I have unknown number of records and I need to put all that records in string two dimensional array.
I don't know the number of records and due to this, don't know number of rows and columns which is required for string 2d array initialization.
Currently I am using as below:
String[][] data = new String[100][100];
Here I hard coded number of rows and columns but need something dynamic size allowable in string 2d array. Any suggestion pls!
Rgrds
You can use the following class which stores your data in a HashMap and is able to convert it to a two dimensional string array.
public class ArrayStructure {
private HashMap<Point, String> map = new HashMap<Point, String>();
private int maxRow = 0;
private int maxColumn = 0;
public ArrayStructure() {
}
public void add(int row, int column, String string) {
map.put(new Point(row, column), string);
maxRow = Math.max(row, maxRow);
maxColumn = Math.max(column, maxColumn);
}
public String[][] toArray() {
String[][] result = new String[maxRow + 1][maxColumn + 1];
for (int row = 0; row <= maxRow; ++row)
for (int column = 0; column <= maxColumn; ++column) {
Point p = new Point(row, column);
result[row][column] = map.containsKey(p) ? map.get(p) : "";
}
return result;
}
}
Example code
public static void main(String[] args) throws IOException {
ArrayStructure s = new ArrayStructure();
s.add(0, 0, "1");
s.add(1, 1, "4");
String[][] data = s.toArray();
for (int i = 0; i < data.length; ++i) {
for (int j = 0; j < data[i].length; ++j)
System.out.print(data[i][j] + " ");
System.out.println();
}
}
Output
1
4
You can simply initialize with a literal, empty two-dimensional array:
String[][] data = new String[][]{{}}
Map<String, List<String>> instead, it'll let you use real dynamic sizing.You can temporarely store them in a List<String[]> and use List#toArray(String[]) to convert it to a two dimensional array.
Example
public static void main(String[] args) throws IOException {
BufferedReader r = new BufferedReader(new FileReader(new File(
"data.txt")));
String line;
List<String[]> list = new ArrayList<String[]>();
while ((line = r.readLine()) != null)
list.add(line.split(" +"));
String[][] data = new String[list.size()][];
list.toArray(data);
for (int i = 0; i < data.length; ++i) {
for (int j = 0; j < data[i].length; ++j)
System.out.print(data[i][j]+" ");
System.out.println();
}
r.close();
}
Data.txt
1 2 3 4 5
2 5 3
2 5 5 8
Output
1 2 3 4 5
2 5 3
2 5 5 8
This should work:
public static void main(String args[]) throws IOException {
// create the object
String[][] data;
// ----- dinamically know the matrix dimension ----- //
BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(System.in));
int r = Integer.parseInt(bufferedReader.readLine());
int c = Integer.parseInt(bufferedReader.readLine());
// ------------------------------------------------ //
// allocate the object
data = new String[r][c];
// init the object
for (int i = 0; i < r; i++)
for (int j = 0; j < c; j++)
data[i][j] = "hello";
}
In this example you know the matrix dimension runtime, specifying it manually via the console.
