample {
    public void accessInternal() throws Exception {
        Class<?> clazz = Class.forName("sun.misc.Unsafe");
        Field field = clazz.getDeclaredField("theUnsafe");
        field.setAccessible(true);
        Object unsafe = field.get(null);
        // use unsafe ...
    }
}

In a modular project the module must explicitly declare its dependencies:

module com.example.myapp {
    requires java.base;
    requires jdk.unsupported; // explicit declaration
    exports com.example.mypackage;
}

Pros and cons comparison :

JDK 8: stable API, excellent compatibility, lower maintenance cost.

Newer JDKs: API changes frequently, higher maintenance effort.

Usage scenarios :

High‑stability production systems prefer JDK 8.

New projects with strong technical teams may adopt newer JDKs.

Frameworks heavily using reflection or internal APIs require careful upgrade planning.

2. Stability and Maturity: The Old Horse Knows the Road

2.1 Proven Runtime

The HotSpot VM in JDK 8 has been battle‑tested for nearly a decade, with most edge cases already discovered and fixed.

Newer runtimes such as GraalVM offer better raw performance but still need time to prove stability in production.

public class MemoryLeakExample {
    private static final int OBJECT_COUNT = 1000000;
    private static List<byte[]> list = new ArrayList<>();
    public void createMemoryLeak() {
        Random random = new Random();
        for (int i = 0; i < OBJECT_COUNT; i++) {
            int size = random.nextInt(1024) + 64;
            list.add(new byte[size]);
            if (random.nextDouble() < 0.3 && !list.isEmpty()) {
                list.remove(random.nextInt(list.size()));
            }
        }
    }
    public static void main(String[] args) throws InterruptedException {
        MemoryLeakExample example = new MemoryLeakExample();
        while (true) {
            example.createMemoryLeak();
            Thread.sleep(1000);
            System.out.println("Created " + list.size() + " objects");
        }
    }
}

JDK 8 memory management is well understood and optimized.

New GC algorithms (ZGC, Shenandoah) have better theoretical performance but may exhibit unexpected behavior in specific scenarios.

Enterprise applications cannot afford production crashes.

2.2 Ecosystem Maturity

JDK 8 enjoys the most complete ecosystem; mainstream frameworks and tools have deep optimizations for it. A typical Spring Boot configuration works flawlessly on JDK 8.

# application.yml
spring:
  datasource:
    url: jdbc:mysql://localhost:3306/test
    username: root
    password: password
  jpa:
    hibernate:
      ddl-auto: update
    show-sql: true

@Configuration
@EnableJpaRepositories
public class JpaConfig {
    @Bean
    @ConfigurationProperties("spring.datasource")
    public DataSource dataSource() {
        return DataSourceBuilder.create().build();
    }
}

Upgrading to newer JDKs may require module declarations or adjustments to library versions.

Stability comparison :

Financial, telecom, and other high‑stability industries usually stay on JDK 8.

Internet‑focused innovative businesses can experiment with newer versions.

Legacy systems without clear migration needs should avoid unnecessary upgrades.

3. Learning Cost and Team Adaptation: Rome Was Not Built in a Day

3.1 Learning Curve of New Features

JDK 9: Module system

JDK 10: Local variable type inference

JDK 11: HTTP Client API

JDK 14: Records, Pattern Matching

JDK 17: Sealed Classes

JDK 21: Virtual Threads

Example of a user‑information class evolving across versions:

// JDK 8 style
public class User {
    private final String name;
    private final int age;
    private final String email;
    public User(String name, int age, String email) {
        this.name = name;
        this.age = age;
        this.email = email;
    }
    // getters, equals, hashCode, toString ...
}

// JDK 14+ using Record
public record User(String name, int age, String email) {}

public class RecordExample {
    public void processUser() {
        User user = new User("Zhang San", 25, "[email protected]");
        System.out.println(user.name()); // generated getter
        System.out.println(user); // generated toString
    }
}

Although the new syntax is more concise, the team needs time to learn and adopt it.

