Java HashMap containsValue() Method
Java HashMapThe containsValue() method checks whether the specified value has a corresponding mapping in the hashMap.
The syntax of the containsValue() method is:
hashmap.containsValue(Object value)
Note:hashmap is an object of the HashMap class.
Parameter description:
- value - the value
Return Value
Returns true if the specified value has a corresponding mapping in the hashMap, otherwise returns false.
Example
The following example demonstrates the usage of the containsValue() method:
Example
import java.util.HashMap;
class Main {
public static void main(String[] args) {
// Create a HashMap
HashMap<Integer, String> sites = new HashMap<>();
// Add some elements to the HashMap
sites.put(1, "Google");
sites.put(2, "Example");
sites.put(3, "Taobao");
System.out.println("sites HashMap: " + sites);
// Check whether the value "Java" exists in the mapping
if(sites.containsValue("Example")) {
System.out.println("Example exists in sites");
}
}
}
class Main {
public static void main(String[] args) {
// Create a HashMap
HashMap<Integer, String> sites = new HashMap<>();
// Add some elements to the HashMap
sites.put(1, "Google");
sites.put(2, "Example");
sites.put(3, "Taobao");
System.out.println("sites HashMap: " + sites);
// Check whether the value "Java" exists in the mapping
if(sites.containsValue("Example")) {
System.out.println("Example exists in sites");
}
}
}
The output of the above program is:
sites HashMap: {1=Google, 2=Example, 3=Taobao}
Example 存在于 sites 中
For values that do not exist, we can perform an insertion operation:
Example
import java.util.HashMap;
class Main {
public static void main(String[] args) {
// Create a HashMap
HashMap<Integer, String> sites = new HashMap<>();
// Add some elements to the HashMap
sites.put(1, "Google");
sites.put(2, "Example");
sites.put(3, "Taobao");
System.out.println("sites HashMap: " + sites);
// Check whether the value "Wiki" exists; if not, insert the key/value pair
// Use the ! symbol to negate the boolean result
if(!sites.containsValue("Wiki")) {
sites.put(4, "Wiki");
}
System.out.println("Updated sites HashMap: " + sites);
}
}
class Main {
public static void main(String[] args) {
// Create a HashMap
HashMap<Integer, String> sites = new HashMap<>();
// Add some elements to the HashMap
sites.put(1, "Google");
sites.put(2, "Example");
sites.put(3, "Taobao");
System.out.println("sites HashMap: " + sites);
// Check whether the value "Wiki" exists; if not, insert the key/value pair
// Use the ! symbol to negate the boolean result
if(!sites.containsValue("Wiki")) {
sites.put(4, "Wiki");
}
System.out.println("Updated sites HashMap: " + sites);
}
}
The output of the above program is:
sites HashMap: {1=Google, 2=Example, 3=Taobao}
Updated sites HashMap: {1=Google, 2=Example, 3=Taobao, 4=Wiki}
Note:We can also useHashMap putIfAbsent() methodto perform the same operation.
Other extensions