LinkedHashMap is a predefined class in Java that is similar to HashMap, contains a key and its respective value. Unlike HashMap, In LinkedHashMap insertion order is preserved. The task is to print all the Keys present in our LinkedHashMap in java. We have to iterate through each Key in our LinkedHashMap and print It.
Example :
Input : Key- 1 : Value-5
Key- 29 : Value-13
Key- 14 : Value-10
Key- 34 : Value-2
Key- 55 : Value-6
Output: 1, 29, 14, 34, 55
Method 1: Use for-each loop to iterate through LinkedHashMap. For each iteration, we print the respective key using getKey() method.
for(Map.Entry<Integer,Integer>ite : LHM.entrySet())
System.out.print(ite.getKey()+", ");
Example 1:
Java
// Java program to print all keys of the LinkedHashMap import java.util.*;import java.io.*; class GFG { public static void main(String[] args) { // create a linkedhashmap LinkedHashMap<Integer, Integer> LHM = new LinkedHashMap<>(); // Add mappings LHM.put(1, 5); LHM.put(29, 13); LHM.put(14, 10); LHM.put(34, 2); LHM.put(55, 6); // print keys using getKey() method for (Map.Entry<Integer, Integer> ite : LHM.entrySet()) System.out.print(ite.getKey() + ", "); }} |
Output
1, 29, 14, 34, 55,
Example 2:
Java
// Java program to print all keys of the LinkedHashMap import java.util.*;import java.io.*; class GFG { public static void main(String[] args) { // create a linkedhashmap LinkedHashMap<String, String> LHM = new LinkedHashMap<>(); // Add mappings LHM.put("Geeks", "Geeks"); LHM.put("for", "for"); LHM.put("Geeks", "Geeks"); // print keys using getKey() method for (Map.Entry<String, String> ite : LHM.entrySet()) System.out.print(ite.getKey() + ", "); }} |
Output
Geeks, for,
Method 2: (Using keySet() method)
Syntax:
hash_map.keySet()
Parameters: The method does not take any parameters.
Return Value: The method returns a set having the keys of the hash map.
Java
import java.io.*;import java.util.*; class GFG { public static void main(String[] args) { // create an instance of linked hashmap LinkedHashMap<String, String> lhm = new LinkedHashMap<String, String>(); lhm.put("One", "Geeks"); lhm.put("Two", "For"); lhm.put("Three", "Geeks"); // get all keys using the keySet method Set<String> allKeys = lhm.keySet(); // print keys System.out.println(allKeys); }} |
Output
[One, Two, Three]
