Retrieve all the keys from HashMap in Java

Java 8Object Oriented ProgrammingProgramming

Let’s say the following is our HashMap −

HashMap<Integer, String>map = new HashMap<Integer, String>();
map.put(10, "A");
map.put(20, "B");
map.put(30, "C");
map.put(40, "D");
map.put(50, "E");
map.put(60, "F");
map.put(70, "G");
map.put(80, "H");

To retrieve all the keys, iterator through each and every key-value pair −

Set<Integer>set = map.keySet();
Iterator<Integer>i = set.iterator();
while (i.hasNext()) {
   Integer res = i.next();
   System.out.println(res + ": " + map.get(res));
}

Example

 Live Demo

import java.util.HashMap;
import java.util.Iterator;
import java.util.Set;
public class Demo {
   public static void main(String[] args) {
      HashMap<Integer, String>map = new HashMap<Integer, String>();
      map.put(10, "A");
      map.put(20, "B");
      map.put(30, "C");
      map.put(40, "D");
      map.put(50, "E");
      map.put(60, "F");
      map.put(70, "G");
      map.put(80, "H");
      Set<Integer>set = map.keySet();
      Iterator<Integer>i = set.iterator();
      while (i.hasNext()) {
         Integer res = i.next();
         System.out.println(res + ": " + map.get(res));
      }
   }
}

Output

80: H
50: E
20: B
70: G
40: D
10: A
60: F
30: C
raja
Updated on 30-Jul-2019 22:30:25

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