I want to create a two dimensional array dynamically.
I know the number of columns. But the number of rows are being changed dynamically. I tried the array list, but it stores the value in single dimension only. What can I do?
This question is related to
java
multidimensional-array
One more example for 2 dimension String array:
public void arrayExam() {
List<String[]> A = new ArrayList<String[]>();
A.add(new String[] {"Jack","good"});
A.add(new String[] {"Mary","better"});
A.add(new String[] {"Kate","best"});
for (String[] row : A) {
Log.i(TAG,row[0] + "->" + row[1]);
}
}
Output:
17467 08-02 19:24:40.518 8456 8456 I MyExam : Jack->good
17468 08-02 19:24:40.518 8456 8456 I MyExam : Mary->better
17469 08-02 19:24:40.518 8456 8456 I MyExam : Kate->best
simple you want to inialize a 2d array and assign a size of array then a example is
public static void main(String args[])
{
char arr[][]; //arr is 2d array name
arr = new char[3][3];
}
//this is a way to inialize a 2d array in java....
There are no multi-dimensional arrays in Java, there are, however, arrays of arrays.
Just make an array of however large you want, then for each element make another array however large you want that one to be.
int array[][];
array = new int[10][];
array[0] = new int[9];
array[1] = new int[8];
array[2] = new int[7];
array[3] = new int[6];
array[4] = new int[5];
array[5] = new int[4];
array[6] = new int[3];
array[7] = new int[2];
array[8] = new int[1];
array[9] = new int[0];
Alternatively:
List<Integer>[] array;
array = new List<Integer>[10];
// of you can do "new ArrayList<Integer>(the desired size);" for all of the following
array[0] = new ArrayList<Integer>();
array[1] = new ArrayList<Integer>();
array[2] = new ArrayList<Integer>();
array[3] = new ArrayList<Integer>();
array[4] = new ArrayList<Integer>();
array[5] = new ArrayList<Integer>();
array[6] = new ArrayList<Integer>();
array[7] = new ArrayList<Integer>();
array[8] = new ArrayList<Integer>();
array[9] = new ArrayList<Integer>();
How about making a custom class containing an array, and use the array of your custom class.
Scanner sc=new Scanner(System.in) ;
int p[][] = new int[n][] ;
for(int i=0 ; i<n ; i++)
{
int m = sc.nextInt() ; //Taking input from user in JAVA.
p[i]=new int[m] ; //Allocating memory block of 'm' int size block.
for(int j=0 ; j<m ; j++)
{
p[i][j]=sc.nextInt(); //Initializing 2D array block.
}
}
List<Integer>[] array;
array = new List<Integer>[10];
this the second case in @TofuBeer's answer is incorrect. because can't create arrays with generics. u can use:
List<List<Integer>> array = new ArrayList<>();
Here is a simple example.
this method will return a 2 dimensional tType
array
public tType[][] allocate(Class<tType> c,int row,int column){
tType [][] matrix = (tType[][]) Array.newInstance(c,row);
for (int i = 0; i < column; i++) {
matrix[i] = (tType[]) Array.newInstance(c,column);
}
return matrix;
}
say you want a 2 dimensional String array, then call this function as
String [][] stringArray = allocate(String.class,3,3);
This will give you a two dimensional String array with 3 rows and 3 columns;
Note that in Class<tType> c
-> c
cannot be primitive type like say, int
or char
or double
. It must be non-primitive like, String
or Double
or Integer
and so on.
Try to make Treemap < Integer, Treemap<Integer, obj> >
In java, Treemap is sorted map. And the number of item in row and col wont screw the 2D-index you want to set. Then you can get a col-row table like structure.
Source: Stackoverflow.com