Exploring Modern Java: Key Language Features from Java 9 to 22 in a single program

03411

Java has evolved significantly over the years, introducing powerful new features that enhance readability, performance, and developer productivity. In this article, we explore key language improvements from Java 9 to Java 22, including the Java Platform Module System, local variable type inference, switch expressions, text blocks, record classes, sealed types, and advanced pattern matching. Through a practical Java program, we demonstrate how these features work together to simplify coding and improve maintainability. Whether you’re a seasoned developer or just starting with modern Java, this guide will help you stay up to date with the latest advancements. 

<span>import</span> <span>java.util.*</span><span>;</span>
<span>// Java 16: Record Classes (JEP 395)</span>
<span>record</span> <span>Person</span><span>(</span><span>String</span> <span>name</span><span>,</span> <span>int</span> <span>age</span><span>)</span> <span>{}</span>
<span>// Java 17: Sealed Classes (JEP 409)</span>
<span>sealed</span> <span>interface</span> <span>Animal</span> <span>permits</span> <span>Dog</span><span>,</span> <span>Cat</span> <span>{}</span>
<span>record</span> <span>Dog</span><span>(</span><span>String</span> <span>name</span><span>)</span> <span>implements</span> <span>Animal</span> <span>{}</span>
<span>record</span> <span>Cat</span><span>(</span><span>String</span> <span>name</span><span>)</span> <span>implements</span> <span>Animal</span> <span>{}</span>
<span>public</span> <span>class</span> <span>JavaFeaturesDemo</span> <span>{</span>
    <span>public</span> <span>static</span> <span>void</span> <span>main</span><span>(</span><span>String</span><span>[]</span> <span>args</span><span>)</span> <span>{</span>
        <span>// Java 10: Local Variable Type Inference (JEP 286)</span>
        <span>var</span> <span>message</span> <span>=</span> <span>"Hello, Java!"</span><span>;</span>
        <span>System</span><span>.</span><span>out</span><span>.</span><span>println</span><span>(</span><span>message</span><span>);</span>
        <span>// Java 11: Local-Variable Syntax for Lambda Parameters (JEP 323)</span>
        <span>List</span><span><</span><span>String</span><span>></span> <span>names</span> <span>=</span> <span>List</span><span>.</span><span>of</span><span>(</span><span>"Alice"</span><span>,</span> <span>"Bob"</span><span>,</span> <span>"Charlie"</span><span>);</span>
        <span>names</span><span>.</span><span>forEach</span><span>((</span><span>var</span> <span>name</span><span>)</span> <span>-></span> <span>System</span><span>.</span><span>out</span><span>.</span><span>println</span><span>(</span><span>"Hello, "</span> <span>+</span> <span>name</span><span>));</span>
        <span>// Java 14: Switch Expressions and Statements (JEP 361)</span>
        <span>int</span> <span>day</span> <span>=</span> <span>3</span><span>;</span>
        <span>var</span> <span>dayType</span> <span>=</span> <span>switch</span> <span>(</span><span>day</span><span>)</span> <span>{</span>
            <span>case</span> <span>1</span><span>,</span> <span>2</span><span>,</span> <span>3</span><span>,</span> <span>4</span><span>,</span> <span>5</span> <span>-></span> <span>"Weekday"</span><span>;</span>
            <span>case</span> <span>6</span><span>,</span> <span>7</span> <span>-></span> <span>"Weekend"</span><span>;</span>
            <span>default</span> <span>-></span> <span>"Unknown"</span><span>;</span>
        <span>};</span>
        <span>System</span><span>.</span><span>out</span><span>.</span><span>println</span><span>(</span><span>"Day type: "</span> <span>+</span> <span>dayType</span><span>);</span>
        <span>// Java 15: Text Blocks (JEP 378)</span>
        <span>String</span> <span>json</span> <span>=</span> <span>""" { "name": "John", "age": 30 } """</span><span>;</span>
        <span>System</span><span>.</span><span>out</span><span>.</span><span>println</span><span>(</span><span>"JSON Data: "</span> <span>+</span> <span>json</span><span>);</span>
        <span>// Java 16: Pattern Matching with instanceof (JEP 394)</span>
        <span>Object</span> <span>obj</span> <span>=</span> <span>"Pattern Matching Example"</span><span>;</span>
        <span>if</span> <span>(</span><span>obj</span> <span>instanceof</span> <span>String</span> <span>str</span><span>)</span> <span>{</span>
            <span>System</span><span>.</span><span>out</span><span>.</span><span>println</span><span>(</span><span>"String length: "</span> <span>+</span> <span>str</span><span>.</span><span>length</span><span>());</span>
        <span>}</span>
        <span>// Java 21: Record Patterns (JEP 440) and Pattern Matching with switch (JEP 441)</span>
        <span>Person</span> <span>person</span> <span>=</span> <span>new</span> <span>Person</span><span>(</span><span>"John"</span><span>,</span> <span>25</span><span>);</span>
        <span>switch</span> <span>(</span><span>person</span><span>)</span> <span>{</span>
            <span>case</span> <span>Person</span><span>(</span><span>var</span> <span>name</span><span>,</span> <span>var</span> <span>age</span><span>)</span> <span>-></span> <span>System</span><span>.</span><span>out</span><span>.</span><span>println</span><span>(</span><span>"Person: "</span> <span>+</span> <span>name</span> <span>+</span> <span>", Age: "</span> <span>+</span> <span>age</span><span>);</span>
        <span>}</span>
        <span>// Java 22: Unnamed Variables and Patterns (JEP 456)</span>
        <span>Person</span> <span>unnamedPerson</span> <span>=</span> <span>new</span> <span>Person</span><span>(</span><span>"Jane"</span><span>,</span> <span>30</span><span>);</span>
        <span>if</span> <span>(</span><span>unnamedPerson</span> <span>instanceof</span> <span>Person</span><span>(</span><span>String</span> <span>_</span><span>,</span> <span>int</span> <span>age</span><span>))</span> <span>{</span>
            <span>System</span><span>.</span><span>out</span><span>.</span><span>println</span><span>(</span><span>"Age: "</span> <span>+</span> <span>age</span><span>);</span>
        <span>}</span>
    <span>}</span>
<span>}</span>
<span>import</span> <span>java.util.*</span><span>;</span>

