TreeMap和Comparable接口

Posted 2023-01-05 lujunlong

备注：HashMap线程不安全，效率高，允许key、value为空

HasTable线程安全、效率低、不允许key或value为空

 

TreeMap在存储时会自动调用comparable方法进行排序，当key为类时可自行调用comparable接口

 

范例：

package cn.study.lu.four;

import java.util.TreeMap;

public class TestTreeMap
public static void main(String[] args)
TreeMap<Integer, String> str1 = new TreeMap<Integer, String>();

str1.put(1001, "aaa");
str1.put(333, "bbb");
str1.put(181, "ccc");
str1.put(9991, "ddd");
for (int k:str1.keySet())
System.out.println(k +"---"+str1.get(k));

System.out.println(str1);

TreeMap<emp, String> str2 = new TreeMap<emp, String>();
str2.put(new emp(1001, "张三", 10000),"aaa");
str2.put(new emp(1002, "王五", 60000),"bbb");
str2.put(new emp(1003, "里斯", 20000),"ccc");
str2.put(new emp(1004, "赵六", 20000),"ddd");
for(emp i:str2.keySet())
System.out.println(i+"---"+str2.get(i));

class emp implements Comparable<emp>
int id;
String name;
int salary;
public emp(int id, String name, int salary)
super();
this.id = id;
this.name = name;
this.salary = salary;



public String toString()
return ("id:"+id+",name:"+name+",salary:"+salary);


public int compareTo(emp o)
if (this.salary>o.salary)
return 1;
else if(this.salary<o.salary)
return -1;
else if (this.id>o.id)
return 1;
else if(this.id<o.id)
return-1;
else
return 0 ;