TreeMap图书馆案例

package tushu;

import java.util.Comparator;
import java.util.TreeMap;

public class TreeMapTest {

    public static void main(String[] args) {
          TreeMap<String,Book> map=new TreeMap<String,Book>(new MyComparator());
        map.put("B45678", new Book("B45678","钢铁是怎样连城的","保尔",56));
        map.put("B678", new Book("B678","世界时平的","保尔",56));
        map.put("D89", new Book("D89","java编程思想","kobe",56));
        map.put("A15678", new Book("A15678","高等数学","joms",56));
        System.out.println(map);

    }

}
 class Book {

    String bookno;
    String bookName;
    String author;
    int price;
    public String getBookno() {
        return bookno;
    }
    public void setBookno(String bookno) {
        this.bookno = bookno;
    }
    public String getBookName() {
        return bookName;
    }
    public void setBookName(String bookName) {
        this.bookName = bookName;
    }
    public String getAuthor() {
        return author;
    }
    public void setAuthor(String author) {
        this.author = author;
    }
    public int getPrice() {
        return price;
    }
    public void setPrice(int price) {
        this.price = price;
    }
    @Override
    public String toString() {
        return "Book [bookno=" + bookno + ", bookName=" + bookName
                + ", author=" + author + ", price=" + price + "]";
    }
    public Book(String bookno, String bookName, String author, int price) {
        super();
        this.bookno = bookno;
        this.bookName = bookName;
        this.author = author;
        this.price = price;
    }

}
class MyComparator implements Comparator<String>{

    @Override
    public int compare(String o1, String o2) {
        if(o1.length()==o2.length()){
            return o1.compareTo(o2);
        }
        return o1.length()-o2.length();
    }

}