Introduction to Java Basics to Practical Applications: In-depth Analysis of Practical Cases

Question: How to build practical applications using Java? Solution: Master the basic syntax of Java, including variables, types, objects and classes. Understand specific applications through practical cases, such as student management systems. Use Java collection framework to manage and process data, such as supermarket shopping system. Master Java IO streams for file reading and writing, such as file reading and writing systems.

Java Basics to Practical Application: In-depth Analysis of Practical Cases

Foreword: Java is a A powerful object-oriented programming language that is widely used in various fields. From beginners to experienced developers, this article aims to explain the basic knowledge of Java in a simple and easy-to-understand manner through practical cases, and guide you to apply it in actual development scenarios.

1. Basics of Java syntax

1. Basic syntax: variables, types, operators and control flow
2. Objects and classes: creation and Using classes, encapsulation, inheritance and polymorphism

2. Practical case: student management system

1. Problem description: Design and implement a system for managing student information, including adding, deleting, querying and modifying student information.

2. Implementation plan:

   • Create the Student class, including student name, student number and score information
   • Create the StudentManager class, Implement methods to add, delete, query and modify student information
   • Create a StudentManager instance in the Main class and use its methods to operate student information

Code example:

// Student类
public class Student {
    private String name;
    private String id;
    private int score;

    // getter 和 setter 方法
}

// StudentManager类
public class StudentManager {
    private List<Student> students;

    // 添加学生方法
    public void addStudent(Student student) {
        // ...
    }

    // 删除学生方法
    public void deleteStudent(String id) {
        // ...
    }

    // 查询学生方法
    public Student queryStudent(String id) {
        // ...
    }

    // 修改学生方法
    public void updateStudent(Student student) {
        // ...
    }
}

// Main类
public class Main {
    public static void main(String[] args) {
        StudentManager studentManager = new StudentManager();

        // 添加学生
        studentManager.addStudent(new Student("John", "123", 90));

        // 查询学生
        Student john = studentManager.queryStudent("123");

        // 修改学生
        john.setScore(95);

        // ...
    }
}

3. Java collection framework

1. Overview of collections: List, Set and Map
2. Common operations : Add, delete, query and traverse
3. Generic collections: Collection and Map

Practical case: Supermarket shopping system

1. Problem Description:Design and implement a supermarket shopping system that can add and delete products and calculate the total amount.

2. Implementation plan:

   • Use Set to store product information to ensure that the products are not repeated
   • Use Map to store product quantity, To calculate the total amount

Code example:

import java.util.HashSet;
import java.util.HashMap;

// Item类
public class Item {
    private String name;
    private double price;

    // getter 和 setter 方法
}

// ShoppingCart类
public class ShoppingCart {
    private Set<Item> items;
    private Map<Item, Integer> quantities;

    // 添加商品方法
    public void addItem(Item item, int quantity) {
        // ...
    }

    // 删除商品方法
    public void removeItem(Item item) {
        // ...
    }

    // 计算总金额方法
    public double getTotalAmount() {
        // ...
    }
}

// Main类
public class Main {
    public static void main(String[] args) {
        ShoppingCart shoppingCart = new ShoppingCart();

        // 添加商品
        shoppingCart.addItem(new Item("Apple", 1.5), 2);
        shoppingCart.addItem(new Item("Banana", 1), 3);

        // 计算总金额
        double totalAmount = shoppingCart.getTotalAmount();

        // ...
    }
}

4. Java IO flow

1. Stream Overview: Input Stream and Output Stream
2. Byte Stream: FileInputStream and FileOutputStream
3. Character Stream: FileReader and FileWriter

Practical case: File reading and writing system

1. Problem description:Design and implement a file reading and writing system that can read and write text files.

2. Implementation plan:

   • Use FileReader to read text files and obtain text content line by line
   • Use FileWriter to write Text file and write the text in lines

Code example:

import java.io.FileReader;
import java.io.FileWriter;

// FileManager类
public class FileManager {
    // 读取文本文件方法
    public String readTextFile(String fileName) {
        // ...
    }

    // 写入文本文件方法
    public void writeTextFile(String fileName, String content) {
        // ...
    }
}

// Main类
public class Main {
    public static void main(String[] args) {
        FileManager fileManager = new FileManager();

        // 读取文本文件
        String content = fileManager.readTextFile("test.txt");

        // 写入文本文件
        fileManager.writeTextFile("test.txt", content + "\nNew content");

        // ...
    }
}

The above is the detailed content of Introduction to Java Basics to Practical Applications: In-depth Analysis of Practical Cases. For more information, please follow other related articles on the PHP Chinese website!