3.2 Inertia of Team Skill Stack

Veteran developers are highly efficient with JDK 8.

New features require training and practice, temporarily affecting project progress.

Inconsistent code styles increase maintenance cost.

Usage scenarios :

Teams with strong learning culture can adopt newer versions quickly.

Traditional enterprises with low staff turnover prefer stability.

Newly formed teams may directly choose a newer JDK.

4. Third‑Party Dependency Support: Pull One Thread, Move the Whole Net

4.1 Framework and Library Compatibility

Spring Boot support matrix (simplified):

Spring Boot 2.7: supports JDK 8, 11, 17; not JDK 21.

Spring Boot 3.0: drops JDK 8 support, supports JDK 11, 17, 21.

MyBatis 3.5, Hibernate 5.6: support JDK 8‑21.

Upgrading may require adjusting module declarations, e.g. for Spring Boot 3.0 on JDK 17+:

// Spring Boot 2.x + JDK 8 typical entry
@SpringBootApplication
public class Application {
    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }
}

// If moving to JDK 17+, module info may be needed
module com.example.app {
    requires spring.boot;
    requires spring.boot.autoconfigure;
    requires spring.context;
    opens com.example to spring.core;
}

4.2 Cost of Dependency Conflicts

Upgrading JDK often forces library upgrades, which can introduce version conflicts.

// Example of a potential conflict
// library-a depends on guava:20.0
// library-b depends on guava:30.0
// After JDK upgrade both libraries may need newer versions that are incompatible.

New projects can freely choose newer tech stacks.

Legacy projects must evaluate compatibility of every dependency.

Micro‑service architectures allow incremental service‑by‑service upgrades.

5. Performance and Resource Considerations: Fast and Steady

5.1 Evolution of Garbage Collectors

From Parallel GC in JDK 8 to ZGC and Shenandoah in later releases, GC behavior changes significantly.

public class GCPressureTest {
    private static final int OBJECT_COUNT = 1000000;
    private static List<byte[]> objectPool = new ArrayList<>();
    public static void createGCPressure() {
        Random random = new Random();
        for (int i = 0; i < OBJECT_COUNT; i++) {
            int size = random.nextInt(1024) + 64;
            objectPool.add(new byte[size]);
            if (random.nextDouble() < 0.3 && !objectPool.isEmpty()) {
                objectPool.remove(random.nextInt(objectPool.size()));
            }
        }
    }
    public static void main(String[] args) throws InterruptedException {
        while (true) {
            createGCPressure();
            Thread.sleep(1000);
            System.out.println("Created " + objectPool.size() + " objects");
        }
    }
}

GC comparison (simplified):

Parallel GC (JDK 8+): longer pause, high throughput, low memory overhead.

G1 GC (JDK 9+): moderate pause and throughput, moderate overhead.

ZGC (JDK 15+): sub‑millisecond pauses, moderate throughput, high memory overhead.

Shenandoah (JDK 12+): short pauses, moderate throughput, high overhead.

5.2 Virtual Threads: Temptation and Challenges

Traditional thread‑pool example:

public class TraditionalThreadExample {
    private final ExecutorService executor = Executors.newFixedThreadPool(100);
    public void processRequests(List<Request> requests) {
        List<CompletableFuture<Result>> futures = requests.stream()
            .map(r -> CompletableFuture.supplyAsync(() -> processRequest(r), executor))
            .collect(Collectors.toList());
        CompletableFuture.allOf(futures.toArray(new CompletableFuture[0])).join();
    }
    private Result processRequest(Request request) {
        try { Thread.sleep(100); } catch (InterruptedException e) { /* handle */ }
        return new Result();
    }
}

Virtual‑thread version:

public class VirtualThreadExample {
    public void processRequests(List<Request> requests) {
        try (var executor = Executors.newVirtualThreadPerTaskExecutor()) {
            List<CompletableFuture<Result>> futures = requests.stream()
                .map(r -> CompletableFuture.supplyAsync(() -> processRequest(r), executor))
                .collect(Collectors.toList());
            CompletableFuture.allOf(futures.toArray(new CompletableFuture[0])).join();
        }
    }
    private Result processRequest(Request request) {
        try { Thread.sleep(100); } catch (InterruptedException e) { /* handle */ }
        return new Result();
    }
}

Usage scenarios :

IO‑intensive applications benefit greatly from virtual threads on a recent JDK.

