Append text to files using FileWriter

I am trying to append new line of text for different json files. But for some reason, each json file only has one line after the below code is executed but it shouldn't. 

Node confNode = session.getNode("/etc");
Node reportFileNode;
Node contentNode;
for (int jIndex = 0; jIndex < array.length(); jIndex++){
    String title= array.getJSONObject(jIndex).getString("title");
    File file = File.createTempFile( title,".json");
    FileWriter fw = new FileWriter(file, true);
    fw.append(array.getJSONObject(jIndex).toString() + "\n");
    fw.close();
    if (confNode.hasNode(  title+".json")) {
        reportFileNode = confNode.getNode(title+ ".json");
        contentNode = reportFileNode.getNode("jcr:content");
    } else {
        reportFileNode = confNode.addNode(title+".json", "nt:file");
        contentNode = reportFileNode.addNode("jcr:content", "nt:unstructured");
    }
    FileInputStream fileInputStream = new FileInputStream(file);
    Binary contentValue = session.getValueFactory().createBinary(fileInputStream);
    contentNode.setProperty("jcr:data", contentValue);
}

 I already used "append" as well as adding "\n" to the file. Am I missing something? Thanks!