java - Arraylist 输出被覆盖

Question

这个问题已经有答案了:

Avoiding overwriting objects in ArrayList (2 个回答)

已关闭 4 年前。

之前存储在数组列表中的数据正在被更新的数据替换。

代码如下

public class Telivision {

    private String tvBrand;
    private Double tvCost;
    private Integer tvDimension;
    private String tvScreen;
    public String getTvBrand() {
        return tvBrand;
    }
    public void setTvBrand(String tvBrand) {
        this.tvBrand = tvBrand;
    }
    public Double getTvCost() {

        return tvCost;
    }
    public void setTvCost(String brand) {
        if(this.tvBrand.equalsIgnoreCase("Samsung")){
            this.tvCost = 100*1.5;
        }else if(this.tvBrand.equalsIgnoreCase("Sony")){
            this.tvCost = 100*2.0;
        }
    }
    public Integer getTvDimension() {
        return tvDimension;
    }
    public void setTvDimension(Integer tvDimension) {
        this.tvDimension = tvDimension;
    }
    public String getTvScreen() {
        return tvScreen;
    }
    public void setTvScreen(String tvScreen) {
        this.tvScreen = tvScreen;
    }
    @Override
    public String toString() {
        return "Telivision [tvBrand=" + tvBrand + ", tvCost=" + tvCost + ", tvDimension=" + tvDimension + ", tvScreen="
                + tvScreen + "]";
    }

测试仪如下图

public class TelivisionTester {

    public static void main(String[] args) {

        Telivision telivision = new Telivision();
        ArrayList<Telivision> telList = new ArrayList<Telivision>();        
        telivision.setTvBrand("SAMSUNG");
        telivision.setTvDimension(40);
        telivision.setTvScreen("Led");
        telivision.setTvCost("Samsung");
        telList.add(telivision);
        System.out.println(telList);
        System.out.println(telivision.getTvBrand()+"Cost is "+telivision.getTvCost());

        telivision.setTvBrand("Sony");
        telivision.setTvDimension(36);
        telivision.setTvScreen("Led");
        telivision.setTvCost("Sony");
        telList.add(telivision);
        System.out.println(telList);
        System.out.println(telivision.getTvBrand()+"Cost is "+telivision.getTvCost());
    }

预期的输出如下所示

[Telivision [tvBrand=SAMSUNG, tvCost=150.0, tvDimension=40, tvScreen=Led],
Telivision [tvBrand=Sony, tvCost=200.0, tvDimension=36, tvScreen=Led]]

但观察到的输出如下所示

[Telivision [tvBrand=Sony, tvCost=200.0, tvDimension=36, tvScreen=Led], 
Telivision [tvBrand=Sony, tvCost=200.0, tvDimension=36, tvScreen=Led]]

请让我知道我在这段代码中犯了什么错误

Answer 1

您的列表未被覆盖。您将添加该类的同一实例两次，而不是使用新属性创建一个新实例。由于原始实例已更改，因此列表中的两个条目将获得相同的属性。为添加到列表中的每台电视创建一个新的对象实例。

   public static void main(String[] args) {

    Telivision telivision = new Telivision();
    ArrayList<Telivision> telList = new ArrayList<Telivision>();        
    telivision.setTvBrand("SAMSUNG");
    telivision.setTvDimension(40);
    telivision.setTvScreen("Led");
    telivision.setTvCost("Samsung");
    telList.add(telivision);
    System.out.println(telList);
    System.out.println(telivision.getTvBrand()+"Cost is "+telivision.getTvCost());
    Telivision secondTelivision = new Telivision();
    secondTelivision.setTvBrand("Sony");
    secondTelivision.setTvDimension(36);
    secondTelivision.setTvScreen("Led");
    secondTelivision.setTvCost("Sony");
    telList.add(secondTelivision);
    System.out.println(telList);


}