<span>// Java 16: Record Classes (JEP 395)</span>
<span>record</span> <span>Person</span><span>(</span><span>String</span> <span>name</span><span>,</span> <span>int</span> <span>age</span><span>)</span> <span>{}</span>

<span>// Java 17: Sealed Classes (JEP 409)</span>
<span>sealed</span> <span>interface</span> <span>Animal</span> <span>permits</span> <span>Dog</span><span>,</span> <span>Cat</span> <span>{}</span>
<span>record</span> <span>Dog</span><span>(</span><span>String</span> <span>name</span><span>)</span> <span>implements</span> <span>Animal</span> <span>{}</span>
<span>record</span> <span>Cat</span><span>(</span><span>String</span> <span>name</span><span>)</span> <span>implements</span> <span>Animal</span> <span>{}</span>

<span>public</span> <span>class</span> <span>JavaFeaturesDemo</span> <span>{</span>
    <span>public</span> <span>static</span> <span>void</span> <span>main</span><span>(</span><span>String</span><span>[]</span> <span>args</span><span>)</span> <span>{</span>
        <span>// Java 10: Local Variable Type Inference (JEP 286)</span>
        <span>var</span> <span>message</span> <span>=</span> <span>"Hello, Java!"</span><span>;</span>
        <span>System</span><span>.</span><span>out</span><span>.</span><span>println</span><span>(</span><span>message</span><span>);</span>

