How to understand java constructor

1. Why constructors should be introduced

Before understanding constructors, we first need to know why constructors are introduced in Java, and the structure function of the device.

Assume that every time we write a class, we must execute an initialize() method. This method reminds you that before using the object, you should first call the initialize() method for initialization. This means that every user can all implement this method. Constructors are introduced in Java to ensure that each object is initialized. Before Java is able to operate the object, the system will automatically call the corresponding constructor to ensure that initialization proceeds.

2. Problems in the naming rules of the constructor

1. The name may conflict with the name of a member variable in the class.

2. It is the responsibility of the compiler to call the constructor, so the compiler must know which method is being called. So Java adopts the method of naming the constructor with the same name as the class.

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3. Use the constructor to perform initialization

The largest constructor The purpose is to perform initialization when creating an object. When an object is created, the system will perform default initialization for the instance of the object. If you want to change this default initialization, you can do it through a custom constructor.

Let’s look at an example of a custom constructor, as follows:

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

    // 这是系统自动提供的构造器public void Person(){}
    // 自定义构造器
    public Person(String name, int age) {
        this.name = name;
        this.age = age;
    }

    public static void main(String[] args) {
        // 使用自定义的构造器创建对象（构造器是创建对象的重要途径）
        Person p = new Person("小明", 12);
        System.out.println(p.age);
        System.out.println(p.name);
    }
}

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