How to write a class in Java?

To write a Java class, follow these steps: 1. Define the class name: Use the keyword “class” followed by the class name to define a class. The class name should start with a capital letter and follow camel case naming convention.

public class MyClass {
    // 类的内容在这里定义
}

Defining member variables in a class: Within a class, member variables can be defined to store the object’s state. They can be of any data type and can have different access modifiers (public, private, protected) to control access.

public class MyClass {
    private int myVariable; // 私有成员变量，只能在类内部访问
    public String myString; // 公共成员变量，可以在任何地方访问
}

Define the constructor of a class: The constructor is used to create objects of the class and initialize the object’s member variables. The constructor has the same name as the class.

public class MyClass {
    private int myVariable;
    public MyClass(int variable) {
        myVariable = variable;
    }
}

Defining methods in classes: Methods can be defined within a class to perform specific operations. A method has a return type, method name, and parameter list. Methods can have different access modifiers and can also be static methods.

public class MyClass {
    private int myVariable;
    public MyClass(int variable) {
        myVariable = variable;
    }
    
    public void myMethod() {
        System.out.println("This is my method");
    }
    
    public int getMyVariable() {
        return myVariable;
    }
}

Use of class: Classes that have been written can be used in other classes. First, an object of the class needs to be created, and then the methods of the object can be called and the member variables of the object can be accessed.

public class Main {
    public static void main(String[] args) {
        MyClass myObject = new MyClass(10); // 创建类的对象
        myObject.myMethod(); // 调用对象的方法
        int variable = myObject.getMyVariable(); // 访问对象的成员变量
    }
}

These are the basic steps for writing a simple Java class. Of course, there are many other syntax rules, design patterns, and best practices to learn and master.