一、简介
- Map就是用来存储“键(key)-值(value)”对的.
- 通过键寻找value,所以键不能重复.
- 数组的本质也是一种键值对,区别就是索引一般是数字,而Map的Key可以是任意对象(字符串,数字),相当于把数组的索引范围扩的更大,使用更方便.
- 实际开发中较为常用.
二、Map的常用方法实例
- (1)存储数据(V put(K key, V value))
Map<Integer,String> map = new HashMap<>(16);map.put(1,"a");map.put(2,"b");map.put(3,"c");map.put(4,"d");map.put(5,"e");map.put(6,"f");map.put(7,"g");map.put(8,"h");map.put(9,"i");- (2)取出数据(V get(Object key))
String s = map.get(1);System.out.println(s);
- (3)添加对象操作
import java.util.HashMap;
import java.util.Map;/*** @author liuyangos8888*/
public class MapHasObject {public static void main(String[] args) {Employee e1 = new Employee(1001, "张三", 50000);Employee e2 = new Employee(1002, "李四", 5000);Employee e3 = new Employee(1003, "龙五", 6000);Employee e4 = new Employee(1001, "五六", 7000);Map<Integer, Employee> map = new HashMap<>();map.put(1001, e1);map.put(1002, e2);map.put(1003, e3);map.put(1001, e4);Employee emp = map.get(1001);System.out.println(emp.getEmployeeName());System.out.println(map);}}/*** 新建职员对象*/
class Employee {/*** 工号*/private int id;/*** 姓名*/private String employeeName;/*** 薪资*/private double salary;public Employee(int id, String employeeName, double salary) {this.id = id;this.employeeName = employeeName;this.salary = salary;}public String getEmployeeName() {return employeeName;}public void setEmployeeName(String employeeName) {this.employeeName = employeeName;}public int getId() {return id;}public void setId(int id) {this.id = id;}public double getSalary() {return salary;}public void setSalary(double salary) {this.salary = salary;}@Overridepublic String toString() {return "Employee{" +"id=" + id +", employeeName='" + employeeName + '\'' +", salary=" + salary +'}';}
}结果:
