The difference between the effect of the constructor, and the constructor set, get method

First, the definition and role of constructor?

• The method of the class name must be the same name, the constructor does not return type declaration.
• Use the new keyword to instantiate an object when it will automatically call the constructor.
• Java language, at least a default constructor for each class. Once a configuration that defines the display method, the system does not provide a default constructor.

public class People {
    private String name;
    private int age;
    private String sex;
    
    //带参数的构造器
    public People(String name, int age, String sex) {
        this.name = name;
        this.age = age;
        this.sex = sex;
    }
    
    public static void main(String[] args) {
        People people=new People("zhangsan",20,"男");
    }
}

The role of the constructor: used to initialize member variables.

When the new People ( "zhangsan", 20, "male"), the People will call method, the object is initialized.

Two, set and get methods Role:

• When we have used variable value constructor to initialize member, you want to modify a variable, the Zenmo to do it?
• If you re new to an object, it is more occupied by memory. Therefore, we can use the get and set methods to complete.

public class People {
    private String name;
    private int age;
    private String sex;

    //带参数的构造器
    public People(String name, int age, String sex) {
        this.name = name;
        this.age = age;
        this.sex = sex;
    }
    //get方法获取字段
    public int getAge() {
        return age;
    }
    //set方法修改字段
    public void setAge(int age) {
        this.age = age;
    }
    public static void main(String[] args) {
        People people=new People("zhangsan",20,"男");
        people.setAge(22);
        System.out.println(people.getAge());
        System.out.println(people.name);
        System.out.println(people.sex);
    }
}

• For members of the private modified, if you want to use outside the class, so what?
• At this point, if needs to obtain or modify private property, you need to use getter / setter methods.

public class Test {
    public static void main(String[] args) {
        People people=new People("zhangsan",20,"男");
        people.setAge(22);
        System.out.println(people.getAge());
    }
}

methods set and get the role: to modify properties and acquisition; easy to modify, enhance the maintainability of the code; good encapsulation.

Third, the difference between the set and the constructor methods, GET method:

Constructor: used to initialize the object.
set, get method: for member variables to modify, re-assignment; on private property is acquired.