Java中的TreeSet集合解析

    TreeSet(NavigableMap<E,Object> m) {
        this.m = m;
    }

    public TreeSet() {
        this(new TreeMap<E,Object>());
    }

    public TreeSet(Comparator<? super E> comparator) {
        this(new TreeMap<>(comparator));
    }

    public TreeSet(Collection<? extends E> c) {
        this();
        addAll(c);
    }

    public TreeSet(SortedSet<E> s) {
        this(s.comparator());
        addAll(s);
    }

//遍历方法，返回m.keyset集合
    public Iterator<E> iterator() {
        return m.navigableKeySet().iterator();
    }
    //逆序排序的迭代器
    public Iterator<E> descendingIterator() {
        return m.descendingKeySet().iterator();
    }
    /**
     * @since 1.6
     */
    public NavigableSet<E> descendingSet() {
        return new TreeSet<>(m.descendingMap());
    }
    //返回 m 包含的键值对的数量
    public int size() {
        return m.size();
    }
    //是否为空
    public boolean isEmpty() {
        return m.isEmpty();
    }
    //是否包含指定的key
    public boolean contains(Object o) {
        return m.containsKey(o);
    }
    //添加元素，调用m.put方法实现
    public boolean add(E e) {
        return m.put(e, PRESENT)==null;
    }
    //删除方法，调用m.remove()方法实现
    public boolean remove(Object o) {
        return m.remove(o)==PRESENT;
    }
    //清除集合
    public void clear() {
        m.clear();
    }
    //将一个集合中的所有元素添加到TreeSet中
    public  boolean addAll(Collection<? extends E> c) {
        // Use linear-time version if applicable
        if (m.size()==0 && c.size() > 0 &&
            c instanceof SortedSet &&
            m instanceof TreeMap) {
            SortedSet<? extends E> set = (SortedSet<? extends E>) c;
            TreeMap<E,Object> map = (TreeMap<E, Object>) m;
            Comparator<? super E> cc = (Comparator<? super E>) set.comparator();
            Comparator<? super E> mc = map.comparator();
            if (cc==mc || (cc != null && cc.equals(mc))) {
                map.addAllForTreeSet(set, PRESENT);
                return true;
            }
        }
        return super.addAll(c);
    }
    //返回子集合，通过 m.subMap()方法实现
    public NavigableSet<E> subSet(E fromElement, boolean fromInclusive,
                                  E toElement,   boolean toInclusive) {
        return new TreeSet<>(m.subMap(fromElement, fromInclusive,
                                       toElement,   toInclusive));
    }
    //返回set的头部
    public NavigableSet<E> headSet(E toElement, boolean inclusive) {
        return new TreeSet<>(m.headMap(toElement, inclusive));
    }
    //返回尾部
    public NavigableSet<E> tailSet(E fromElement, boolean inclusive) {
        return new TreeSet<>(m.tailMap(fromElement, inclusive));
    }
    //返回子Set
    public SortedSet<E> subSet(E fromElement, E toElement) {
        return subSet(fromElement, true, toElement, false);
    }
    //返回set的头部
    public SortedSet<E> headSet(E toElement) {
        return headSet(toElement, false);
    }
    //返回set的尾部
    public SortedSet<E> tailSet(E fromElement) {
        return tailSet(fromElement, true);
    }
    //返回m使用的比较器
    public Comparator<? super E> comparator() {
        return m.comparator();
    }
    //返回第一个元素
    public E first() {
        return m.firstKey();
    }
    //返回最后一个元素
    public E last() {
        return m.lastKey();
    }
    //返回set中小于e的最大的元素
    public E lower(E e) {
        return m.lowerKey(e);
    }
    //返回set中小于/等于e的最大元素
    public E floor(E e) {
        return m.floorKey(e);
    }
    //返回set中大于/等于e的最大元素
    public E ceiling(E e) {
        return m.ceilingKey(e);
    }
    //返回set中大于e的最小元素
    public E higher(E e) {
        return m.higherKey(e);
    }
    //获取TreeSet中第一个元素，并从Set中删除该元素
    public E pollFirst() {
        Map.Entry<E,?> e = m.pollFirstEntry();
        return (e == null) ? null : e.getKey();
    }
    //获取TreeSet中最后一个元素，并从Set中删除该元素
    public E pollLast() {
        Map.Entry<E,?> e = m.pollLastEntry();
        return (e == null) ? null : e.getKey();
    }
    //克隆方法
    public Object clone() {
        TreeSet<E> clone = null;
        try {
            clone = (TreeSet<E>) super.clone();
        } catch (CloneNotSupportedException e) {
            throw new InternalError();
        }
        clone.m = new TreeMap<>(m);
        return clone;
    }
    //将对象写入到输出流中。
    private void writeObject(java.io.ObjectOutputStream s)
        throws java.io.IOException {
        // Write out any hidden stuff
        s.defaultWriteObject();
        // Write out Comparator
        s.writeObject(m.comparator());
        // Write out size
        s.writeInt(m.size());
        // Write out all elements in the proper order.
        for (E e : m.keySet())
            s.writeObject(e);
    }
    //从输入流中读取对象的信息
    private void readObject(java.io.ObjectInputStream s)
        throws java.io.IOException, ClassNotFoundException {
        // Read in any hidden stuff
        s.defaultReadObject();
        // Read in Comparator
        Comparator<? super E> c = (Comparator<? super E>) s.readObject();
        // Create backing TreeMap
        TreeMap<E,Object> tm;
        if (c==null)
            tm = new TreeMap<>();
        else
            tm = new TreeMap<>(c);
        m = tm;
        // Read in size
        int size = s.readInt();
        tm.readTreeSet(size, s, PRESENT);
    }

