JAVA比较器：利用Comparable和Comparator进行排序

一：自然排序：Comparable

        实现了comparable的对象直接就可以成为一个可以比较的对象。

        定义一个类实现Comparable接口，并重写compareTo方法，compareTo方法中要指明排序方式

class Person implements Comparable{
    private String name;
    @Override
    public String toString() {
        return "Person{" +
                "name='" + name + '\'' +
                '}';
    }

    public String getName() {
        return name;
    }

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

    public Person(String name) {
        this.name = name;
    }

    @Override
    public int compareTo(Object o) {
        if (o instanceof Person) {
            Person p = (Person) o;
            return this.name.compareTo(p.name);
        }
        throw new RuntimeException("异常");
    }
}

        之后在main方法中进行测试        

public static void main(String[] args) {
        String [] arr = {"史蛋","二度","香肠","倒萨"};
        Arrays.sort(arr);
        System.out.println(Arrays.toString(arr));
    }
}

        输出结果为

二：定制排序：Comparator

       与类中的compareTo方法相似，但这里用到了两个参数。

        “-”号代表逆序，自然排序为顺序

 public static void main(String[] args) {
        String [] arr = {"史蛋","二度","香肠","倒萨"};
//        Arrays.sort(arr);
        Arrays.sort(arr, new Comparator() {
            @Override
            public int compare(String o1, String o2) {
                if (o1 instanceof String && o2 instanceof String) {
                   String s1 = o1;
                   String s2 = o2;
                   return -o1.compareTo(o2);
                }
                throw new RuntimeException("异常");
            }
        });
        System.out.println(Arrays.toString(arr));
    }
}

        输出结果：

 三：练习：自定义泛型及Compare自定义排序，对bag按照价格及品牌名称进行排序

        定义Bags类实现Comparable接口，并重写compareTo方法

class Bages implements Comparable{
    private String name;
    private double price;

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

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

    @Override
    public int compareTo(Object o) {
        if (o instanceof Bages) {
            Bages bages = (Bages) o;
            if (this.price > bages.price) {
                return 1;
            }else if (this.price < bages.price) {
                return -1;
            }else {
                //名字排序，按照字母顺序（-this表示逆序）
                return this.name.compareTo(bages.name);
            }
        }else {
            throw new RuntimeException("异常");
        }
    }
}

        main方法进行测试

 public static void main(String[] args) {
        Bages[] arr = new Bages[4];
        arr[0] = new Bages("loose", 52000);
        arr[1] = new Bages("loosa", 23000);
        arr[2] = new Bages("zippo", 12000);
        arr[3] = new Bages("ziaoop", 2600);
//        自然排序
        Arrays.sort(arr);
        System.out.println(Arrays.toString(arr));
        System.out.println("*********************");
//        定制排序
        Arrays.sort(arr, new Comparator() {
            @Override
            public int compare(Bages o1, Bages o2) {
                if (o1 instanceof Bages && o2 instanceof Bages) {
                    Bages b1 = o1;
                    Bages b2 = o2;
                    if (b1.getName().equals(b2.getName())) {
                        return -Double.compare(b1.getPrice(),b2.getPrice());
                    }else {
                        return Double.compare(b1.getPrice(),b2.getPrice());
                    }
                }
                throw new RuntimeException("异常");
            }
        });
        System.out.println(Arrays.toString(arr));
    }
}

        运行结果