双列集合Map的特点

import java.util.HashMap;
import java.util.Map;
/**
 * 双列集合Map的特点:
 * 如果键是自定义对象,必须重写equals和hashcode方法  
 * @author 罗摩衔那
 *
 */
public class Demo_Maps
{
  public static void main(String[] args) 
  {     
    //自定义一个容器
      Map<IdCard,people>map=new HashMap<>();
      //初始两个键
      IdCard idcard1=new IdCard("张三丰", "001");
      IdCard idcard2=new IdCard("张三丰", "001");
      //对应键值
      map.put(idcard1, new people("张三丰", "男", "200"));
      map.put(idcard2, new people("张三丰", "男", "100"));
      System.out.println(map);
  }
}

class people
{
    private String name;
    private String gender;
    private String age;
    
    public people(String name,String gender,String age)
    {
        this.name=name;
        this.gender=gender;
        this.age=age;
    }

    @Override
    public String toString() {
        return "name=" + name + ", gender=" + gender + ", age=" + age ;
    }

    @Override
    public int hashCode() {
        final int prime = 31;
        int result = 1;
        result = prime * result + ((age == null) ? 0 : age.hashCode());
        result = prime * result + ((gender == null) ? 0 : gender.hashCode());
        result = prime * result + ((name == null) ? 0 : name.hashCode());
        return result;
    }

    @Override
    public boolean equals(Object obj) {
        if (this == obj)
            return true;
        if (obj == null)
            return false;
        if (getClass() != obj.getClass())
            return false;
        people other = (people) obj;
        if (age == null) {
            if (other.age != null)
                return false;
        } else if (!age.equals(other.age))
            return false;
        if (gender == null) {
            if (other.gender != null)
                return false;
        } else if (!gender.equals(other.gender))
            return false;
        if (name == null) {
            if (other.name != null)
                return false;
        } else if (!name.equals(other.name))
            return false;
        return true;
    }    
    
}

class IdCard
{
    private String name;
    private String ID;
    public  IdCard(String name,String ID)
    {
        this.name=name;
        this.ID=ID;        
    }
    @Override
    public String toString() {
        return "name=" + name + ", ID=" + ID ;
    }
    @Override
    public int hashCode() {
        final int prime = 31;
        int result = 1;
        result = prime * result + ((ID == null) ? 0 : ID.hashCode());
        result = prime * result + ((name == null) ? 0 : name.hashCode());
        return result;
    }
    @Override
    public boolean equals(Object obj) {
        if (this == obj)
            return true;
        if (obj == null)
            return false;
        if (getClass() != obj.getClass())
            return false;
        IdCard other = (IdCard) obj;
        if (ID == null) {
            if (other.ID != null)
                return false;
        } else if (!ID.equals(other.ID))
            return false;
        if (name == null) {
            if (other.name != null)
                return false;
        } else if (!name.equals(other.name))
            return false;
        return true;
    }
}

import java.util.HashMap;
import java.util.Map;
/**
 * 双列集合Map的特点:
 *  键值对只能是意义对应
 *     添加键值对的时候出现了键重复,新的值会把对应的之前的值覆盖
 *   
 * @author 罗摩衔那
 *
 */
public class Demo_Maps
{
  public static void main(String[] args) 
  {
     Map<String,String>map=new HashMap<>();
     map.put("001", "刘亦菲");
     map.put("002", "迪丽热巴");
     System.out.println(map);
     map.put("001", "赵灵儿");
     System.out.println(map);
  }
}