MACJAVA8開發指南

隨著Java語言的不斷發展，越來越多的程序員選擇在MacOS環境中進行開發。這裡我們就要介紹一下如何在MacOS下使用Java8進行開發，並通過代碼實例來展示其各種功能。

一、環境搭建

1、MacOS系統環境

$ sw_vers
ProductName:	Mac OS X
ProductVersion:	10.15.4
BuildVersion:	19E266

2、JDK環境

$ java -version
java version "1.8.0_281"
Java(TM) SE Runtime Environment (build 1.8.0_281-b09)
Java HotSpot(TM) 64-Bit Server VM (build 25.281-b09, mixed mode)

3、Maven環境

$ mvn -v
Apache Maven 3.6.3
Maven home: /usr/local/Cellar/maven/3.6.3/libexec
Java version: 1.8.0_281, vendor: Oracle Corporation, runtime: /Library/Java/JavaVirtualMachines/jdk1.8.0_281.jdk/Contents/Home/jre
Default locale: en_US, platform encoding: UTF-8
OS name: "mac os x", version: "10.15.4", arch: "x86_64", family: "mac"

二、基本語法

1、Hello World實例代碼

public class HelloWorld {
    public static void main(String[] args) {
        // Prints "Hello, World" to the terminal window.
        System.out.println("Hello, World");
    }
}

2、變數和數據類型

public class VarTest {
    public static void main(String[] args) {
        // 聲明變數
        int a = 1;
        float b = 1.2f;
        double c = 3.1415926;
        boolean d = true;
        char e = 'a';
        String f = "Hello, World";
        System.out.println(a);
        System.out.println(b);
        System.out.println(c);
        System.out.println(d);
        System.out.println(e);
        System.out.println(f);
    }
}

3、循環和分支

public class LoopTest {
    public static void main(String[] args) {
        // if語句
        int a = 10;
        if (a < 20) {
            System.out.println("小於20");
        }
        // for循環
        for (int i = 0; i < 10; i++) {
            System.out.println(i);
        }
        // while循環
        int j = 0;
        while (j < 10) {
            System.out.println(j);
            j++;
        }
    }
}

三、常用類和方法

1、String類

public class StringTest {
    public static void main(String[] args) {
        String str1 = "Hello";
        String str2 = "World";
        String str3 = str1 + ", " + str2 + "!";
        System.out.println(str3);
        System.out.println(str3.toUpperCase());
        System.out.println(str3.toLowerCase());
        System.out.println(str3.substring(1,5));
        System.out.println(str3.indexOf("World"));
    }
}

2、List和Map集合

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class ListMapTest {
    public static void main(String[] args) {
        // List集合
        List list = new ArrayList();
        list.add("apple");
        list.add("banana");
        list.add("orange");
        for (String fruit : list) {
            System.out.println(fruit);
        }
        // Map集合
        Map map = new HashMap();
        map.put("name", "張三");
        map.put("age", 20);
        map.put("address", "北京市海淀區");
        for (String key : map.keySet()) {
            System.out.println(key + " -> " + map.get(key));
        }
    }
}

四、Web開發

1、Spring Boot實現RESTful API介面

@RestController
public class HelloController {
 
    @RequestMapping("/")
    public String index() {
        return "Hello, World!";
    }
 
    @RequestMapping("/hello")
    public String hello(@RequestParam(value = "name", required = false, defaultValue = "World") String name) {
        return "Hello, " + name + "!";
    }
 
    @RequestMapping("/user/{id}")
    public String user(@PathVariable int id) {
        return "User ID: " + id;
    }
}

2、Thymeleaf模板引擎實現頁面渲染

@Controller
public class UserController {

    @GetMapping("/users")
    public String userList(Model model) {
        List users = new ArrayList();
        users.add(new User(1, "張三", 20));
        users.add(new User(2, "李四", 25));
        users.add(new User(3, "王五", 30));
        model.addAttribute("users", users);
        return "users";
    }
}

五、總結

本文介紹了如何在MacOS環境中使用Java8進行開發，包括環境搭建、基本語法、常用類和方法以及Web開發。希望讀者能夠通過本文的介紹和實例，更好地了解Java8在MacOS上的應用。