Map练习！！！

最新推荐文章于 2020-11-12 21:53:53 发布

原创最新推荐文章于 2020-11-12 21:53:53 发布 · 659 阅读

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本文介绍了一种使用Java实现的学生信息存储方案，利用HashMap和TreeMap存储学生姓名、年龄及其对应的城市归属地。通过自定义Student类并重写equals、hashCode及compareTo方法确保了学生数据的唯一性和有序性。

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/*
每一个学生都有对应的归属地。
学生Student,地址String.
学生属性：姓名，年龄。
注意：姓名和年龄相同的视为同一个学生。
保证学生的唯一性。
*/
import java.util.*;
class Student implements Comparable<Student>
{
	private String name;
	private int age;
	Student(String name,int age)
	{
		this.name=name;
		this.age=age;
	}
	public void setAge(int age)
	{
		this.age=age;
	}
	public void setName(String name)
	{
		this.name=name;
	}
	public String getName()
	{
		return name;
	}
	public int getAge()
	{
		return age;
	}
	public int compareTo(Student s)
	{
		int num=new Integer(this.age).compareTo(new Integer(s.age));
		if (num==0)
		{
			return this.name.compareTo(s.name);
		}
		return num;
	}
	public boolean equals(Object obj)
	{
		if (!(obj instanceof Student))
		{
			throw new ClassCastException("类型不匹配！！！");
		}
		Student s=(Student)obj;
		return this.name.equals(s.name)&&this.age==s.age;
	}
	public int hashCode()
	{
		return this.name.hashCode()+age*39;
	}
}
class MapTest
{
	public static void main(String[] args)
	{
		HashMap<Student,String>hm=new HashMap<Student,String>();
		hm.put(new Student("xxc1",10),"hangzhou");
		hm.put(new Student("xxc2",20),"beijing");
		hm.put(new Student("xxc3",30),"chongqing");
		hm.put(new Student("xxc4",40),"zhongnanhai");
		//第一种取出方式,用keySet();
		Set<Student>keySet=hm.keySet();
		Iterator<Student> t=keySet.iterator();
		while (t.hasNext())
		{
			Student s=t.next();
			String s1=hm.get(s);
			System.out.println(s.getName()+"====="+s.getAge()+"=="+s1);
		}
		System.out.println("===================================================================");
		//第二种取出方式，用entrySet();
		Set<Map.Entry<Student,String>> me=hm.entrySet();
		Iterator<Map.Entry<Student,String>>t1=me.iterator();
		while (t1.hasNext())
		{
			Map.Entry<Student,String> me1=t1.next();
			Student s=me1.getKey();
			String s1=me1.getValue();
			System.out.println(s.getName()+"=="+s.getAge()+"=="+s1);
		}
	}
}
============================================================================================================
import java.util.*;
class TreeMapTest
{
	public static void main(String[] args)
	{
		TreeMap<Student,String>tm=new TreeMap<Student,String>(new MyCom());
		tm.put(new Student("xxc1",60),"hangzhou");
		tm.put(new Student("xxc5",10),"beijing");
		tm.put(new Student("xxc8",90),"chongqing");
		tm.put(new Student("xxc4",40),"zhongnanhai");
		Set<Map.Entry<Student,String>>entry=tm.entrySet();
		Iterator<Map.Entry<Student,String>> t=entry.iterator();
		while (t.hasNext())
		{
			Map.Entry<Student,String> me=t.next();
			Student s=me.getKey();
			String s1=me.getValue();
			System.out.println(s.getName()+"="+s.getAge()+"="+s1);
		}
	}
}
class MyCom implements Comparator<Student>
{
	public int compare(Student s1,Student s2)
	{
		int num=s1.getName().compareTo(s2.getName());
		if (num==0)
		{
			return new Integer(s1.getAge()).compareTo(new Integer(s2.getAge()));
		}
		return num;
	}
}
/*
用TreeMap集合对元素进行排序，方法和TreeSet一样！！！

*/