        <span>// Java 11: Local-Variable Syntax for Lambda Parameters (JEP 323)</span>
        <span>List</span><span><</span><span>String</span><span>></span> <span>names</span> <span>=</span> <span>List</span><span>.</span><span>of</span><span>(</span><span>"Alice"</span><span>,</span> <span>"Bob"</span><span>,</span> <span>"Charlie"</span><span>);</span>
        <span>names</span><span>.</span><span>forEach</span><span>((</span><span>var</span> <span>name</span><span>)</span> <span>-></span> <span>System</span><span>.</span><span>out</span><span>.</span><span>println</span><span>(</span><span>"Hello, "</span> <span>+</span> <span>name</span><span>));</span>

        <span>// Java 14: Switch Expressions and Statements (JEP 361)</span>
        <span>int</span> <span>day</span> <span>=</span> <span>3</span><span>;</span>
        <span>var</span> <span>dayType</span> <span>=</span> <span>switch</span> <span>(</span><span>day</span><span>)</span> <span>{</span>
            <span>case</span> <span>1</span><span>,</span> <span>2</span><span>,</span> <span>3</span><span>,</span> <span>4</span><span>,</span> <span>5</span> <span>-></span> <span>"Weekday"</span><span>;</span>
            <span>case</span> <span>6</span><span>,</span> <span>7</span> <span>-></span> <span>"Weekend"</span><span>;</span>
            <span>default</span> <span>-></span> <span>"Unknown"</span><span>;</span>
        <span>};</span>
        <span>System</span><span>.</span><span>out</span><span>.</span><span>println</span><span>(</span><span>"Day type: "</span> <span>+</span> <span>dayType</span><span>);</span>

        <span>// Java 15: Text Blocks (JEP 378)</span>
        <span>String</span> <span>json</span> <span>=</span> <span>""" { "name": "John", "age": 30 } """</span><span>;</span>
        <span>System</span><span>.</span><span>out</span><span>.</span><span>println</span><span>(</span><span>"JSON Data: "</span> <span>+</span> <span>json</span><span>);</span>

        <span>// Java 16: Pattern Matching with instanceof (JEP 394)</span>
        <span>Object</span> <span>obj</span> <span>=</span> <span>"Pattern Matching Example"</span><span>;</span>
        <span>if</span> <span>(</span><span>obj</span> <span>instanceof</span> <span>String</span> <span>str</span><span>)</span> <span>{</span>
            <span>System</span><span>.</span><span>out</span><span>.</span><span>println</span><span>(</span><span>"String length: "</span> <span>+</span> <span>str</span><span>.</span><span>length</span><span>());</span>
        <span>}</span>

        <span>// Java 21: Record Patterns (JEP 440) and Pattern Matching with switch (JEP 441)</span>
        <span>Person</span> <span>person</span> <span>=</span> <span>new</span> <span>Person</span><span>(</span><span>"John"</span><span>,</span> <span>25</span><span>);</span>
        <span>switch</span> <span>(</span><span>person</span><span>)</span> <span>{</span>
            <span>case</span> <span>Person</span><span>(</span><span>var</span> <span>name</span><span>,</span> <span>var</span> <span>age</span><span>)</span> <span>-></span> <span>System</span><span>.</span><span>out</span><span>.</span><span>println</span><span>(</span><span>"Person: "</span> <span>+</span> <span>name</span> <span>+</span> <span>", Age: "</span> <span>+</span> <span>age</span><span>);</span>
        <span>}</span>

        <span>// Java 22: Unnamed Variables and Patterns (JEP 456)</span>
        <span>Person</span> <span>unnamedPerson</span> <span>=</span> <span>new</span> <span>Person</span><span>(</span><span>"Jane"</span><span>,</span> <span>30</span><span>);</span>
        <span>if</span> <span>(</span><span>unnamedPerson</span> <span>instanceof</span> <span>Person</span><span>(</span><span>String</span> <span>_</span><span>,</span> <span>int</span> <span>age</span><span>))</span> <span>{</span>
            <span>System</span><span>.</span><span>out</span><span>.</span><span>println</span><span>(</span><span>"Age: "</span> <span>+</span> <span>age</span><span>);</span>
        <span>}</span>
    <span>}</span>
<span>}</span>
import java.util.*;

