Map集合常用API复习

package Maptest01;

import java.util.Collection;
import java.util.HashMap;
import java.util.Map;
import java.util.Set;

/**
 * FileName: MapDemo01
 * Author:   lps
 * Date:     2022/4/14 11:07
 * Sign:刘品水 Q：1944900433
 */
public class MapDemo01 {
    public static void main(String[] args) {
        //添加元素：无序 不重复 无索引
        //Map<String, Integer> maps = new HashMap<>();//一行经典代码
        Map<String, Integer> maps = new HashMap<>();//一行经典代码
        maps.put("刘品水",3);
        maps.put("枸杞",13);
        maps.put("Java",1);
        maps.put("Java",100);
        maps.put("手机",50);
        //maps.put(null,null);

        //2.清空集合
//        maps.clear();
//        System.out.println(maps);

        //3.查看是否为空
        System.out.println(maps.isEmpty());

        //4.根据键获取值 public V get(Object key)
        Integer key = maps.get("Java");
        System.out.println(key);
        //System.out.println(maps.get("Java"));

        //5.根据键删除整个元素 （删除键会返回键的值）
        Integer key1 = maps.remove("手机");
        System.out.println(key1);
        System.out.println(maps);

        //6.判断是否包含某个键 包含返回true 反之
        System.out.println(maps.containsKey("Java"));
        boolean mobilephone = maps.containsKey("手机");
        System.out.println(mobilephone);


        //7.判断是否包含某个值
        System.out.println(maps.containsValue(13));

        //8.获取全部键的集合 public Set<K> keyset()
        Set<String> strings = maps.keySet();
        System.out.println(strings);

        //9.获取所有值的集合Collection<V> values();
        Collection<Integer> values = maps.values();
        System.out.println(values);

        //10.集合的大小
        int size = maps.size();
        System.out.println(size);

        //11.合并其他Map集合
        HashMap<String, Integer> map1 = new HashMap<>();
        map1.put("Java1",50);
        map1.put("Java2",2);
        HashMap<String, Integer> map2 = new HashMap<>();
        map2.put("Java2",50);
        map2.put("Java3",2);
        map1.putAll(map2);//把集合map2的元素拷贝到map1中
        System.out.println(map1);
        System.out.println(map2);


    }
}