java中api的各种排序(更新中,欢迎大佬指点)

 

1. 基本数组:

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

 

2.对象数组:

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//通过实现Comparable接口来排序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)//实现Comparator接口来排序 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) -> {             //这里比较的可以是多个 ,name长度比较, name直接自然顺序比较,代码显示的是成绩比较和年级比较             int num = o2.score-o1.score;//成绩降序             int num1 = num == 0?o1.age-o2.age:num;//  若果成绩相等的话就判断年龄  年龄升序  ;             return num1;           });           for (student student : arr) {             System.out.println(student);         }

 结果显示:

　　

3.list排序

//简单的Integer类型
//直接用 Colletions工具类
ArrayList<Integer>  list =  new ArrayList<>();
        list.add(9);
        list.add(3);
        list.add(5);
        list.add(1);
        Collections.sort(list);
        System.out.println(list);

        结果:[1, 3, 5, 9]

 

//list存储学生对象排序
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) ->{
            //这里比较的可以是多个 ,name长度比较, name直接自然顺序比较,代码显示的是成绩比较和年级比较
            int num = o2.score-o1.score;//成绩降序
            int num1 = num == 0?o1.age-o2.age:num;//  若果成绩相等的话就判断年龄  年龄升序  ;
            return num1;
            }
        );
        System.out.println(list);
    }
    //结果[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

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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它存储无序,离散,所以无法直接排序,只能间接排序了. 介绍两种办法 ,1转成List进行排序 2转成TreeSet进行排序         //list前面已经排序过,这里就不展示了,这里就展示转换成ThreeSet再排序,看代码;         HashSet<student> hashSet = new HashSet<>();         hashSet.add( new student("貂蝉",42,100));         hashSet.add( new student("后裔",43,100));         hashSet.add( new student("孙悟空",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直接操作一个类,这里就不演示了, 直接上Comparator操作对象这个简便的             //这里比较的可以是多个 ,name长度比较, name直接自然顺序比较,代码显示的是成绩比较和年级比较             int num = o2.score-o1.score;//成绩降序             int num1 = num == 0?o1.age-o2.age:num;//  若果成绩相等的话就判断年龄  年龄升序  ;             return num1;         });           //交换元素         for (student student : hashSet) {             set.add(student);         }         System.out.println(set);         //结果[student{name='貂蝉',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='孙悟空', age=4, score=35}]         }

　　

5.map排序 看这里  能力有限 写不下去了 学的越多 你会发现 你知道的越少 调整心态才是重要的