/* package whatever; // don't place package name! */
 
import java.util.*;
import java.lang.*;
import java.io.*;
 
import java.util.stream.* ;
 
/* Name of the class has to be "Main" only if the class is public. */
class Ideone
{
	public static void main (String[] args) throws java.lang.Exception
	{
		System.out.println( Ideone.reverse( "dog🐶" ) );
	}
 
	public static String reverse ( String s ) {
        List < Integer > codePoints = s.codePoints().boxed().collect( Collectors.toCollection( ArrayList :: new ) );
        Stack < Integer > stack = new Stack();
        int i;
        for ( i = 0; i < codePoints.size() ; i++ ) {
            stack.push( codePoints.get( i ) );
        }
        i = 0;
        while ( ! stack.isEmpty() ) {
            codePoints.set( i++ , stack.pop() );
        }
        String output = codePoints.stream().collect( StringBuilder :: new , StringBuilder :: appendCodePoint , StringBuilder :: append ).toString();
        return output;
    }
}

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