Java how to "\" to "\\"

1         FileChooser fileChooser = new FileChooser();
2         fileChooser.setTitle("选择你要查看的文件");
3         File file = fileChooser.showOpenDialog(null);
4         String path = file.getPath().toString();
5         String str = path.replaceAll("\\\\","\\\\\\\\");

      When I want to go through FileChooser to open a picture, and by Imageview time display, found it   file.getPath ();   can not be used directly, need to convert the format to use File: D: \\ * PNG.    , file.getPath () Gets the path to D:. \ * PNG , which is obviously undesirable. So by String inside replaceAll this method the "\" replaced by "\\"   , but can not be found directly. Later Baidu, a   "\"   need four   "\"   to function properly replaced.