Java Comparable与Comparator

THRFUR

#Comparable case

import java.util.Arrays;

public class ComparableTest {
    public static void main(String[] args) {
        Goods[] goods = new Goods[]{
                new Goods("Phone", 5000),
                new Goods("TV", 3500),
                new Goods("Computer", 10000)
        };
        Arrays.sort(goods);
        System.out.println(Arrays.toString(goods));
    }
}

class Goods implements Comparable {
    private final String goodsName;
    private final int goodsPrice;

    public Goods(String goodsName, int goodsPrice) {
        this.goodsName = goodsName;
        this.goodsPrice = goodsPrice;
    }

    @Override
    public String toString() {
        return "goodsName:" + goodsName + "，goodsPrice:" + goodsPrice + "\n";
    }

    /**
     * 如果当前对象this大于形参对象obj，则返回正整数
     * 如果当前对象this小于形参对象obj，则返回负整数
     * 如果当前对象this等于形参对象obj，则返回零
     * @param o 传入的待排序类
     * @return 比较值
     */

    @Override
    public int compareTo(Object o) {
        if (o instanceof Goods) {
            Goods goods = (Goods) o; //首先需要强转类型
            /*
             * 价格比较方式一
             * if (this.goodsPrice > goods.goodsPrice) {
             *     return 1;
             * } else if (this.goodsPrice < goods.goodsPrice) {
             *     return -1;
             * } else return 0;
             */

            /*
             * 价格比较方式二，调用xxx.compare()方法
             */
            return Integer.compare(this.goodsPrice, goods.goodsPrice);


            /*
             * 商品名称比较，因为String类型重写了compareTo方法，所以可以直接调用compareTo方法
             * return this.goodsName.compareTo(goods.goodsName);
            */

        } else throw new RuntimeException("传入的类型不一致");
    }
}

运行结果：

[goodsName:TV，goodsPrice:3500
, goodsName:Phone，goodsPrice:5000
, goodsName:Computer，goodsPrice:10000
]

#Comparator case

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

public class ComparatorTest {
    public static void main(String[] args) {
        Books[] books = new Books[] {
                new Books("Core Java", 200),
                new Books("Effective Java", 189),
                new Books("Effective Java", 179),
                new Books("Mysql", 210)
        };

        //new一个Comparator匿名对象，泛型参数为Books类
        Arrays.sort(books, new Comparator<Books>() {
            @Override
            public int compare(Books o1, Books o2) {
                if (o1 instanceof Books && o2 instanceof Books) {
                    Books b1 = (Books) o1;
                    Books b2 = (Books) o2;
                    if (b1.getBookName().equals(b2.getBookName())) {
                        return Integer.compare(b1.getBookPrice(), b2.getBookPrice());
                    } else return b1.getBookName().compareTo(b2.getBookName());
                } else throw new RuntimeException("传入的类型不一致");
            }
        });

        System.out.println(Arrays.toString(books));
    }
}
class Books{
    private String bookName;
    private int bookPrice;

    public Books(String bookName, int bookPrice) {
        this.bookName = bookName;
        this.bookPrice = bookPrice;
    }

    public String getBookName() {
        return bookName;
    }

    public int getBookPrice() {
        return bookPrice;
    }

    @Override
    public String toString() {
        return "Books{" +
                "bookName='" + bookName + '\'' +
                ", bookPrice=" + bookPrice +
                "}\n";
    }
}

运行结果：

[Books{bookName='Core Java', bookPrice=200}
, Books{bookName='Effective Java', bookPrice=179}
, Books{bookName='Effective Java', bookPrice=189}
, Books{bookName='Mysql', bookPrice=210}
]