# Java集合之TreeSet

**Repository Path**: fpfgitmy_admin/java-collection-treeset

## Basic Information

- **Project Name**: Java集合之TreeSet
- **Description**: No description available
- **Primary Language**: Unknown
- **License**: Not specified
- **Default Branch**: master
- **Homepage**: None
- **GVP Project**: No

## Statistics

- **Stars**: 1
- **Forks**: 0
- **Created**: 2021-04-28
- **Last Updated**: 2021-04-28

## Categories & Tags

**Categories**: Uncategorized

**Tags**: None

## README

#### TreeSet源码分析
+ treeSet底层用的红黑树
+ 可以按照对象的属性值进行排序
+ 向TreeSet中添加的数据，要求是相同类的对象
+ 两种排序方式：自然排序(实现Comparable接口)和定制排序（Comparator）
+ 自然排序中，比较两个对象是否相同的标准为：compareTo()返回0，不再是equals()
+ 定制排序中，比较两个对象师傅相同的标准为：compare()返回0，不再是equals()

##### 自然排序模拟
1. 创建实现Comparable接口的类并重写compareTo()方法
```
package com.felixfei.study.model;

/**
 * @describle
 */
public class User implements Comparable {

    private String name;
    private int age;

    public User(String name, int age) {
        this.name = name;
        this.age = age;
    }

    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;
    }

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

    // 按照姓名从小到大排序,按照年龄从小到大排序
    @Override
    public int compareTo(Object o) {
        if (o instanceof User) {
            User user = (User) o;
            int compare = this.name.compareTo(user.name);
            if (compare != 0) {
                return compare;
            } else {
                return Integer.compare(this.age, user.age);
            }
        } else {
            throw new RuntimeException("输入类型不匹配");
        }
    }
}

```
2. TreeSet方法的使用
```
package com.felixfei.study.test;

import com.felixfei.study.model.User;

import java.util.Iterator;
import java.util.Set;
import java.util.TreeSet;

/**
 * @describle
 */
public class TestTreeSet {

    public static void main(String[] args) {
        TreeSet set = new TreeSet<>();
        set.add(new User("Tom",12));
        set.add(new User("Jack",11));
        set.add(new User("Mike",22));
        set.add(new User("Jim",23));
        set.add(new User("Jim",56));
        Iterator iterator = set.iterator();
        while (iterator.hasNext()) {
            System.out.println(iterator.next());
        }
    }
}

```

##### 定制排序模拟
1. 编写user类
```
package com.felixfei.study.model;

/**
 * @describle
 */
public class User{

    private String name;
    private int age;

    public User(String name, int age) {
        this.name = name;
        this.age = age;
    }

    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;
    }

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

```
2. 定制排序模拟
```
package com.felixfei.study.test;

import com.felixfei.study.model.User;

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

/**
 * @describle
 */
public class TestTreeSet {

    public static void main(String[] args) {

        // 编写定制排序方法
        Comparator com = new Comparator() {
            // 按照年龄从小到大排列
            @Override
            public int compare(Object o1, Object o2) {
                if (o1 instanceof User && o2 instanceof User) {
                    User u1 = (User) o1;
                    User u2 = (User) o2;
                    return Integer.compare(u1.getAge(), u2.getAge());
                } else {
                    throw new RuntimeException("输入类型不匹配");

                }
            }
        };
        TreeSet set = new TreeSet<>(com);
        set.add(new User("Tom", 12));
        set.add(new User("Jack", 11));
        set.add(new User("Mike", 22));
        set.add(new User("Jim", 23));
        set.add(new User("Jim", 56));
        Iterator iterator = set.iterator();
        while (iterator.hasNext()) {
            System.out.println(iterator.next());
        }
    }
}

```