Java HashMap keySet() Method
Java HashMapThe keySet() method returns a Set view of all keys contained in the map.
The syntax of the keySet() method is:
hashmap.keySet()
Note:hashmap is an object of the HashMap class.
Parameter Description:
- None
Return Value
Returns a Set view of all keys contained in the map.
Example
The following example demonstrates the use of the keySet() 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);
// Return a set view of all keys
System.out.println("Keys: " + sites.keySet());
}
}
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);
// Return a set view of all keys
System.out.println("Keys: " + sites.keySet());
}
}
Executing the above program outputs:
sites HashMap: {1=Google, 2=Example, 3=Taobao}
Keys: [1, 2, 3]
The keySet() method can be used with a for-each loop to iterate over all keys in the HashMap.
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);
// Return a set view of all keys
System.out.println("Keys: " + sites.keySet());
// keySet() returns a set view of all keys
// for-each loop accesses each key in the view
for(int key: sites.keySet()) {
// Output each key
System.out.print(key + ", ");
}
}
}
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);
// Return a set view of all keys
System.out.println("Keys: " + sites.keySet());
// keySet() returns a set view of all keys
// for-each loop accesses each key in the view
for(int key: sites.keySet()) {
// Output each key
System.out.print(key + ", ");
}
}
}
Executing the above program outputs:
sites HashMap: {1=Google, 2=Example, 3=Taobao}
Keys: [1, 2, 3]
1, 2, 3,
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