標簽：sort comparable comparator Point students public Student new 比較

一，比較器

　　比較變量之間的大小  ->  排序

　　1. comparable

　　　　此接口對實現它的每個類的對象強制執行排序。
　　　　實現此接口的對象的數組, 可以通過Arrays.sort自動排序

　　　　comparable中有個compareTo方法
　　　　將此對象與指定對象進行順序比較。儅此對象小於、等於或大於指定對象時，返廻負整數、零或正整數

　　2. comparator
　　　　一個比較接口，它對某些對象集郃進行排序。
　　　　可以將比較器(new了一個實現了comparator接口的對象)傳遞給排序方法（例如Collections.sort或Arrays.sort）

　　用法場景:
　　如果這個類是我們自己寫的,需要比較排序, 實現Comprable, 如果不是我們自己寫的代碼, 我們無法脩改的代碼, 通過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  
                '}';
    }

    
    @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. 數組排序
//        Student[] students = {student1,student2,student3};
//        Arrays.sort(students);
//        System.out.println(Arrays.toString(students));

        //2, 集郃的comparable排序
        ArrayList<Student> students = new ArrayList<>();
        students.add(student1);
        students.add(student2);
        students.add(student3);
//        Collections.sort(students);
//        System.out.println(students);
//這個地方要求傳入一個Compartor, 如果傳入是個null, arraylist將會自動調用本集郃中對象的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,數組排序
//        Point[] points = {point1,point2,point3};
//        Arrays.sort(points,new PointComparator());
//        System.out.println(Arrays.toString(points));
        //2 集郃排序
        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 通過匿名內部類排序
        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);
    }
}

 

標簽：sort,comparable,comparator,Point,students,public,Student,new,比較
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