[英]How to organise alphabetically an array of objects in Java
I am trying to simulate a library of Albums.我正在尝试模拟专辑库。 But I would also be able to organise the contents of the library alphabetically by the author's name.
但我也可以按作者姓名的字母顺序组织图书馆的内容。 Any help in how to organise the contents of the array of objects alphabetically?
如何按字母顺序组织对象数组的内容有什么帮助?
I have created a Class called Album, which I use to create my objects我创建了一个名为 Album 的类,我用它来创建我的对象
public class Album {
private String author;
private String name;
private String year;
public Album(String a, String n, String y) { // constructor
author = a;
name = n;
year = y;
}
public String toString()
{
return author +","+ name + "," + year;
}
}
The class Collection is used to store the objects into an array类 Collection 用于将对象存储到数组中
public class AlbumCollection {
public Album collection[]= new Album[10];
private int numAlbums = 0;
public void add (Album a){
if (numAlbums >= collection.length){
Album newcollection[]= new Album [collection.length * 2];
for (int n = 0; n < numAlbums; n ++){
newcollection[n] = collection[n];
}
newcollection = collection;
}
collection[numAlbums] = a;
numAlbums = numAlbums + 1;
}
public String toString()
{
String details = "";
for ( int p = 0; p < collection.length ; p ++)
{
details = details + collection[p] + "\n" ;
}
details += "\n";
return details;
}
}
This is the class that I am using to create the Album Objects这是我用来创建相册对象的类
public class TestCollection {
public static void main(String[] args) {
AlbumCollection c = new AlbumCollection();
c.add( new Album("DaftPunk","Discovery","2001"));
c.add( new Album ("Pink Floid","The Dark Side Of The Moon","1973"));
c.add( new Album( "The Clash", "London Calling", "1979"));
System.out.print(c);
}
}
I had to change the compareTo method to sort by the author.我不得不更改 compareTo 方法以按作者排序。
public class Album {
private String author;
private String name;
private String year;
public Album(String a, String n, String y) { // constructor
author = a;
name = n;
year = y;
}
public String toString()
{
return author +","+ name + "," + year;
}
public int compareTo(Album a) {
// usually toString should not be used,
// instead one of the attributes or more in a comparator chain
return author.compareTo(a.author);
}
} And i added method sort to sorting elements of array:我添加了方法 sort 来对数组元素进行排序:
public class Collection {
public Album collection[]= new Album[10];
private int numAlbums = 0;
public void Add (Album a){
if (numAlbums >= collection.length){
Album newcollection[]= new Album [collection.length * 2];
for (int n = 0; n < numAlbums; n ++){
newcollection[n] = collection[n];
}
newcollection = collection;
}
collection[numAlbums] = a;
numAlbums = numAlbums + 1;
}
public String toString()
{
String details = "";
for ( int p = 0; p < numAlbums ; p ++)
{
details = details + collection[p] + "\n" ;
}
details += "\n";
return details;
}
public void sort(){
for(int i=0;i<numAlbums;i++){
for(int j=i;j<numAlbums-1;j++){
if(collection[j].compareTo(collection[j+1])>0){
Album tmp =collection[j];
collection[j]=collection[j+1];
collection[j+1]=tmp;
}
}
}
}
} }
You can not use the length of an array, if you store the number of authors, because you will print null values如果存储作者数,则不能使用数组的长度,因为您将打印空值
public static void main(String[] args) {
Collection c = new Collection();
c.Add( new Album("DaftPunk","Discovery","2001"));
c.Add( new Album ("Pink Floid","The Dark Side Of The Moon","1973"));
c.Add( new Album( "The Clash", "London Calling", "1979"));
c.sort();
System.out.print(c);
}
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