 
import java.util.*;
class Student{
    private int id;
    private String name;
    private int age;
    public Student(int id, String name, int age) {
        this.id = id;
        this.name = name;
        this.age = age;
    }
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    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 "Student{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", age=" + age +
                '}';
    }
}
class MyComparator implements Comparator{
    @Override
    public int compare(Object o1, Object o2) {
        Student s1 = (Student) o1;
        Student s2 = (Student) o2;
        return s1.getAge() - s2.getAge();
    }
}
public class Main {
    public static void main(String[] args) {
        TreeSet treeSet = new TreeSet(new MyComparator());
        treeSet.add(new Student(1, "tom", 23));
        treeSet.add(new Student(2, "Jerry", 20));
        treeSet.add(new Student(3, "Jack", 17));
        treeSet.add(new Student(4, "Marry", 54));
        treeSet.add(new Student(5, "Baby", 8));
        Iterator iterator = treeSet.iterator();
        while(iterator.hasNext()){
            System.out.println(iterator.next());
        }
    }
}

import java.util.*;
class Student implements Comparable{
    private int id;
    private String name;
    private int age;
    public Student(int id, String name, int age) {
        this.id = id;
        this.name = name;
        this.age = age;
    }
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    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 "Student{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", age=" + age +
                '}';
    }
    @Override
    public int compareTo(Object o) {
        if(!(o instanceof Student)){
            throw new RuntimeException("对象有问题");
        }
        Student s = (Student) o;
        if(this.age > s.age){
            return -1;
        }else{
            return 1;
        }
    }
}
public class Main {
    public static void main(String[] args) {
        TreeSet treeSet = new TreeSet();
        treeSet.add(new Student(1, "tom", 23));
        treeSet.add(new Student(2, "Jerry", 20));
        treeSet.add(new Student(3, "Jack", 17));
        treeSet.add(new Student(4, "Marry", 54));
        treeSet.add(new Student(5, "Baby", 8));
        Iterator iterator = treeSet.iterator();
        while(iterator.hasNext()){
            System.out.println(iterator.next());
        }
    }
}