A brief introduction to the use of maps in Java

Public interface Map< K, V>

Objects that map keys to values. A map cannot contain duplicate keys; Each key can map to at most one value.

 import javautilHashMap;
 import javautilMap;
 public class Test {
   public static void main(String[] args) {
     Map map = new HashMap();//Declare a Map
     mapput("s", " Ha ha ");//Put a value in a map: a map is stored as key-value
     String str = mapget("s")toString();//Map gets the value of key "s"
     Systemoutprintln(str);
   }
 }

Output: haha

Map key-value pairs, where values are typically stored as objects.

Common method in hashmap, put(object key,object value); Associates the specified value with the specified key in this map

Get (object key); // find the corresponding value according to the key value.

Check whether the key exists: containsKey(object key)

Check whether the value exists: containsValue(object value)

The feature of a Map is key-value matching

 import java.util.HashMap;
 import java.util.Map;
 public class Test {
   public static void main(String[] args) {
     Map map = new HashMap();
     String key = "java";
     String key = "java";
     map.put(key, "java The value of the ");
     map.put(key, "java The value of the ");
     System.out.println(map.get(key));
     System.out.println(map.get(key));
   }
 }

Output:

The value of the java1
The value of the java2