SystemParametersInfo with SPI_SETDESKWALLPAPER not working

I've never actually tried to use native methods before, so bear with me.

I am trying to use SystemParametersInfo to change my wallpaper with a java program, and it's not working. The code compiles and runs, but nothing happens.

public class MagicWallPaper
{
    public static native int SystemParametersInfo(int uiAction, int uiParam, String pvParam, int fWinIni);
    
    static
    {
        System.loadLibrary("user32");
    }

    public static void main(String args[])
    {
        
        String dan = "C:\\Users\\1023\\Desktop\\DanMyer.jpg";
        SystemParametersInfo(20, 0, dan, 1);
    }
}

I've tried using SystemParametersInfoA and SystemParametersInfoW, as well as passing both 0 and 1 for the last parameter. Microsoft docs don't help much, they just say:

Note When the SPI_SETDESKWALLPAPER flag is used, SystemParametersInfo returns TRUE unless there is an error (like when the specified file doesn't exist).

All I have is this and user32.dll in the same folder.