Reverse A String in java

public static char[] reverse(String s)
{
char[] mainString = s.toCharArray();
for(int i=0;i<s.length()/2;i++)
{
char temp = mainString[i];
mainString[i] = mainString[s.length()-i-1];
mainString[s.length()-i-1] = temp;
}
return mainString;
}


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String s = "Hello";
for(int i = 0; i < s.length(); i++)
{
   s = s.substring(1, s.length() - i) + s.charAt(0) + s.substring(s.length() - i);
}
System.out.println(s);