scan.hasNext false应为true

Question

So I'm a beginner at programming and I'm trying to figure out what the problem is with the

following functions. The problem is with the scan.hasNext() method I have two println

statements ( one right after I make scan, and one on the second method ) telling me whether scan.hasNext() returns true or false . The weird thing is

that the code as it is now enters the while loop which is what should happen, but when I

delete one of the println statements it doesn't go in the loop and the other print

statement tells me scan.hasNext() is false .

This is weird because I change nothing except for erasing a print statement. Furthermore I

found if I add one more for a total of 3 print statements it will be false again, and if I

add a fourth it's true again, etc. I think I just don't understand how hasNext works since I

have no idea how to follow where the "cursor" should be.

public void createFile(String filename){    
    final File file = new File(filename);       
    try{
        scan = new Scanner(file);
        **System.out.println(scan.hasNext());**
        buff = new BufferedWriter(new FileWriter(filename), 1);         
    }
    catch(Exception e1){
        try{
            buff = new BufferedWriter(new FileWriter(filename));
            scan = new Scanner(file);
        }
        catch(Exception e2){
            System.out.println("Error trying to create file");
        }   
    }
}

public String readFile(){
    String fileContents = "";
    **System.out.println(scan.hasNext());**
    if(scan.hasNext())
        while(scan.hasNext())
            fileContents = fileContents + scan.next()+" "+scan.next()+" "+scan.next();
    return fileContents;

}

Answer 1

Okay so I figured it out. vishal_aim's suggestion helped me figure it out. The following line

buff = new BufferedWriter(new FileWriter(filename), 1);

was truncating my file back to zero size. the reason being is because I really meant to do this.

buff = new BufferedWriter(new FileWriter(filename, true));

Firstly I put one because I thought java automatically made 1 true when it asked for a boolean. Secondly I was trying to use a constructor of the FileWriter class that lets me append to the end of a file. If you don't include the true with your filename it will make a new file truncating anything in the file you have to 0. This was just a tired mistake I had forgotten if I needed to put the boolean on BufferedWriter or FileWriter. Also in case you're wondering the reason the BufferedWriter constructor wasn't giving me and error is because there is a constructor for it that takes an int, the int being the buffer size. Thank you all for your contribution.