List to Map

Here is and easy way to convert List to a Map where the index is used as key :

import java.util.*;

public class Test {
  
 public static <ARG> void say(ARG arg) { System.out.println(arg); }

 public static HashMap<Integer, ?> list2map(List lst) {
    HashMap map = new HashMap();
	for (int i=0; i < lst.size(); i++) {
		map.put(i, lst.get(i));
	}
	return map;
  }

  public static void main(String[] args) {
      List a = Arrays.asList( 1,2,3,4 );
      say(a);
      say(list2map(a));
  }
}

Output:

[1, 2, 3, 4]
{0=1, 1=2, 2=3, 3=4}

You can directly test it (the code already setup for you) here in OneCompiler editor : https://onecompiler.com/java/3xh55parb

Tags: hashmaplistmap