为什么TreeSet在不相等的情况下删除重复项？ [英] why does TreeSet remove duplicates when they are unequal?

问题描述

朋友，我在使用 TreeSet 获取全部数据时遇到问题。我已经将 TreeSet 排序为相同的值。

Friends, I am having a problem in getting entire data using TreeSet. I have sorted the TreeSet on some same values.

这是我的代码：

MyCars 类：

class MyCars implements Comparable<MyCars>{

    private String number;
    private int yearModel;
    private double horsePower;

    public String getNumber() {
        return number;
    }
    public void setNumber(String number) {
        this.number = number;
    }
    public int getYearModel() {
        return yearModel;
    }
    public void setYearModel(int yearModel) {
        this.yearModel = yearModel;
    }
    public double getHorsePower() {
        return horsePower;
    }
    public void setHorsePower(double horsePower) {
        this.horsePower = horsePower;
    }
    @Override
    public int compareTo(MyCars c) {
        return Double.compare(this.horsePower,c.getHorsePower());
    }
}

SortTest 类：

public class SortTest {

    void GoForSort(){
        Set dataStructure=new TreeSet();

        MyCars c1=new MyCars();
        c1.setNumber("SRT-Viper123");
        c1.setYearModel(2013);
        c1.setHorsePower(450.00);

        MyCars c2=new MyCars();
        c2.setNumber("Chevrolet-Corvette901");
        c2.setYearModel(2012);
        c2.setHorsePower(450.00);

        MyCars c3=new MyCars();
        c3.setNumber("Ford-Mustang678");
        c3.setYearModel(2014);
        c3.setHorsePower(455.00);

        dataStructure.add(c1);
        dataStructure.add(c2);
        dataStructure.add(c3);

        Iterator<MyCars> it=dataStructure.iterator();
        while(it.hasNext()){
            MyCars c=it.next();
            System.out.println(c.getNumber()+"\t"+c.getHorsePower()+"\t"+c.getYearModel());
        }

    }
    public static void main(String[] args) {
        SortTest st=new SortTest();
        st.GoForSort();

    }

}

您可以看到我已经基于horsePower对 TreeSet 进行了排序。而且我给了两个对象相同的马力值。

As you can see I have sorted the TreeSet on the basis of horsePower. And I have given SAME value for horse-power to two objects.

这是我得到的输出：

SRT-Viper123    450.0   2013
Ford-Mustang678 455.0   2014

但是我也希望 Chevrolet-Corvette901 出现在这组输出中。为什么我不明白。

But I also want Chevrolet-Corvette901 to come in this set of output. Why I am not getting it.

有没有办法包含它？因为我发现将集合更改为 ArrayList 时没有问题。 TreeSet 仅排序唯一元素吗？

Is there any way to include that also? Because I found there was NO Problem when I change my collection to ArrayList. Does TreeSet sorts only unique elements?

是否有任何技巧可以获取&在迭代期间打印所有对象，无论它们在 TreeSet ...

Is there any trick to get & print all objects during Iteration regardless of their uniqueness in TreeSet...

推荐答案

您有两个选择：

1. 使您的 compareTo 还会比较 number 和 yearModel 字段。

在每个节点上存储一个集合（数组或 List ）-通常称为 MultiSet 。

Store a collection (array or List) at each node - usually called a MultiSet.

只要您的 compareTo 报告两个项目是相等的，其中只有一个 >将出现在集合中。

So long as your compareTo reports that two items are equal, only one of them will appear in the set.

这篇关于为什么TreeSet在不相等的情况下删除重复项？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！