How to remove duplicates from list in java

package govind;

import java.util.ArrayList;
import java.util.HashSet;
import java.util.Iterator;
import java.util.LinkedHashSet;

public class RemoveDuplicate {

public static void main(String[] args) {
ArrayList<String> al=new ArrayList<>();
al.add("govind");
al.add("ballabh");
al.add("khan");
al.add("java");
al.add("technology");
al.add("govind");
al.add("java");
System.out.println(al);
System.out.println("Remove duplicate using HashSet but order does not maintain ");
HashSet< String> hs=new HashSet<>(al);
System.out.println(hs);
System.out.println("Remove duplicate using LinkedHashSet but order maintain ");
LinkedHashSet< String> lhs=new LinkedHashSet<>(al);
System.out.println(lhs);
System.out.println("Remove duplicate using contains method");
ArrayList<String> ul=new ArrayList<>();
for(String t:al)
{
if(!ul.contains(t))
{
ul.add(t);
}
}

Iterator<String> it = ul.iterator();
while (it.hasNext()) {
String s= (String) it.next();
System.out.println(s);

}





}

}

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o/p:--------------------------------------
[govind, ballabh, khan, java, technology, govind, java]
Remove duplicate using HashSet but order does not maintain
[java, ballabh, govind, khan, technology]
Remove duplicate using LinkedHashSet but order maintain
[govind, ballabh, khan, java, technology]
Remove duplicate using contains method
govind
ballabh
khan
java
technology