ArrayList<class>交换方法 [英] ArrayList&lt;class&gt; swap method

问题描述

  public void sortDatabase(){
        for(int j=0;j<productDatabase.size()-1;j++){
        for(int i =0;i<productDatabase.size()-j-1;i++){
    if(compareTo(i)){
        Collections.swap(productDatabase,i,i++ );  //Με την Χρήση της Collections βιβλιοθήκης κάνω SWAP! Πρέπει να βάλω την βιβλιοθήκη όμως!

    }


    }
    }
}

public boolean compareTo(int index){

    if(productDatabase.get(index).getPrice() > productDatabase.get(index++).getPrice()){
        return true;
    }
    else
        return false;



}

上次我以非常糟糕的方式发布了我的答案.对不起，我的英语真的很烂，但这是我的问题.我已经声明了一个 ArrayList <产品类 > productDatabase .产品类中有一些字段.主要问题是我无法对 productDatabase 元素进行排序.

Last time i posted my answer in a very bad way. Sorry for my english that really suck , but here is my problem. I 've declared an ArrayList < class of Product > productDatabase . Product class has some fields in it. The main problem is that i cannot sort my productDatabase elements .

我使用 Collections.swap() 但即使我的 ArrayList 由另一个对象的元素组成，我也可以使用该方法吗?

I use Collections.swap() but can i use that method even if my ArrayList consists of elements that are another object ?

另外，我想让你看看我写的 compareTo 方法，它是布尔值并返回一个值以了解是否需要交换元素.

Also i want you to take a look at my compareTo method that i wrote which is boolean and returns me a value to know if swap of elements is needed.

提前致谢......并对我最近的第一篇糟糕的帖子感到抱歉.

Thanks in advance ... and feeling sorry for my latest first bad post.

推荐答案

无需通过使用 swap() 实现排序算法来重新发明轮子.Collections 已经提供了一个 sort() 方法，它使用了一个很好的归并排序实现.

There's no need to reinvent the wheel by implementing sorting algorithms using swap(). Collections already provides a sort() method using a nice implementation of mergesort.

实施Comparator 并使用 Collections.sort(List, Comparator) 对List进行排序自定义比较标准.

Implement a Comparator<Product> and use Collections.sort(List<T>, Comparator<T>) to sort the List according to a custom comparison criteria.

Comparator<Product> PRICE_COMPARATOR = new Comparator<Product>() { 
    @Override
    public int compare(Product o1, Product o2) {
        // Check for nulls if necessary
        return o1.getPrice().compareTo(o2.getPrice());
    }
}

List<Product> sortedList = Collections.sort(unsortedList, PRICE_COMPARATOR);

如果您的 List 不是 List，而是 List