Java排序方法--List，数组，【自定义】继承Comparable和Comparator

（一）list和数组

①List默认排序代码：

public static void main(String[] args) {
    List<String> list = new ArrayList<>();
    list.add("阿a里 ");
    list.add("不b安定 ");
    list.add("嘻x嘻 ");
    list.add("一y一 ");
    list.add("传c递 ");
    list.add("东d西 ");
    list.add("耳e朵 ");
    list.add("分f数 ");

    for (int i=0;i<list.size();i++){
        System.out.print(list.get(i));
    }

    //降序【以现有list的顺序----从后往前输出 】
    System.out.println(" 降序");

    Collections.reverse(list);
    for (int i=0;i<list.size();i++){
        System.out.print(list.get(i));
    }
    //依照list 现在顺序---从前往后读  一y一 不b安定 东d西 传c递 分f数 嘻x嘻 耳e朵 阿a里
    System.out.println(" 升序");
    Collections.sort(list);
    for (int i=0;i<list.size();i++){
        System.out.print(list.get(i));
    }
    System.out.println("按照汉语拼音排序");
    //排序  abcdefg这么来的【首字母按照汉语拼音来的】
    Collections.sort(list,Collator.getInstance(Locale.CHINA));
    for (int i=0;i<list.size();i++){
        System.out.print(list.get(i));
    }

}

②：数组：

String[] names = {"阿a里", "把b把", "阿a里", "得d到", "额e额", "得d到","阿b里"};
//应该是根据ASCII码这么来的
Arrays.sort(names);
System.out.println(Arrays.toString(names));
Arrays.sort(names,Collator.getInstance(Locale.CHINA));
//根据中文字母表排序，先比较第一个字母拼音，再比较第二个字母拼音。

System.out.println(Arrays.toString(names));

（二）自定义排序：

①实现Comparable接口，类内设比较项。

public class Test1 implements Comparable {
    /*
   * 1.实现Comparable接口
   * 重写int compareTo（Object o）方法
   * */
    private String name;
    private Integer age;

    public String getName() {
        return name;
    }

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

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    public Test1(String name, Integer age) {
        this.name = name;
        this.age = age;
    }

    @Override
    public int compareTo(Object o) {
        Test1 sutdent = (Test1) o;
        int age1 = sutdent.getAge();
        return this.age.compareTo(age1);
    }

    public static void main(String[] args) {
        List<Test1> students = new ArrayList<>();
        Test1 s1 = new Test1("十一", 11);
        Test1 s2 = new Test1("十二", 12);
        Test1 s3 = new Test1("十三", 13);
        Test1 s4 = new Test1("十四", 14);
        students.add(s1);
        students.add(s4);
        students.add(s2);
        students.add(s3);
        students.add(s2);
        //reverse 仅仅只是反转
        Collections.reverse(students);
        for (Test1 t : students) {
            System.out.print(t.getAge() + "  ");
        }

        //调用自己的类的int属性进行比较
        Collections.sort(students);

        for (Test1 t : students) {
            System.out.print(t.getAge() + "  ");
        }
        System.out.println("   ");

    }

}

②实现Comparator接口，类外设比较项。

public class Test1 implements Comparator<Test1> {
    /*
   * 1.实现Comparable接口
   * 重写int compareTo（Object o）方法
   * */
    private String name;
    private Integer age;

    public String getName() {
        return name;
    }

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

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    public Test1() {
    }

    public Test1(String name, Integer age) {
        this.name = name;
        this.age = age;
    }
    @Override
    public int compare(Test1 o1, Test1 o2) {
        return o1.age.compareTo(o2.age);
    }

    public static void main(String[] args) {
        Test1 s1=new Test1("小1",11);
        Test1 s3=new Test1("小3",13);
        Test1 s2=new Test1("小2",12);
        Test1 s4=new Test1("小4",14);
        //Array.adList就是固定长度集合。
        List<Test1> students=Arrays.asList(s1,s3,s2,s4);
        for (Test1 s:students){
            System.out.print(s.age+" ");
        }
        System.out.println("排序后");
        Collections.sort(students,new Test1());
        for (Test1 s:students){
            System.out.print(s.age+"  ");
        }

      }
    }