您可以提供一个Comparator来比较您想要的任何类型，Comparable或其他类型。
对于数组和集合，您使用

Arrays.sort(array, myComparator);
Collections.sort(list, myComparator);

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甚至像TreeSet这样的排序集合也可以使用自定义的Comparator
例如

Collections.sort(books, new Comparator<Book>() {
   public int compare(Book b1, Book b2) {
      return if b1 is greater return +1, if b2 is smaller return -1 otherwise 0
   }
});

型

如果你可以使用Comparators，为你需要的每种排序类型写一个，例如，升序为书名，降序为页码。如果第一个参数大于第二个参数，Comparator的compare方法必须返回正数，如果第一个参数小于第二个参数，则返回负数，如果它们相等，则返回零。

import java.util.Comparator;
import java.util.List;
import java.util.Arrays;
class Book{
    String title;
    int pageNumber;
    public Book(String title, int pageNumber){
        this.title = title;
        this.pageNumber = pageNumber;
    }
    String getTitle(){ return title; }
    int getPageNumber(){ return pageNumber; }
    public String toString(){
        return "(" + title + ", " + pageNumber + " pages)";
    }
}
public class Library{
    // These variables are static because you don't need multiple copies
    // for sorting, as they have no intrinsic state.
    static private Comparator<Book> ascTitle;
    static private Comparator<Book> descPageNumber;
    // We initialize static variables inside a static block.
    static {
        ascTitle = new Comparator<Book>(){
            @Override
            public int compare(Book b1, Book b2){
                return b1.getTitle().compareTo(b2.getTitle());
            }
        };
        descPageNumber = new Comparator<Book>(){
            @Override
            public int compare(Book b1, Book b2){
                // Java 7 has an Integer#compare function
                return Integer.compare(b1.getPageNumber(), b2.getPageNumber());
                // For Java < 7, use 
                // Integer.valueOf(n1).compareTo(n2);
                // DO NOT subtract numbers to make a comparison such as n2 - n1.
                // This can cause a negative overflow if the difference is larger 
                // than Integer.MAX_VALUE (e.g., n1 = 2^31 and n2 = -2^31)
            }
        };
    }
    private Book[] books;
    public Book[] getBooks(){ return books; }
    public void sortAscTitle(){
        Arrays.sort(books, ascTitle);
    }
    public void sortDescPageNumber(){
        Arrays.sort(books, descPageNumber);
    }
    public Library(Book[] books){
        this.books = books;
    }
    public static void main(String[] args){
        Library library = new Library( new Book[]{
            new Book("1984", 123), 
            new Book("I, Robot", 152), 
            new Book("Harry Potter and the Philosopher's Stone", 267),
            new Book("Harry Potter and the Goblet of Fire", 759),
            new Book("The Bible", 1623)
        });
        library.sortAscTitle();
        System.out.println(Arrays.toString(library.getBooks()));
        library.sortDescPageNumber();
        System.out.println(Arrays.toString(library.getBooks()));
    }
}

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把这个放在你的图书馆里：

java.util.Collections.sort(bookList, bookComparator);

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扩展@PeterLawrey对Java 8的回答，现在可以使用Lambda Expression而不是Comparable<T>委托：

Collections.sort(books, (firstBook, secondBook -> b1 is greater return +1, 
                                                  if b2 is smaller return -1 otherwise 0));

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