1 package Maptest01;
2
3 import java.util.Collection;
4 import java.util.HashMap;
5 import java.util.Map;
6 import java.util.Set;
7
8 /**
9 * FileName: MapDemo01
10 * Author: lps
11 * Date: 2022/4/14 11:07
12 * Sign:刘品水 Q：1944900433
13 */
14 public class MapDemo01 {
15 public static void main(String[] args) {
16 //添加元素：无序 不重复 无索引
17 //Map<String, Integer> maps = new HashMap<>();//一行经典代码
18 Map<String, Integer> maps = new HashMap<>();//一行经典代码
19 maps.put("刘品水",3);
20 maps.put("枸杞",13);
21 maps.put("Java",1);
22 maps.put("Java",100);
23 maps.put("手机",50);
24 //maps.put(null,null);
25
26 //2.清空集合
27 // maps.clear();
28 // System.out.println(maps);
29
30 //3.查看是否为空
31 System.out.println(maps.isEmpty());
32
33 //4.根据键获取值 public V get(Object key)
34 Integer key = maps.get("Java");
35 System.out.println(key);
36 //System.out.println(maps.get("Java"));
37
38 //5.根据键删除整个元素 （删除键会返回键的值）
39 Integer key1 = maps.remove("手机");
40 System.out.println(key1);
41 System.out.println(maps);
42
43 //6.判断是否包含某个键 包含返回true 反之
44 System.out.println(maps.containsKey("Java"));
45 boolean mobilephone = maps.containsKey("手机");
46 System.out.println(mobilephone);
47
48
49 //7.判断是否包含某个值
50 System.out.println(maps.containsValue(13));
51
52 //8.获取全部键的集合 public Set<K> keyset()
53 Set<String> strings = maps.keySet();
54 System.out.println(strings);
55
56 //9.获取所有值的集合Collection<V> values();
57 Collection<Integer> values = maps.values();
58 System.out.println(values);
59
60 //10.集合的大小
61 int size = maps.size();
62 System.out.println(size);
63
64 //11.合并其他Map集合
65 HashMap<String, Integer> map1 = new HashMap<>();
66 map1.put("Java1",50);
67 map1.put("Java2",2);
68 HashMap<String, Integer> map2 = new HashMap<>();
69 map2.put("Java2",50);
70 map2.put("Java3",2);
71 map1.putAll(map2);//把集合map2的元素拷贝到map1中
72 System.out.println(map1);
73 System.out.println(map2);
74
75
76 }
77 }
