Java 挽救的比较器(Comparator)

·如果在不能修改Book类定义的情况下是不可能使用Comparable接口的，为此Java提供了另一个比较器java.util.Comparator接口下两个方法:public interface Comparator<T> {
public int compare(T o1, T o2);

public boolean equals(Object obj);
}示例:
·真正有用的只有compare()方法，需要单独建一个类实现Comparator接口。
·使用Comparator接口后用的是Arrays类另一个被重载的sort方法:



import java.util.Arrays;
import java.util.Comparator;

class Book {
private String title;
private double price;

public Book(String title, double price) {
this.title = title;
this.price = price;
}

public String getTitle() {
return title;
}

public void setTitle(String title) {
this.title = title;
}

public double getPrice() {
return price;
}

public void setPrice(double price) {
this.price = price;
}

@Override
public String toString() {
return "书名:《" + this.title + "》价格:" + this.price + "元。";
}
}

class BookComparator implements Comparator<Book> {
@Override
public int compare(Book o1, Book o2) {
if (o1.getPrice() > o2.getPrice()) {
return 1;
} else if (o1.getPrice() < o2.getPrice()) {
return -1;
} else {
return 0;
}
}

}

public class Demo {
public static void main(String[] args) {
Book books[] = new Book[] {
new Book("MySQL", 55.8),
new Book("Androis", 50.7),
new Book("Oracle", 55.7),
new Book("Java", 48.8),
new Book("JSP", 43.7)

};
Arrays.sort(books, new BookComparator());
for (Book book : books) {
System.out.println(book);
}
}
}