集合框架-TreeMap集合

(6)TreeMap集合的練習       

A:TreeMap<String,String>

package cn.itcast_04;

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

/*
 * TreeMap:是基於紅黑樹的Map介面的實現。
 * 
 * HashMap<String,String>
 * 鍵：String
 * 值：String
 */
public class TreeMapDemo {
	public static void main(String[] args) {
		// 建立集合物件，無參，是自然排序
		TreeMap<String, String> tm = new TreeMap<String, String>();

		// 建立元素並新增元素
		tm.put("hello", "你好");
		tm.put("world", "世界");
		tm.put("java", "爪哇");
		tm.put("world", "世界2");
		tm.put("javaee", "爪哇EE");

		// 遍歷集合
		Set<String> set = tm.keySet();
		for (String key : set) {
			String value = tm.get(key);
			System.out.println(key + "---" + value);//自然排序，字串本身實現了Comparator的介面
		}
	}
}

B:TreeMap<Student,String> //注意:自然排序和比較器排序

package cn.itcast_04;

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

/*
 * TreeMap<Student,String>
 * 鍵:Student
 * 值：String
 */
public class TreeMapDemo2 {
	public static void main(String[] args) {
		// 建立集合物件
		TreeMap<Student, String> tm = new TreeMap<Student, String>(
				new Comparator<Student>() {
					@Override
					public int compare(Student s1, Student s2) {
						// 主要條件
						int num = s1.getAge() - s2.getAge();
						// 次要條件
						int num2 = num == 0 ? s1.getName().compareTo(s2.getName()) : num;
						return num2;
					}
				});

		// 建立學生物件
		Student s1 = new Student("潘安", 30);
		Student s2 = new Student("柳下惠", 35);
		Student s3 = new Student("唐伯虎", 33);
		Student s4 = new Student("燕青", 32);
		Student s5 = new Student("唐伯虎", 33);

		// 儲存元素
		tm.put(s1, "宋朝");
		tm.put(s2, "元朝");
		tm.put(s3, "明朝");
		tm.put(s4, "清朝");
		tm.put(s5, "漢朝");

		// 遍歷
		Set<Student> set = tm.keySet();
		for (Student key : set) {
			String value = tm.get(key);
			System.out.println(key.getName() + "---" + key.getAge() + "---"
					+ value);
		}
	}
}

package cn.itcast_04;

public class Student {
	private String name;
	private int age;

	public Student() {
		super();
	}

	public Student(String name, int age) {
		super();
		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;
	}
}