Java的TreeSet与TreeMap

TreeSet：

数据元素可以排序且不可重复

对比：Set接口：HashSet，元素必须重写hashcode 和 equals方法。

去重：比较等于 0 即重复。

TreeMap：

确保key可以排序或者提供比较器

元素可以排序  java.lang.Comparable + compareTo   new TreeSet().

 TreeSet实例

public class Worker implements java.lang.Comparable<Worker> {
	//工种
	private String type;
	//工资
	private double salary;
	public Worker() {
		// TODO Auto-generated constructor stub
	}
	
	
	public Worker(String type, double salary) {
		super();
		this.type = type;
		this.salary = salary;
	}


	public String getType() {
		return type;
	}
	public void setType(String type) {
		this.type = type;
	}
	public double getSalary() {
		return salary;
	}
	public void setSalary(double salary) {
		this.salary = salary;
	}

	/**
	 * 按工资升序
	 */
	@Override
	public int compareTo(Worker o) {
		return this.salary>o.salary?1:( this.salary==o.salary?0:-1);
	}
	
	@Override
	public String toString() {
		return "工种:"+this.type+",工资:"+this.salary+"\n";
	}
	
}


import java.util.TreeSet;
/**
 * 实体类实现Comparable 接口的应用
 * @author Administrator
 *
 */
public class TreeSetDemo2 {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		Worker w1 =new Worker("垃圾回收员",12000);
		Worker w2 =new Worker("农民工",8000);
		Worker w3 =new Worker("程序猿",5000);
		
		TreeSet<Worker> employees =new TreeSet<Worker>();
		employees.add(w1);
		employees.add(w2);
		employees.add(w3);
		System.out.println(employees);
		
	}

}

    TreeMap实例

public class Worker implements java.lang.Comparable<Worker> {
	//工种
	private String type;
	//工资
	private double salary;
	public Worker() {
		// TODO Auto-generated constructor stub
	}
	
	
	public Worker(String type, double salary) {
		super();
		this.type = type;
		this.salary = salary;
	}


	public String getType() {
		return type;
	}
	public void setType(String type) {
		this.type = type;
	}
	public double getSalary() {
		return salary;
	}
	public void setSalary(double salary) {
		this.salary = salary;
	}

	/**
	 * 按工资升序
	 */
	@Override
	public int compareTo(Worker o) {
		return this.salary>o.salary?1:( this.salary==o.salary?0:-1);
	}
	
	@Override
	public String toString() {
		return "工种:"+this.type+",工资:"+this.salary+"\n";
	}
	
}

import java.util.TreeMap;

public class TreeMapDemo02 {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		Worker w1 =new Worker("垃圾回收员",12000);
		Worker w2 =new Worker("农民工",8000);
		Worker w3 =new Worker("程序猿",5000);
		
		TreeMap<Worker,String > employees =new TreeMap<Worker,String >();
		employees.put(w1,"bjsxt");
		employees.put(w2,"bjsxt");
		employees.put(w3,"bjsxt");
		System.out.println(employees.keySet());
	}

}

2）排序业务类 java.uti.Comparator + compare        new TreeSet(Comparator <? super E > comparator)

注意：在添加数据时排序，数据更改不会·影响原来的顺序，不要修改数据，否则可能重复 

TreeSet实例

//TreeSet
public class Person {
	private final String name;//名称
	private final int handsome;//帅气指数
	
	public Person() {
		name =null;
		handsome =0;
	}

	public Person(String name, int handsome) {
		super();
		this.name = name;
		this.handsome = handsome;
	}

	public String getName() {
		return name;
	}

	public int getHandsome() {
		return handsome;
	}
	
	@Override
	public String toString() {
		return "姓名:"+this.name+",帅气指数:"+this.handsome+"\n";
	}
}

/**
 * 提供了 解耦的方式:业务排序类
 * @author Administrator
 *
 */
public class TreeSetDemo {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		Person p1 =new Person("您",100);
		Person p2 =new Person("刘德华",1000);
		Person p3 =new Person("梁朝伟",1200);
		Person p4 =new Person("老裴",50);
		
		//依次存放到TreeSet容器中,使用排序的业务类(匿名内部类)
		TreeSet<Person> persons =new TreeSet<Person>(
			new java.util.Comparator<Person>(){

			@Override
		        public int compare(Person o1, Person o2) {
			    return -(o1.getHandsome()-o2.getHandsome());
			}
						
		        }
		);
		persons.add(p1);
		//TreeSet 在添加数据时排序
		persons.add(p2);
		persons.add(p3);
		persons.add(p4);
		
		System.out.println(persons);
		
		/*
		//改变数据
		p4.setHandsome(100);
		p4.setName("您");
		*/ 
		//p4 与p1 内容重复 
		System.out.println(persons);
		
	}

}

//TreeMap
public class Worker implements java.lang.Comparable<Worker> {
	//工种
	private String type;
	//工资
	private double salary;
	public Worker() {
		// TODO Auto-generated constructor stub
	}
	
	
	public Worker(String type, double salary) {
		super();
		this.type = type;
		this.salary = salary;
	}


	public String getType() {
		return type;
	}
	public void setType(String type) {
		this.type = type;
	}
	public double getSalary() {
		return salary;
	}
	public void setSalary(double salary) {
		this.salary = salary;
	}

	/**
	 * 按工资升序
	 */
	@Override
	public int compareTo(Worker o) {
		return this.salary>o.salary?1:( this.salary==o.salary?0:-1);
	}
	
	@Override
	public String toString() {
		return "工种:"+this.type+",工资:"+this.salary+"\n";
	}
	
}




import java.util.Set;
import java.util.TreeMap;

public class TreeMapDemo {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		Person p1 =new Person("您",100);
		Person p2 =new Person("刘德华",1000);
		Person p3 =new Person("梁朝伟",1200);
		Person p4 =new Person("老裴",50);
		
		TreeMap<Person,String> map =new TreeMap<Person,String>(
                    new java.util.Comparator<Person>(){

			@Override
			public int compare(Person o1, Person o2) {
				return -(o1.getHandsome()-o2.getHandsome());
			}
		    } 
                );
		map.put(p1, "bjsxt");
		map.put(p2, "bjsxt");
		map.put(p3, "bjsxt");
		map.put(p4, "bjsxt");
		
		//查看键
		Set<Person> persons =map.keySet();
		System.out.println(persons);
	}

}

TreeSet添加自定义元素:
 TreeSet要注意的事项：
  1. 往TreeSet添加元素的时候，如果元素本身具备了自然顺序的特性，那么就按照元素自然顺序的特性进行排序存储。
  2. 往TreeSet添加元素的时候，如果元素本身不具备自然顺序的特性，那么该元素所属的类必须要实现Comparable接口，把元素的比较规则定义在compareTo(T o)方法上。 
 
  3. 如果比较元素的时候，compareTo方法返回 的是0，那么该元素就被视为重复元素，不允许添加.(注意：TreeSet与HashCode、equals方法是没有任何关系。)
 
  4. 往TreeSet添加元素的时候, 如果元素本身没有具备自然顺序 的特性，而元素所属的类也没有实现Comparable接口，那么必须要在创建TreeSet的时候传入一个比较器。
 
  5.  往TreeSet添加元素的时候，如果元素本身不具备自然顺序的特性，而元素所属的类已经实现了Comparable接口， 在创建TreeSet对象的时候也传入了比较器那么是以比较器的比较规则优先使用。