java - 使用自定义比较器将对象添加到二叉搜索树？

Question

我需要将对象添加到二叉搜索树并想编写自己的 compareTo 方法。我该怎么做。实际上我正在尝试实现自定义 TreeSet。我很困惑在哪里实现比较器或可比较并定义它。任何帮助表示赞赏

Answer 1

请参考以下代码

package com.example.treeset;

    import java.util.Comparator;
    import java.util.TreeSet;

    public class MyCompUser {

        public static void main(String a[]){
            //By using name comparator (String comparison)
            TreeSet<Empl> nameComp = new TreeSet<Empl>(new MyNameComp());
            nameComp.add(new Empl("Ram",3000));
            nameComp.add(new Empl("John",6000));
            nameComp.add(new Empl("Crish",2000));
            nameComp.add(new Empl("Tom",2400));
            for(Empl e:nameComp){
                System.out.println(e);
            }
            System.out.println("===========================");
            //By using salary comparator (int comparison)
            TreeSet<Empl> salComp = new TreeSet<Empl>(new MySalaryComp());
            salComp.add(new Empl("Ram",3000));
            salComp.add(new Empl("John",6000));
            salComp.add(new Empl("Crish",2000));
            salComp.add(new Empl("Tom",2400));
            for(Empl e:salComp){
                System.out.println(e);
            }
        }
    }

    class MyNameComp implements Comparator<Empl>{

        @Override
        public int compare(Empl e1, Empl e2) {
            return e1.getName().compareTo(e2.getName());
        }
    }   

    class MySalaryComp implements Comparator<Empl>{

        @Override
        public int compare(Empl e1, Empl e2) {
            if(e1.getSalary() > e2.getSalary()){
                return 1;
            } else {
                return -1;
            }
        }
    }

    class Empl{

        private String name;
        private int salary;

        public Empl(String n, int s){
            this.name = n;
            this.salary = s;
        }

        public String getName() {
            return name;
        }
        public void setName(String name) {
            this.name = name;
        }
        public int getSalary() {
            return salary;
        }
        public void setSalary(int salary) {
            this.salary = salary;
        }
        public String toString(){
            return "Name: "+this.name+"-- Salary: "+this.salary;
        }
    }

Answer 2

您要确保添加到TreeSet工具的对象Comparable。这意味着确保存储的对象实现JavadoccompareTo中定义的方法。

您可能不需要Comparator.

顺便说一句，我们最近创建了一个关于这个主题的教程。希望它可以帮助你。

Answer 3

对于 a TreeSet，您需要给出自己的Comparator接口实现。

像这样的东西，也许？

// Using an anonymous interface
Set<Foobar> example = new TreeSet<Foobar>(new Comparator<Foobar>() {
  @Override
  public int compare(Foobar f1, Foobar f2) {
    // How will you compare f1 and f2??
    return 0;
  }

  @Override
  public boolean equals(Object obj) {
    // How will you determine if objects are equal?
    return false;
  }
}
);

Answer 4

您的对象必须实现接口 Comparable

class MyClass implements Comparable { 
  int compareTo(){...}
}
final Set set = new TreeSet();
set.add(new MyClass());
....
set.add(new MyClass());

或制作我们自己的比较器：

class MyClass {}

class MyComparator implements Comparator {
    int compareTo(Object o1, Object o2){
      ...
    }
}
final Set set = new TreeSet(new MyComparator());
set.add(new MyClass());
....
set.add(new MyClass());