ArrayList Only Adding 1 Item Even Though There Are Multiple Items (Setting Data To Files)

I managed to retrieve data, and set data in my own ways in which I like. But my problem is, if the file does not contain anything (fully empty), when I try to use my

set("", "");

method, it only sets the last one that is called.

Example:

set("section1", "section1Item");
set("section2", "section2Item");
set("section3", "section3Item");

Only section3 would get set, and not the others.

Otherwise, if the file contained a section already, then each section (section1, section2, section3) would get set.

Here's how I set the data to the file:

public static void set(String section, String data) {
files.openFileWriter();
files.file.delete();
reCreateFile();
String beforeItem = section + ":" + files.dataList.get(section);

[code]....

And here is how a retrieve the data and set them to my arraylist/hashmap:

public void getData() {
String line = null;
openFileReader();
StringBuffer sb = new StringBuffer();

[code]....