File from = new File(Environment.getExternalStorage().getAbsolutePath()+"/kaic1/imagem.jpg");
File to = new File(Environment.getExternalStorage().getAbsolutePath()+"/kaic2/imagem.jpg");
from.renameTo(to);

File file1 = new File("mnt/sdcard/kaic1/imagem.jpg");
File file2 = new File("mnt/sdcard/Kaic2/imagem.jpg");

file1.renameTo(file2);