Question

How to remove duplicates from ArrayList in Java

Answer 1

import java.util.*;
   
public class MyClass {
    public static <T> void removeDuplicates(ArrayList<T> al) { 
        Set<T> set = new LinkedHashSet<>(); 
  
        set.addAll(al); 
  
        al.clear(); 

        al.addAll(set); 
    } 
    public static void main(String args[]) {
        ArrayList<Integer> al = new ArrayList<>(Arrays.asList(3, 1, 6, 4, 3, 3, 6, 8, 3, 3, 3)); 

        System.out.println(al); 
         
        removeDuplicates(al); 
 
        System.out.println(al); 
 
    }
}
   
   
   
   
/*
run:
   
[3, 1, 6, 4, 3, 3, 6, 8, 3, 3, 3]
[3, 1, 6, 4, 8]

*/

 

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