// Java 16: Record Classes (JEP 395)
record Person(String name, int age) {}

// Java 17: Sealed Classes (JEP 409)
sealed interface Animal permits Dog, Cat {}
record Dog(String name) implements Animal {}
record Cat(String name) implements Animal {}

public class JavaFeaturesDemo {
    public static void main(String[] args) {
        // Java 10: Local Variable Type Inference (JEP 286)
        var message = "Hello, Java!";
        System.out.println(message);

        // Java 11: Local-Variable Syntax for Lambda Parameters (JEP 323)
        List<String> names = List.of("Alice", "Bob", "Charlie");
        names.forEach((var name) -> System.out.println("Hello, " + name));

        // Java 14: Switch Expressions and Statements (JEP 361)
        int day = 3;
        var dayType = switch (day) {
            case 1, 2, 3, 4, 5 -> "Weekday";
            case 6, 7 -> "Weekend";
            default -> "Unknown";
        };
        System.out.println("Day type: " + dayType);

        // Java 15: Text Blocks (JEP 378)
        String json = """ { "name": "John", "age": 30 } """;
        System.out.println("JSON Data: " + json);

        // Java 16: Pattern Matching with instanceof (JEP 394)
        Object obj = "Pattern Matching Example";
        if (obj instanceof String str) {
            System.out.println("String length: " + str.length());
        }

        // Java 21: Record Patterns (JEP 440) and Pattern Matching with switch (JEP 441)
        Person person = new Person("John", 25);
        switch (person) {
            case Person(var name, var age) -> System.out.println("Person: " + name + ", Age: " + age);
        }

        // Java 22: Unnamed Variables and Patterns (JEP 456)
        Person unnamedPerson = new Person("Jane", 30);
        if (unnamedPerson instanceof Person(String _, int age)) {
            System.out.println("Age: " + age);
        }
    }
}

Enter fullscreen mode Exit fullscreen mode

One way to improve your understanding of the latest Java changes is by taking Oracle Java Certifications.

原文链接：Exploring Modern Java: Key Language Features from Java 9 to 22 in a single program

© 版权声明
文章版权声明 1、本网站名称：拾光赋
2、本站永久网址：https://www.blogs.ink
3、本网站的文章部分内容可能来源于网络，仅供大家学习与参考，如有侵权，请联系站长QQ：805375623进行删除处理。
4、本站一切资源不代表本站立场，并不代表本站赞同其观点和对其真实性负责。
5、本站一律禁止以任何方式发布或转载任何违法的相关信息，访客发现请向站长举报
6、本站资源大多存储在云盘，如发现链接失效，请联系我们我们会第一时间更新。

THE END
Java（EN）
# java# programming# softwaredevelopment# software
喜欢就支持一下吧
点赞11 分享
Life must be lived with love, happiness, and dreams.
人生一定要有爱，有快乐，有梦想
kity的头像-拾光赋
相关推荐
评论 抢沙发

请登录后发表评论

    暂无评论内容

kity的头像-拾光赋
今日剩余 87.5%
本周剩余 26.8%
本月剩余 54.4%
本年剩余 80.0%
最近评论
Vito的头像-拾光赋

Vito5个月前2

你就是我心中的那首忐忑，总是让我惊心动魄
Jason.Meng的头像-拾光赋钻石会员

Jason.Meng徽章-人气大使-拾光赋5个月前2

总是会在人生的不同阶段反复爱上大佬的文章~
每日一言
Life must be lived with love, happiness, and dreams.
人生一定要有爱，有快乐，有梦想