JavaSE项目实战：从零开始构建实用应用

本文从JavaSE基础回顾、面向对象编程、集合框架、Swing组件与布局、IO流与NIO技术以及项目实战案例等多个角度，深入讲解JavaSE项目实战技术，旨在帮助开发者从零开始构建实用应用，通过具体代码示例，全面掌握JavaSE核心功能与实战技巧。

Java开发环境搭建

在开始之前，确保你的计算机上已经安装了Java开发环境（JDK）。可以访问Oracle官方网站下载最新版本的JDK，安装过程中确保勾选“Add to path”选项以便在任何位置直接使用Java命令。

Java基本语法与数据类型详解

变量与类型

public class VariableExample {
    public static void main(String[] args) {
        int age = 25;
        double height = 175.5;
        boolean isStudent = true;

        String name = "John Doe"; // 字符串类型与变量声明
        System.out.println("My age is " + age);
        System.out.println("My height is " + height);
        System.out.println("Am I a student? " + isStudent);
        System.out.println("My name is " + name);
    }
}

控制流程：循环与分支结构

public class ControlFlowExample {
    public static void main(String[] args) {
        for (int i = 1; i <= 5; i++) {
            System.out.println("Counting: " + i);
        }

        int score = 85;
        if (score >= 90) {
            System.out.println("Great job! You got an A.");
        } else if (score >= 70) {
            System.out.println("Good job! You got a B.");
        } else {
            System.out.println("Keep trying! You got a C.");
        }
    }
}

类与对象概念

public class Person {
    private String name;
    private int age;

    public Person(String name, int age) {
        this.name = name;
        this.age = age;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public void displayPerson() {
        System.out.println("Name: " + name + ", Age: " + age);
    }

    public static void main(String[] args) {
        Person person = new Person("John", 30);
        person.displayPerson();
    }
}

封装、继承与多态

封装

public class BankAccount {
    private double balance;

    public BankAccount(double initialBalance) {
        balance = initialBalance;
    }

    public double getBalance() {
        return balance;
    }

    public void deposit(double amount) {
        if (amount > 0) {
            balance += amount;
        }
    }

    public void withdraw(double amount) {
        if (amount > 0 && balance >= amount) {
            balance -= amount;
        }
    }
}

继承与多态

public class SavingAccount extends BankAccount {
    private double interestRate;

    public SavingAccount(double initialBalance, double interestRate) {
        super(initialBalance);
        this.interestRate = interestRate;
    }

    public void applyInterest() {
        double interest = balance * interestRate / 100;
        System.out.println("Interest: " + interest);
        balance += interest;
    }
}

public class Main {
    public static void main(String[] args) {
        BankAccount bankAccount = new BankAccount(1000);
        bankAccount.deposit(500);
        bankAccount.withdraw(200);
        System.out.println("Final balance: " + bankAccount.getBalance());

        SavingAccount savingAccount = new SavingAccount(1000, 5);
        savingAccount.deposit(500);
        savingAccount.withdraw(200);
        savingAccount.applyInterest();
        System.out.println("Final balance: " + savingAccount.getBalance());
    }
}

List、Set、Map结构使用

import java.util.*;

public class CollectionExample {
    public static void main(String[] args) {
        List<String> fruits = new ArrayList<>();
        fruits.add("Apple");
        fruits.add("Banana");
        fruits.add("Orange");
        System.out.println("Fruits: " + fruits);

        Set<String> uniqueFruits = new HashSet<>(fruits);
        System.out.println("Unique fruits: " + uniqueFruits);

        Map<String, Integer> fruitPrices = new HashMap<>();
        fruitPrices.put("Apple", 5);
        fruitPrices.put("Banana", 3);
        fruitPrices.put("Orange", 4);
        System.out.println("Fruit prices: " + fruitPrices);
    }
}

高级集合类与操作方法

import java.util.*;

public class AdvancedCollectionExample {
    public static void main(String[] args) {
        List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10);

        long evenNumbersCount = numbers.stream()
                                        .filter(n -> n % 2 == 0)
                                        .count();
        long oddNumbersCount = numbers.stream()
                                      .filter(n -> n % 2 != 0)
                                      .count();

        System.out.println("Even numbers count: " + evenNumbersCount);
        System.out.println("Odd numbers count: " + oddNumbersCount);

        List<String> names = Arrays.asList("Alice", "Bob", "Charlie", "Diana");
        List<String> sortedNames = names.stream()
                                        .sorted()
                                        .collect(Collectors.toList());
        System.out.println("Sorted names: " + sortedNames);
    }
}

Swing基础组件介绍

import javax.swing.*;

public class SwingComponentExample {
    public static void main(String[] args) {
        JFrame frame = new JFrame("Swing Component Example");
        JLabel label = new JLabel("Hello, Swing!");
        label.setSize(200, 50);
        frame.add(label);
        frame.setSize(300, 100);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
    }
}