CPU‑bound workloads may be fine with JDK 8.

Memory‑sensitive scenarios require careful GC testing.

6. Commercial Support and Cost Considerations: No Free Lunch

6.1 License and Support Cost

JDK 8 (LTS) receives support until 2030, giving enterprises ample migration time.

Non‑LTS releases have only six‑month support windows, leading to higher upgrade frequency and cost.

6.2 ROI Analysis of Upgrade

public class UpgradeROIAnalysis {
    // Direct costs
    private double hardwareCost;   // possible hardware upgrade
    private double softwareCost;   // license fees
    private double manpowerCost;   // labor
    private double trainingCost;    // training
    private double testingCost;    // testing
    // Indirect costs
    private double riskCost;       // risk
    private double downtimeCost;   // downtime
    // Expected gains
    private double performanceGain;
    private double maintenanceGain;
    private double securityGain;
    private double featureGain;
    public boolean shouldUpgrade() {
        double totalCost = hardwareCost + softwareCost + manpowerCost + trainingCost + testingCost + riskCost + downtimeCost;
        double totalGain = performanceGain + maintenanceGain + securityGain + featureGain;
        return totalGain > totalCost * 1.5; // require >1.5× ROI
    }
}

Usage scenarios :

Start‑ups can be aggressive, adopting newer versions for competitive advantage.

Traditional enterprises tend to wait for technology maturity.

Financial or government sectors often stay on JDK 8 until LTS support ends.

7. Toolchain and Infrastructure: Equip the Tools First

7.1 IDE and Build Tools

IntelliJ IDEA, Eclipse, Maven, Gradle all support JDK 8, 17, 21.

7.2 Monitoring and Diagnostic Tools

JDK 8 monitoring typically uses JMX:

public class JmxMonitoringExample {
    private final MBeanServer mbs = ManagementFactory.getPlatformMBeanServer();
    public void registerCustomMetric() throws Exception {
        ObjectName name = new ObjectName("com.example:type=CustomMetric");
        CustomMetric mbean = new CustomMetric();
        mbs.registerMBean(mbean, name);
    }
}

Newer JDKs offer Java Flight Recorder (JFR):

public class JfrMonitoringExample {
    @Label("Custom Event")
    @Description("Custom business event")
    static class CustomEvent extends Event {
        @Label("Event Data")
        private String data;
    }
    public void recordBusinessEvent(String data) {
        CustomEvent event = new CustomEvent();
        event.data = data;
        event.commit();
    }
}

Usage scenarios :

Mature projects prioritize a stable toolchain.

New projects can experiment with the latest tooling.

Hybrid environments need to ensure compatibility across the stack.

Conclusion

Risk control : Production stability outweighs novelty; JDK 8’s reliability is time‑tested.

Cost consideration : Upgrade costs (hardware, licenses, training, testing, risk) often exceed expected benefits.

Compatibility assurance : Existing code and third‑party libraries must remain functional.

Team efficiency : Familiar toolchains and skill sets keep development velocity high.

Business strategy : LTS versions align with long‑term enterprise planning.

Reasonable strategy:

New projects should consider LTS releases such as JDK 17 or JDK 21.

Legacy projects should avoid upgrades without clear business need.

Large systems can migrate incrementally, module by module.

Any upgrade must be validated with thorough testing.

Choosing the best technology means selecting the one that fits the business, not necessarily the newest.