Java中的构造方法(构造函数)与普通方法区别及说明

 //Test（"a"）；其中这个就是构造函数，“a”为构造方法的形参；

public static void main(String[] args) {
        Phone p1 = new Phone();
        p1.show();
        
        System.out.println("----------------");
        
        Phone p2 = new Phone("vivoxplay5",2999);
        p2.show();
    }        
}

class Phone{
    private String brand;  //品牌
    private int price;       //价格
    
    //无参构造方法
    public Phone(){
        System.out.println("无参构造");
    }

    //有参构造器
    public Phone(String brand, int price) {
        this.brand = brand;
        this.price = price;
        System.out.println("有参构造");
    }
    
    public void show(){
        System.out.println(brand+"..."+price);
    }

    
}

/**
     * 无参构造方法：给属性进行初始化
     * set/get方法：修改属性值
     * @param args
     */
public static void main(String[] args) {
        //无参构造创建对象
        Phone p1 = new Phone();    
        p1.setBrand("vivoxplay5");
        p1.setPrice(2999);
        
        p1.setBrand("vivo");
        p1.show();
        
        System.out.println("----------------");
        //有参构造创建对象
        Phone p2 = new Phone("vivoxplay5",2999);
        //这种方式并不是改名，而是将原对象变成垃圾
        //p2 = new Phone("vivo",2000);
        p2.show();
    }        
}

class Phone{
    private String brand;  //品牌
    private int price;       //价格
    
    public String getBrand() {
        return brand;
    }

    public void setBrand(String brand) {
        this.brand = brand;
    }

    public int getPrice() {
        return price;
    }

    public void setPrice(int price) {
        this.price = price;
    }

    //无参构造方法
    public Phone(){
        System.out.println("无参构造");
    }

    //有参构造器
    public Phone(String brand, int price) {
        this.brand = brand;
        this.price = price;
        System.out.println("有参构造");
    }
    
    public void show(){
        System.out.println(brand+"..."+price);
    }

    
}

public void driverCar (int a,double b) {
    speed= 50;
    direction= "南方";
}

public class Student{
public  Student(){                    //无参构造方法

System.out.println("无参方法被调用")；

}

}

public class Test {
public  static void main (String[]  args){
Student   stu = new Student();  //实例化Student对象

}

}//该方法是无参的构造方法，即构造方法不接收参数，执行后输出即可，无参的构造方法被调用。

public class Student{
private String name;
private int  age;
public  Student(String name,int age){             //有参构造方法
    this.name = name;
    this.age  = age ;
}
public  void show (){
System.out.println("姓名："+name+"年龄："+age)；
}
}
public  class  Test02(){
public static void main (String[]   args)
{
Student  stu = new Student("王小五"，25)；     //实例化对象的同时赋值
stu.show();
}
}

public static int sum (int a , int b)
{
    int c = a+b;
    return c ;
}
public static void main(String[] args)
{
           //sum(10,20); //单独调用
           //System.out.println(sum(10,20));  //输出调用
           int sum01 =sum(10,20); //赋值调用
}