布局管理器使用与配置

import java.awt.*;
import javax.swing.*;

public class LayoutManagerExample {
    public static void main(String[] args) {
        JFrame frame = new JFrame("LayoutManager Example");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        Container contentPane = frame.getContentPane();
        contentPane.setLayout(new FlowLayout());

        JButton button1 = new JButton("Button 1");
        JButton button2 = new JButton("Button 2");
        JButton button3 = new JButton("Button 3");

        contentPane.add(button1);
        contentPane.add(button2);
        contentPane.add(button3);

        frame.setSize(300, 150);
        frame.setVisible(true);
    }
}

简单GUI应用开发实战

import javax.swing.*;

public class SimpleGUIApp {
    public static void main(String[] args) {
        JFrame frame = new JFrame("Simple GUI Application");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        JLabel label = new JLabel("Welcome to Simple GUI App!");
        JButton button = new JButton("Click Me");

        JPanel panel = new JPanel();
        panel.add(label);
        panel.add(button);

        frame.add(panel);
        frame.setSize(300, 150);
        frame.setVisible(true);
    }
}

输入输出流使用方法

import java.io.*;

public class IOStreamExample {
    public static void main(String[] args) {
        try {
            File file = new File("example.txt");
            BufferedReader reader = new BufferedReader(new FileReader(file));
            String line;
            while ((line = reader.readLine()) != null) {
                System.out.println(line);
            }
            reader.close();

            PrintWriter writer = new PrintWriter(new FileWriter("example.txt", true));
            writer.println("New line added.");
            writer.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

NIO基本概念与文件操作

import java.nio.*;
import java.nio.file.*;
import java.nio.file.attribute.BasicFileAttributes;

public class NIOFileExample {
    public static void main(String[] args) {
        try {
            Path path = Paths.get("example.txt");
            Files.createFile(path);

            ByteBuffer buffer = ByteBuffer.allocate(1024);
            Files.readAllLines(path).forEach(buffer::put);
            Files.write(path, Arrays.asList("Hello, NIO!"), StandardOpenOption.WRITE, StandardOpenOption.TRUNCATE_EXISTING);

            BasicFileAttributes attrs = Files.readAttributes(path, BasicFileAttributes.class);
            System.out.println("File size: " + attrs.size() + " bytes");

            Files.delete(path);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

创建一个完整的JavaSE应用

实战解析与代码实现

创建一个简单的待办事项应用，用户可以添加、删除和查看待办事项。

import java.io.*;
import java.util.ArrayList;
import java.util.Scanner;

public class TodoApp {
    private ArrayList<String> todos = new ArrayList<>();

    public void addTodo(String task) {
        todos.add(task);
        System.out.println("Task added: " + task);
    }

    public void deleteTodo(String task) {
        todos.remove(task);
        System.out.println("Task removed: " + task);
    }

    public void listTodos() {
        if (todos.isEmpty()) {
            System.out.println("No tasks to display.");
            return;
        }
        System.out.println("Todo List:");
        for (String todo : todos) {
            System.out.println(todo);
        }
    }

    public static void main(String[] args) {
        TodoApp app = new TodoApp();
        Scanner scanner = new Scanner(System.in);

        while (true) {
            System.out.println("\nTodo App");
            System.out.println("1. Add Task");
            System.out.println("2. Delete Task");
            System.out.println("3. List Tasks");
            System.out.println("4. Exit");
            System.out.print("Enter choice: ");
            int choice = scanner.nextInt();
            scanner.nextLine();

            switch (choice) {
                case 1:
                    System.out.print("Enter task: ");
                    String task = scanner.nextLine();
                    app.addTodo(task);
                    break;
                case 2:
                    System.out.print("Enter task to delete: ");
                    String taskToRemove = scanner.nextLine();
                    app.deleteTodo(taskToRemove);
                    break;
                case 3:
                    app.listTodos();
                    break;
                case 4:
                    System.out.println("Exiting Todo App.");
                    scanner.close();
                    System.exit(0);
                    break;
                default:
                    System.out.println("Invalid choice.");
            }
        }
    }
}

功能调试

在开发过程中，确保对每个功能进行单元测试，检查是否能正确添加、删除和显示待办事项。

项目部署与发布流程介绍

1. 打包项目：使用Maven或Gradle等构建工具将项目编译并打包成JAR文件。
2. 测试：在不同的环境（如开发、测试、生产）上测试项目，确保功能正常且无明显的性能问题。
3. 发布：通过版本控制系统（如Git）管理发布过程，使用自动化部署工具（如Jenkins、GitLab CI/CD）将JAR文件部署到服务器。
4. 监控：使用性能监控工具（如New Relic、AppDynamics）监控应用的性能和稳定性。
5. 文档：编写详细的用户指南和API文档，帮助用户和开发者正确使用和集成应用。

通过遵循这些步骤，可以确保项目的稳定性和可维护性，同时提高用户满意度。