重学java 58.红黑树相关集合

现在还来得及

                       —— 24.6.3

一、TreeSet

1.概述:

        Treeset是set的实现类

2.特点:

        a.对元素进行排序
        b.无索引
        c.不能存null
        d.线程不安全
        e.元素唯一

3.数据结构:

        红黑树

4.构造

        Treeset() —> 构造一个新的空 set，该 set 根据其元素的自然顺序进行排序 -> ASCII
        Treeset(comparator<? super E> comparator) —> 构造一个新的空 Treeset，它根据指定比较器进行排序

public class Person {
    private String name;
    private Integer age;

    public Person() {
    }

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

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

import java.util.TreeSet;

public class Demo252TreeSet01 {
    public static void main(String[] args) {
        TreeSet<String> set1 = new TreeSet<>();
        set1.add("c.白毛浮绿水");
        set1.add("a.鹅鹅鹅");
        set1.add("b.曲项向天歌");
        set1.add("d.红掌拨清波");
        System.out.println(set1);   // [a.鹅鹅鹅, b.曲项向天歌, c.白毛浮绿水, d.红掌拨清波]
    }
}

import java.util.Comparator;
import java.util.TreeSet;

public class Demo253TreeSet02 {
    public static void main(String[] args) {
        TreeSet<Person> treeSet = new TreeSet<>(new Comparator<Person>() {

            @Override
            public int compare(Person o1, Person o2) {
                return o1.getAge()-o2.getAge();
            }
        });
        treeSet.add(new Person("小明",17));
        treeSet.add(new Person("小红",18));
        treeSet.add(new Person("小刚",16));
        System.out.println(treeSet);    // [Person{name='小刚', age=16}, Person{name='小明', age=17}, Person{name='小红', age=18}]
    }
}

二、TreeMap

1.概述:

        Treeset是set的实现类

2.特点:

        a.对元素进行排序
        b.无索引
        c.key唯一
        d.线程不安全
        e.不能存null

3.数据结构:

        红黑树

4.构造:

        TreeMap() —> 使用键的自然顺序构造一个新的、空的树映射 —> ASCII
        TreeMap(Comparator<?super E> comparator) —> 构造一个新的、空的树映射，该映射根据给定比较器进行排序

import java.util.Comparator;
import java.util.TreeMap;

public class Demo254TreeMap01 {
    public static void main(String[] args) {
        TreeMap<String, String> map = new TreeMap<>();
        map.put("a", "苦难是生活的花开");
        map.put("c","一切都会好的");
        map.put("b","我一直相信");
        System.out.println(map);

        TreeMap<Person, String> map2 = new TreeMap<>(new Comparator<Person>() {
            @Override
            public int compare(Person o1, Person o2) {
                return o1.getAge()-o2.getAge();
            }
        });

        map2.put(new Person("小明",17),"北京");
        map2.put(new Person("小红",18),"上海");
        map2.put(new Person("小刚",16),"江苏");
        System.out.println(map2);
    }
}