java中api的各種排序(更新中,歡迎大佬指點)

 

1. 基本數組:

         //直接通過Arrays.sort工具類
          int[] arr = new int[]{1,2,6,24,5,68,9,0};
          Arrays.sort(arr);

 

2.對象數組:

//通過實現Comparable接口來排序

public class student implements Comparable<student> {
    String name;
    int age;
    public student(String name, int age) {
        this.name = name;
        this.age = age;
    }

    @Override
    public int compareTo(student o) {
//        return this.age-o.age;//升序
        return o.age- this.age;//降序
    }
}

       student[] arr = new student[]{ new student("a",4), new student("a",7),new student("a",1)};
        Arrays.sort(arr)

//實現Comparator接口來排序
public class student {
    String name;
    int age;
    int score;
    public student(String name, int age, int score) {
        this.name = name;
        this.age = age;
        this.score = score;
    }

    @Override
    public String toString() {
        return "student{" +
                "name='" + name + '\'' +
                ", age=" + age +
                ", score=" + score +
                '}';
    }
}
   student[] arr = new student[]{
                new student("a",4,100),
                new student("b",9,100),
                new student("c",7,80),
                new student("d",20,100),
                new student("f",11,50),

        };

        Arrays.sort(arr,(o1, o2) -> {
            //這里比較的可以是多個 ,name長度比較, name直接自然順序比較,代碼顯示的是成績比較和年級比較
            int num = o2.score-o1.score;//成績降序
            int num1 = num == 0?o1.age-o2.age:num;//  若果成績相等的話就判斷年齡  年齡升序  ;
            return num1;

        });

        for (student student : arr) {
            System.out.println(student);
        }

 結果顯示:

　　

3.list排序

//簡單的Integer類型
//直接用 Colletions工具類
ArrayList<Integer>  list =  new ArrayList<>();
        list.add(9);
        list.add(3);
        list.add(5);
        list.add(1);
        Collections.sort(list);
        System.out.println(list);

        結果:[1, 3, 5, 9]

 

//list存儲學生對象排序
public class student {
    String name;
    int age;
    int score;
    public student(String name, int age, int score) {
        this.name = name;
        this.age = age;
        this.score = score;
    }

    @Override
    public String toString() {
        return "student{" +
                "name='" + name + '\'' +
                ", age=" + age +
                ", score=" + score +
                '}';
    }
}
  ArrayList<student>  list =  new ArrayList<>();
        list.add( new student("a",4,100));
        list.add(new student("b",9,100));
        list.add(new student("d",20,100));
        list.add(new student("c",7,80));
        list.add(new student("f",11,50));
        Collections.sort(list,(o1, o2) ->{
            //這里比較的可以是多個 ,name長度比較, name直接自然順序比較,代碼顯示的是成績比較和年級比較
            int num = o2.score-o1.score;//成績降序
            int num1 = num == 0?o1.age-o2.age:num;//  若果成績相等的話就判斷年齡  年齡升序  ;
            return num1;
            }
        );
        System.out.println(list);
    }
    //結果[student{name='a', age=4, score=100},
    // student{name='b', age=9, score=100},
    // student{name='d', age=20, score=100},
    // student{name='c', age=7, score=80},
    // student{name='f', age=11, score=50}]

4.set排序

public class student implements Comparable<student> {
    String name;
    int age;
    int score;
    public student(String name, int age, int score) {
        this.name = name;
        this.age = age;
        this.score = score;
    }

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

    @Override
    public int compareTo(student o) {
        return this.score-o.score;//score升序
    }
}
/HashSet它存儲無序,離散,所以無法直接排序,只能間接排序了. 介紹兩種辦法 ,1轉成List進行排序 2轉成TreeSet進行排序
        //list前面已經排序過,這里就不展示了,這里就展示轉換成ThreeSet再排序,看代碼;
        HashSet<student> hashSet = new HashSet<>();
        hashSet.add( new student("貂蟬",42,100));
        hashSet.add( new student("后裔",43,100));
        hashSet.add( new student("孫悟空",4,35));
        hashSet.add( new student("阿珂",7,58));
        hashSet.add( new student("妲己",22,80));
        TreeSet<student> set = new TreeSet<>((o1, o2) ->
        {
            //排序用Comparable或者Comparator Comparable直接操作一個類,這里就不演示了, 直接上Comparator操作對象這個簡便的
            //這里比較的可以是多個 ,name長度比較, name直接自然順序比較,代碼顯示的是成績比較和年級比較
            int num = o2.score-o1.score;//成績降序
            int num1 = num == 0?o1.age-o2.age:num;//  若果成績相等的話就判斷年齡  年齡升序  ;
            return num1;
        });

        //交換元素
        for (student student : hashSet) {
            set.add(student);
        }
        System.out.println(set);
        //結果[student{name='貂蟬',age=42, score=100},
        // student{name='后裔', age=43, score=100},
        // student{name='妲己', age=22, score=80},
        // student{name='阿珂', age=7, score=58},
        // student{name='孫悟空', age=4, score=35}]


    }

　　

5.map排序 看這里  能力有限 寫不下去了 學的越多 你會發現 你知道的越少 調整心態才是重要的