java 中 LinkedList 迭代中的 LinkedList

Question

我正在尝试在链表中迭代链表，但我不确定如何进行。我习惯于将传递的参数用于将要迭代的内容，但是当我在链表中迭代链表并计划迭代直到找到与传递的虚拟对象匹配的记录时。

这是我正在尝试做的一个例子

private static boolean addSongFromAlbumToAlbum(LinkedList<Album> albums1, LinkedList<Song> targetAlbum,
                                             String title){
//creating a dummy song for comparison of title parameter with arbitrary time duration.
        Song dummySong = new Song(title, 000);

        ListIterator<Album> album1ListIterator = albums1.listIterator();
        ListIterator<Song> targetAlbumListIterator = targetAlbum.listIterator();

        //nested album iterator
        ListIterator<Song> nestedAlbumInAlbum = nestedAlbum.listIterator();

        //checking whether the song with the "title" parameter entered exists in the LinkedList
        //of albums
        while(album1ListIterator.hasNext()){

            while(nestedAlbumInAlbum.hasNext()){

                //checking if current iteration has an object with same value for title as title parameter.

                Song comparisonSongToAdd = nestedAlbumInAlbum.next();
                int comparisonValue = comparisonSongToAdd.getTitle().compareTo(title);
                if(comparisonValue ==0){

                    //check whether the found object already exists in the album
                    while (targetAlbumListIterator.hasNext()){
                        SongComparator comparator = new SongComparator(); //create new comparator object to compare

                        int comparatorValue = comparator.compare(comparisonSongToAdd, targetAlbumListIterator.next());
                        if (comparatorValue == 0) {
                            System.out.println(comparisonSongToAdd + " already exists in the Album. please choose\n a different song.");
                            return false;

                        }//end if comparator

                    }//end target album while
                    targetAlbumListIterator.add(comparisonSongToAdd);

                }//end if song title found

            }//end nested album while
        }//end albums while iterator
        return true;

    }//end addSongFromAlbum method

///这里是SongComparatorclass

public class SongComparator implements Comparator<Song> {

    public int compare(Song song1, Song song2){
        if(song1.getTitle() == song2.getTitle() && song1.getDurationSeconds() == song2.getDurationSeconds()){
            return 0;
        }else{
            return -1;
        }
    }

}

我应该如何在没有参数的情况下在相册的 LinkedList 中迭代 LinkedList？如果它需要一个参数，考虑到它会随着外部 while 循环的每次迭代而改变，我应该如何确定该参数的用途。

Answer 1

您可以使用 java 8 个流，而不是创建迭代器，

要查找相册 1 和相册 2 中的内容，请使用：

    albums1.forEach(album1Element -> {
        //keeps only what returns true in the filter.
        List<Song> listOfSongsToAdd = targetAlbum.filter(song -> song.compareTo(title)).collect(Collectors.toList);
        listOfSongsToAdd.forEach(songToAdd -> {
           ...

        });

    });

Answer 2

检查下面的代码行。这里，next() returns 是一个 Song 对象，而 title 是一个 String 对象。这两者不能相提并论。您可能必须调用 nestedAlbumInAlbum.next() 并将对象存储在 Song 引用变量中，然后将 song.getTitle() 与 title.

进行比较

int comparisonValue = nestedAlbumInAlbum.next().compareTo(title);

此外，您多次呼叫 nestedAlbumInAlbum.next()。 1 个实例在上面，另一个实例在 if 条件内。您应该限制只调用一次 next() 方法进行迭代。每次调用 nestedAlbumInAlbum.next() 时，它都会 returns 下一个 Song 对象。

java 中 LinkedList 迭代中的 LinkedList

LinkedList inside a LinkedList iteration in java

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linked-list

object

comparator