Question

I’m looking to create an array that will be able to change size over time because the size of the array is unpredictable and I don’t want to create a huge random number that will waste memory so every time a button is pressed I need the array to grow by one.

private String[][] lyricLineInfo = new String[x][5];

In the place of x is where the array must grow upon the button push and 5 is a constant. So I need the x button to grow by one without overflowing. Can I do it by using something like this?

lyricLineInfo[lyricLineInfo.length + 1][4] = fieldLyrics.getText();

Anyways thanks in advance!

Answer 1

Use an ArrayList<String[]> (see the docs here). It will grow automatically. (It uses an internal array that doesn’t actually grow by just 1 when it needs to grow. Since growing is an expensive operation, it grows by some larger amount so it can absorb a few more items before having to grow again.)

EDIT

For example, here’s how you could recode the two lines of your original post:

private ArrayList<String[]> lyricLineInfo = new ArrayList<String[]>();

lyricLineInfo.add(fieldLyrics.getText());

The second line assumes that fieldLyrics.getText() returns a String[]. If I misunderstood your intent and it returns a String, then you could do the following:

String[] nextStrings = new String[5];
nextStrings[4] = fieldLyrics.getText();
lyricLineInfo.add(nextStrings);

If the second index isn’t always 5 long, you can also have an ArrayList of ArrayLists:

private ArrayList<ArrayList<String>> lyricLineInfo
    = new ArrayList<ArrayList<String>>();

Then you could lyricLineInfo.add(new ArrayList<String>()); to extend the array.

EDIT 2

@clankfan1 – In your comment, you asked how to do a particular operation. Let’s say we’re using the ArrayList<ArrayList<String>> structure. It would go something like this:

ArrayList<ArrayList<String>> lyricLineInfo = new ArrayList<ArrayList<String>>();

ArrayList<String> line = new ArrayList<String>();
line.add("true");
line.add("true");
line.add("0.0");
line.add("5.0");
line.add("First Line");
lyricLineInfo.add(line);
line = new ArrayList<String>(); // don't use clear(): need a new object here
line.add("false");
line.add("false");
line.add("5.0");
line.add("10.0");
line.add("Second Line");
lyricLineInfo.add(line);

String secondLineTitle = lyricLineInfo.get(1).get(4); // will be "Second Line"

Obviously, this logic is amenable to being put into a separate method.

EDIT 3

If you need the elements of lyricLineInfo to be of type String[], it is vital that each element be a distinct array. Here are a few coding styles for adding elements:

ArrayList<String[]> lyricLineInfo = new ArrayList<String[]>();

String[] line = { "true", "true", "0.0", "5.0", "First Line" };
lyricLineInfo.add(line);
// now for a second style:
line = new String[5];
line[0] = "false";
line[1] = "false";
line[2] = "5.0";
line[3] = "10.0";
line[4] = "Second Line";
lyricLineInfo.add(line);
// and a third style:
lyricLineInfo.add(new String[] {
    "false", "true", "10.0", "15.0", "Third Line"
});

String secondLineTitle = lyricLineInfo.get(1)[4]; // will be "Second Line"