chars-vs-bytes.java

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.nio.charset.StandardCharsets;

public class Foo {

    public static void main(String[] args) throws IOException {
        final char c = 'ñ';
        final ByteArrayOutputStream baos = new ByteArrayOutputStream();
        final OutputStreamWriter writer = new OutputStreamWriter(baos);
        writer.write(c);
        writer.close();
        final String string = baos.toString("UTF-8");
        System.out.printf("string: %s%n", string);
        System.out.printf("length: %s%n", string.length());
        System.out.printf(" chars: %s%n", string.toCharArray().length);
        System.out.printf(" bytes: %s%n", baos.toByteArray().length);
        System.out.printf(" bytes: %s%n", string.getBytes(StandardCharsets.UTF_8).length);
    }
}

output.txt

string: ñ
length: 1
 chars: 1
 bytes: 2
 bytes: 2