Java全栈开发概述
全栈开发者需要掌握前端和后端技术，具备开发完整Web应用的能力。在Java领域，全栈开发者通常要精通Java语言，熟悉Java Web开发框架，了解前端技术（如HTML、CSS和JavaScript），具备数据库操作能力，并能进行系统设计和项目管理。在本书中，我们将从基础语法、面向对象编程到Java Web开发，逐步引导你成为全栈开发者。
Java基础
变量与数据类型
理解变量和数据类型是编程的基石。在Java中，变量用于存储数据，而数据类型定义了变量可以存储的特定类型的数据。
public class Variables {
public static void main(String[] args) {
int age = 25; // 整型变量
double weight = 68.5; // 浮点型变量
String name = "John Doe"; // 字符串变量
boolean isTall = true; // 布尔型变量
System.out.println("My name is " + name + ". I am " + age + " years old.");
System.out.println("My weight is " + weight + " kg.");
System.out.println("Am I tall? " + isTall);
}
}
运算符与流程控制
掌握基本的算术、比较、逻辑和条件运算，以及循环和选择结构，是编程中的必备技能。
public class Operators {
public static void main(String[] args) {
int x = 10;
int y = 5;
int sum = x + y;
int product = x * y;
int difference = x - y;
int quotient = x / y;
int remainder = x % y;
System.out.println("Sum: " + sum);
System.out.println("Product: " + product);
System.out.println("Difference: " + difference);
System.out.println("Quotient: " + quotient);
System.out.println("Remainder: " + remainder);
boolean greater = (x > y);
boolean lessOrEqual = (x <= y);
boolean equal = (x == y);
System.out.println("Is x greater than y? " + greater);
System.out.println("Is x less than or equal to y? " + lessOrEqual);
System.out.println("Are x and y equal? " + equal);
int i = 1;
while (i <= 5) {
System.out.println("Count: " + i);
i++;
}
boolean condition = true;
if (condition) {
System.out.println("Condition is true");
} else {
System.out.println("Condition is false");
}
}
}
面向对象编程
面向对象编程（OOP）让代码更加模块化和易于维护。Java是OOP的典范语言。
类与对象
类定义了对象的属性和方法，对象是类的实例。
public class Person {
private String name;
private int age;
public Person(String name, int age) {
this.name = name;
this.age = age;
}
public void introduce() {
System.out.println("Hello, my name is " + name + " and I am " + age + " years old.");
}
}
public class Main {
public static void main(String[] args) {
Person john = new Person("John", 30);
john.introduce();
}
}
封装、继承与多态
封装隐藏了对象的实现细节，继承允许创建新的类，而多态允许不同子类对象通过共同接口进行操作。
public class Employee extends Person {
private double salary;
public Employee(String name, int age, double salary) {
super(name, age);
this.salary = salary;
}
public void introduce() {
super.introduce();
System.out.println("My salary is " + salary);
}
public static void main(String[] args) {
Employee john = new Employee("John", 30, 50000);
john.introduce();
}
}
Java Web开发
Servlet与JSP
Servlet和JSP是Java Web开发的核心组件，用于处理HTTP请求和响应。
public class HelloWorldServlet extends HttpServlet {
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
response.getWriter().println("Hello, World!");
}
}
<!-- Example JSP page -->
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Hello World from JSP</title>
</head>
<body>
<h1>Hello, World!</h1>
</body>
</html>
JDBC与数据库操作
JDBC（Java Database Connectivity）用于连接和操作数据库。
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.Statement;
public class DatabaseConnection {
public static void main(String[] args) {
Connection conn = null;
try {
Class.forName("com.mysql.jdbc.Driver");
conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/yourDatabase", "username", "password");
Statement stmt = conn.createStatement();
String sql = "SELECT * FROM yourTable";
ResultSet rs = stmt.executeQuery(sql);
while (rs.next()) {
System.out.println("Column1: " + rs.getString("column1") + ", Column2: " + rs.getString("column2"));
}
} catch (Exception e) {
e.printStackTrace();
} finally {
try {
if (conn != null) {
conn.close();
}
} catch (Exception e) {
e.printStackTrace();
}
}
}
}
前端开发基础
HTML、CSS和JavaScript是构建Web应用的基础。
<!DOCTYPE html>
<html>
<head>
<title>Simple HTML Page</title>
<style>
body {
font-family: Arial, sans-serif;
margin: 20px;
}
h1 {
color: #333;
}
p {
color: #666;
}
</style>
</head>
<body>
<h1>Welcome to My Web Page</h1>
<p>This is a simple HTML page with some CSS styling.</p>
<script>
document.write("JavaScript content goes here");
</script>
</body>
</html>
实战项目
在本书的最后部分，我们将结合以上所有技术，开发一个完整的Web应用项目。通过项目实践，你将能把所学的知识应用到实际场景中，实现从理论到实践的飞跃。
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