public class Main {
  public static void main(String[] args) throws Exception {
    String fileName = "c:\\temp\\test.bmp";
    String[] commands = { "cmd.exe", "/c", "start", "\"DummyTitle\"",
        "\"" + fileName + "\"" };
    Process p = Runtime.getRuntime().exec(commands);
    p.waitFor();
    System.out.println("Done.");
  }
}

Or, use the Desktop class.

import java.awt.Desktop;
import java.io.File;
/*from  w  w  w  . j  a v  a 2  s .  com*/
public class Main {
  public static void main(String[] args) throws Exception {
    File f = new File("c:\\temp\\test.bmp");
    Desktop dt = Desktop.getDesktop();
    dt.open(f);
    System.out.println("Done.");
  }
}