java - 如何在不覆盖以前的副本的情况下将对象添加到类中的 ArrayList

Question

尝试创建更多的汽车实例，但是当我将它们添加到数组时，它们会覆盖之前的实例，这是因为 ArrayList 在我创建的每个实例中，创建一个具有ArrayList 来容纳一切？

import java.util.ArrayList;

public class Automobile {

private String make;
private String color;
private int year;
private int mileage;
private ArrayList<Automobile> autoArray = new ArrayList<>();

public Automobile(String make, String color, int year, int mileage) {
    this.make = make;
    this.color = color;
    this.year = year;
    this.mileage = mileage;
    autoArray.add(this);


}

//setters (mutators)
public void setYearModel(int y) {
    year = y;
}

public void setMake(String type) {
    make = type;
}

public void setColor(String col) {
    color = col;
}

public void setMileage(int miles) {
    mileage = miles;
}

public String toString() {
    return "test = " + color + "; test " + year + "; test " + year + "; test " + make;
}


private ArrayList addVehicle(String m, String c, int y, int mile) {
    this.make = m;
    this.color = c;
    this.year = y;
    this.mileage = mile;
    autoArray.add(this);
    return autoArray;
 }
    public static void main(String[] args) {

    Automobile cars = new Automobile("kelvin","luke", 6, 9 );
    cars.autoArray.forEach(System.out::println);
    cars.addVehicle("horny","luke", 6, 9 );
    cars.autoArray.forEach(System.out::println);
}

Answer 1

您需要创建一个新的 Automobile在 addVehicle()而不是修改现有的:

private ArrayList addVehicle(String m, String c, int y, int mile) {
    autoArray.add(new Automobile(m, c, y, mile));
    return autoArray;
}

这应该可以解决您的问题。但是，是的，理想情况下，您还应该按照其他评论者的建议重构您的代码，因为创建 ArrayList<Automobile> 没有意义。在 Automobile 的每个实例中.