TreeSet集合排序方式一：自然排序Comparable

﹏ヽ暗。殇╰゛Y 2022-06-17 04:36 218阅读 0赞

**TreeSet集合默认会进行排序。因此必须有排序，如果没有就会报类型转换异常。**

# **自然排序** #

Person class—>实现Comparable，实现compareTo（）方法

package Homework1and2;
    
    import java.text.CollationKey;
    import java.text.Collator;
    
    /**
     * Person类 有属性  name,age,sex 
       排序规则: 第一条件  年龄降序,第二条件  姓名 降序,第三条件 性别升序
     * @author Administrator
     *
     */
    public class Person implements Comparable<Person> {
        private static String name;
        private int age;
        private String sex;
        public String getName() {
            return name;
        }
        public void setName(String name) {
            this.name = name;
        }
        public int getAge() {
            return age;
        }
        public void setAge(int age) {
            this.age = age;
        }
        public String getSex() {
            return sex;
        }
        public void setSex(String sex) {
            this.sex = sex;
        }
        @Override
        public String toString() {
            return "Person [name=" + name + ", age=" + age + ", sex=" + sex + "]";
        }
        public Person(String name, int age, String sex) {
            super();
            this.name = name;
            this.age = age;
            this.sex = sex;
        }
        public Person() {
            super();
        }
        //排序规则: 第一条件  年龄降序,第二条件  姓名 降序,第三条件 性别升序
        @Override
        public int compareTo(Person o) {
            if(age>o.age){
                return -1;
            }else if(age<o.age){
                return 1;
            }else {
                CollationKey key1=Collator.getInstance().getCollationKey(name);
                CollationKey key2=Collator.getInstance().getCollationKey(o.name);
                int num=key1.compareTo(key2);
                if(num>0){
                    return -1;
                }else if(num<0){
                    return 1;
                }else {
                    CollationKey key3=Collator.getInstance().getCollationKey(sex);
                    CollationKey key4=Collator.getInstance().getCollationKey(o.sex);
                    int s=key3.compareTo(key4);
                    if(s>0){
                        return 1;
                    }else if(s<0){
                        return -1;
                    }else {
                        return 0;
                    }
                }
    
            }
    
        }
    
    }

测试

public class Test1 {
        
        public static void main(String[] args){
            TreeSet<Person> list=new TreeSet<>();
            //年龄降序
            list.add(new Person("李白1", 15, "男"));
            list.add(new Person("李白2", 18, "男"));
            //姓名降序
            list.add(new Person("a妲己3", 20, "女"));
            list.add(new Person("z褒姒4", 20, "女"));
            //性别升序
            list.add(new Person("妲己", 17, "a女"));
            list.add(new Person("妲己", 17, "z男"));
            System.out.println(list);
    
    
        }
    }