一，比較器

比較變量之間的大小 -> 排序

1. 可比性

此接口對(duì)實(shí)現(xiàn)它的每個(gè)類(lèi)的對(duì)象強(qiáng)制執(zhí)行排序。

實(shí)現(xiàn)此接口的對(duì)象的數(shù)組, 可以通過(guò)Arrays.sort自動(dòng)排序。

comparable中有個(gè)compareTo方法

將此對(duì)象與指定對(duì)象進(jìn)行順序比較。 當(dāng)此對(duì)象小于、等于或大于指定對(duì)象時(shí)，返回負(fù)整數(shù)、零或正整數(shù)。

2. 比較器

一個(gè)比較接口，它對(duì)某些對(duì)象集合進(jìn)行排序。

可以將比較器(new了一個(gè)實(shí)現(xiàn)了comparator接口的對(duì)象)傳遞給排序方法(例如Collections.sort或Arrays.sort)。

用法場(chǎng)景:

如果這個(gè)類(lèi)是我們自己寫(xiě)的,需要比較排序, 實(shí)現(xiàn)Comprable, 如果不是我們自己寫(xiě)的代碼, 我們無(wú)法修改的代碼, 通過(guò)comparator。

二，Comparable

public class Student implements Comparable<Student>{

    public String name;
    public Integer score;
    public Integer age;

    public Student(String name, Integer score, Integer age) {
        this.name = name;
        this.score = score;
        this.age = age;
    }

    @Override
    public String toString() {
        return "Student{" +
                "name='" + name + '\\'' +
                ", score=" + score +
                ", age=" + age +
                '}';
    }

    /**
     * int aInt = gaoPeng.compareTo(tuEnXia);
     * 此對(duì)象指的是gaoPeng, 指定對(duì)象指的是tuEnXia
     * 將此對(duì)象與指定對(duì)象進(jìn)行大小比較。當(dāng)此對(duì)象小于、等于或大于指定對(duì)象時(shí)，返回負(fù)整數(shù)、零或正整數(shù)
     * @return
     */
    @Override
    public int compareTo(Student other) {
        int diff = this.score - other.score;
        return diff;
    }
}

public class ComparableDemo01 {
    public static void main(String[] args) {
        Student student1 = new Student("張三", 700, 19);
        Student student2 = new Student("李四", 666, 18);
        Student student3 = new Student("王麻子", 750, 19);
//        //1. 數(shù)組排序
//        Student[] students = {student1,student2,student3};
//        Arrays.sort(students);
//        System.out.println(Arrays.toString(students));

        //2, 集合的comparable排序
        ArrayList students = new ArrayList<>();
        students.add(student1);
        students.add(student2);
        students.add(student3);
//        Collections.sort(students);
//        System.out.println(students);
//這個(gè)地方要求傳入一個(gè)Compartor, 如果傳入是個(gè)null, arraylist將會(huì)自動(dòng)調(diào)用本集合中對(duì)象的comparable方法
        students.sort(null);
        System.out.println(students);
    }
}

三，Comparator

public class PointComparator implements Comparator<Point> {

    @Override
    public int compare(Point point1, Point point2) {
        int diff = point1.x + point1.y - point2.x - point2.y;
        return diff;
    }
}

public class PointComparator {
    public static  void main(String[] args) {
        Point point1 = new Point(44, 55);
        Point point2 = new Point(58, 56);
        Point point3 = new Point(58, 96);
        //1,數(shù)組排序
//        Point[] points = {point1,point2,point3};
//        Arrays.sort(points,new PointComparator());
//        System.out.println(Arrays.toString(points));
        //2 集合排序
        LinkedList<Point> linkedList = new LinkedList<>();
        linkedList.add(point1);
        linkedList.add(point2);
        linkedList.add(point3);
//        Collections.sort(linkedList,new PointComparator());
//       linkedList.sort(new PointComparator());
//        System.out.println(linkedList);
        //3 通過(guò)匿名內(nèi)部類(lèi)排序
        Comparator<Point> comparator = new Comparator<Point>() {
            @Override
            public int compare(Point o1, Point o2) {
                int diff = o1.x + o1.y - o2.x - o2.y;
                return diff;
            }
        };
//        linkedList.sort(comparator);
        Collections.sort(linkedList,comparator);
        System.out.println(linkedList);
    }
}