PROGRAM TO CHECK UNIQUE NUMBER IN JAVA

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import java.util.*;
import java.io.*;
public class IsUnique
{
public static boolean
isUniqueUsingHash(String word)
{char[] chars = word.toCharArray();
Set<Character> set = new
HashSet<Character>();
for (char c : chars)
if (set.contains(c))
return false;
else
set.add(c);
return true;
}
public static boolean
isUniqueUsingSort(String word)
{char[] chars = word.toCharArray();
if (chars.length <= 1)
return true;
Arrays.sort(chars);
char temp = chars[0];
for (int i = 1; i < chars.length; i++)
{if (chars[i] == temp)
return false;
temp = chars[i];
}
return true;
}
public static void main(String[] args)
throws IOException
{
System.out.println(isUniqueUsingHash("? "Unique" : "Not Unique");
System.out.println(isUniqueUsingSort("? "Unique" : "Not Unique");
}
}