Day 15 (java比较器)

    //String、包装类实现了Compare接口，重写了compareTo()方法，给出了比较两个对象大小的方法（默认从低到高）
    @Test
    public void test() {
        String[] str = new String[]{"ab", "ba", "cc", "df", "em", "ee"};
        Arrays.sort(str);
        System.out.println(Arrays.toString(str));
    }
}

public class CompareTest {
    //自定义类实现Compare排序
    @Test
    public void test1() {
        Goods[] goods = new Goods[4]; //创建对象数组
        goods[0] = new Goods("dellMouse", 100);
        goods[1] = new Goods("lianxiangMouse", 200);
        goods[2] = new Goods("xiaomiMouse", 50);
        goods[3] = new Goods("huaweiMouse", 400);
        Arrays.sort(goods); //实现接口并重写了方法后可以进行排序
        System.out.println(Arrays.toString(goods));  //[Goods{name='xiaomiMouse', price=50.0}, Goods{name='dellMouse', price=100.0}, Goods{name='lianxiangMouse', price=200.0}, Goods{name='huaweiMouse', price=400.0}]
    }
}


//自定义类实现Compare排序  需要实现Comparable接口并且重写compareTo()方法
class Goods implements Comparable {
    private String name;
    private double price;

    public Goods() {
    }

    public Goods(String name, double price) {
        this.name = name;
        this.price = price;
    }

    @Override
    public String toString() {
        return "Goods{" +
                "name='" + name + ''' +
                ", price=" + price +
                '}';
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public double getPrice() {
        return price;
    }

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

    //自定义排序的方式：按照price从低到高排序
    @Override
    public int compareTo(Object o) {
        if (o instanceof Goods) {
            Goods goods = (Goods) o; //向上强转
            if (this.price > goods.price) {
                return 1;
            } else if (goods.price > this.price) {
                return -1;
            } else {
                return 0;
            }
        }
        throw new RuntimeException("传入数据类型不匹配！");
    }
}

Comparator接口实现自定义排序： 

    @Test
    public void test(){
        String[] arr = new String[]{"ab","bh","kl","ff","rr","ff"};

        Arrays.sort(arr, new Comparator(){   //调用Comparator构造器并且重写Compare方法
            @Override
            public int compare(Object o1, Object o2) {
                if (o1 instanceof String && o2 instanceof String){
                    String s1 = (String) o1;
                    String s2 = (String) o2;
                    return -s1.compareTo(s2);   //实现从高到低排序
                }
                throw new RuntimeException("传入数据类型不匹配!");
            }
        });
        System.out.println(Arrays.toString(arr));
    }