HashMap知识点整理

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以HashMap<String, Car>为例，验证HashMap中的插入元素、删除元素、查找元素等方法。示例所用的HashMap<key,value>的key 是carID，

public class Car {
   String CarID;
   int maxVelocity;
   
   //重写了equals方法
   public boolean equals(Car car) {
		if(this.CarID.equals(car.getCarID())) return true;
		else return false;
	}
   
   public Car(String string, int i) {
	  CarID=string;
	  maxVelocity=i;
   }
   public String getCarID() {
	  return CarID;
   }
   public void setCarID(String carID) {
	  CarID = carID;
   }
   public int getMaxVelocity() {
	  return maxVelocity;
   }
   public void setMaxVelocity(int maxVelocity) {
	  this.maxVelocity = maxVelocity;
   }
   
}

import java.util.HashMap;

public class Solution
{
	public static void main(String[] args)
	{
		HashMap<String, Car> cars = new HashMap<String, Car>();
		Car car1 = new Car("01", 20);
		Car car2 = new Car("02", 10);
		Car car3 = new Car("03", 30);
		Car car4 = new Car("01", 20);

		cars.put(car1.CarID, car1);
		cars.put(car2.CarID, car2);
		cars.put(car3.CarID, car3);
		cars.put(car4.CarID, car4);

		/**
		 * 添加元素
		 */

		/**
		 * 删除元素
		 */

		/**
		 * 查找元素
		 */

	}
}

1、添加元素

cars.put(car1.CarID, car1); // 放入key为carID,值为car的实例对象

2、删除元素

remove(key); 按key删除

cars.remove(car1.CarID);

remove(key,value); 按key和value删除

cars.remove(car1.CarID,car1);

3、查找元素

get(key); 查找key对应的value

cars.get(car1.CarID);

4、判断键值

containsKey(key); 判断是否有相应的键值

cars.containsKey(car1.CarID);