java - java中带输入的多个构造函数的基本用法

Question

尽管对构造函数进行了研究，但我还是无法理解它们，非常感谢一些帮助和解释。

我的目标是让用户输入汽车的“品牌”和“型号”，我希望将输入分配给构造函数中的每个变量，然后再拥有三辆不同的汽车。

如何正确有效地设置一个“make”变量，该变量分配给用户输入并可以使用构造函数进行访问以进行显示。这是非常基本的，但我在编码时遇到了困难。

package cartest;

import java.util.Scanner;

public class CarTest 
//make, model, year, price, color, size
//default constructor
//property assignment constructor
//enter three diferent cars and display final information
//toString() method and a method to honk the horn
{
    String make;
    String model;
    int year;
    int price;
    String color;
    String size;

    public CarTest()
    {

    }

    void setMake(String make)
    {
        Scanner scanner = new Scanner (System.in);
        System.out.println("Please enter a make:");
        make = scanner.nextLine();
    }

    void getMake()
    {
        System.out.println("Selected make: " + make);
    }
    void setModel(String model)
    {
        Scanner scanner = new Scanner (System.in);
        System.out.println("Please enter a model:");
        model = scanner.nextLine();
    }



    public static void main(String[] args) 
    {

        CarTest carOne = new CarTest(); 
        carOne.getMake();



    }


}

Answer 1

I'm aiming to have the user input a "make" and a "model" for a car, I would like the assignment of input to each variable in a constructor, and later on have three different cars.

我对你的类(class)做了一些修改，如下所示:

class CarTest {
    private String make;
    private String model;
    private int year;
    private int price;
    private String color;
    private String size;

    public CarTest() {
        this.make = "somevalue";
        this.model = "somevalue";
        this.year = 2017;
        this.price = 50000;
        this.color = "somecolor";
        this.size = "somesize";
    }

    public CarTest(String make, String model){
        this.make = make;
        this.model = model;
    }


    public String getMake() {
       return make;
    }

    public void setMake(String make) {
       this.make = make;
    }

    public String getModel() {
       return model;
    }

    public void setModel(String model) {
       this.model = model;
    }

    public int getYear() {
       return year;
    }

    public void setYear(int year) {
       this.year = year;
    }

    public int getPrice() {
       return price;
    }

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

    public String getColor() {
       return color;
    }

    public void setColor(String color) {
       this.color = color;
    }

    public String getSize() {
       return size;
    }

    public void setSize(String size) {
       this.size = size;
    }

    @Override
    public String toString() {
    return "CarTest{" +
            "make='" + make + '\'' +
            ", model='" + model + '\'' +
            ", year=" + year +
            ", price=" + price +
            ", color='" + color + '\'' +
            ", size='" + size + '\'' +
            '}';
    }
}

正如您所看到的，有一个默认构造函数，您可以在其中指定对象的默认值，还有一个带有两个参数的构造函数，允许您设置 make 和 model 在对象构造时，如果您认为有必要，当然可以扩展参数。

我建议将 main 方法分离到不同的类中并让它执行此功能:

public static void main(String[] args) {
      Scanner scanner = new Scanner (System.in);
      System.out.println("Please enter a model:");
      String model = scanner.nextLine(); // validate if you need to
      System.out.println("please enter a make");
      String make = scanner.nextLine();  // validate if you need to
      CarTest carOne = new CarTest(make,model); // pass the entered details to the carOne object
      System.out.println(carOne.getMake()); // will display the value of make that has been entered
}

我已经为你完成了一半的任务:

//make, model, year, price, color, size
//default constructor
//property assignment constructor
//enter three diferent cars and display final information
//toString() method and a method to honk the horn

您只需在我提供的解决方案中添加一些额外的代码，然后就可以开始了。