[問題] 有關comparable 中判斷式的問題?

[spiderman007 (千里之外)]

import java.util.*;
class Book implements Comparable<Book>{
        String name;
        Double price;
        public Book(String s, double p){
                this.name=s;
                this.price=p;
        }


        public int compareTo(Book obj){
    ->          if((this.price) == (obj.price) ){
    ->    //    if((this.price - obj.price) == 0){
                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
                上下兩行的比較? 有不同嗎? 為何上行印出的資料少一筆呢?
                        return this.name.compareTo(obj.name);
                }

                return this.price.compareTo(obj.price);

        }

        public void show(){
                System.out.println(name);
                System.out.println(price);
        }
}

class TreeSetEx{
        public static void main(String[] args){
                TreeSet<Book> tset = new TreeSet<Book>();

                Book book2 = new Book("SCJP認証手冊",600.0);
                Book book3 = new Book("VB2008程式設計",600.0);
                Book book1 = new Book("Java程式手冊",580.0);

                tset.add(book1);
                tset.add(book2);
                tset.add(book3);

                System.out.println("書籍資訊如下:");
                System.out.println("---------------------------");
                for(Book b : tset){
                        b.show();
                        System.out.println("---------------------------");
                }


        }
}

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