Initialising a multidimensional array in Java

Question

What is the correct way to declare a multidimensional array and assign values to it   This is what I have   int x   5  int y   5   String     myStringArray   new String  x  y    myStringArray 0  x     a string   myStringArray 0  y     another string

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int     myNums      1  2  3  4  5  6  7    5  6  7  8  9  10  11      for  int x   0  x  lt  myNums length    x        for int y   0  y  lt  myNums i  length    y           System out print myNums x  y               Output  1 2 3 4 5 6 7 5 6 7 8 9 10 11

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Try replacing the appropriate lines with   myStringArray 0  x-1     a string   myStringArray 0  y-1     another string     Your code is incorrect because the sub-arrays have a length of y  and indexing starts at 0  So setting to myStringArray 0  y  or myStringArray 0  x  will fail because the indices x and y are out of bounds   String     myStringArray   new String  x  y   is the correct way to initialise a rectangular multidimensional array  If you want it to be jagged  each sub-array potentially has a different length  then you can use code similar to this answer  Note however that John s assertion that you have to create the sub-arrays manually is incorrect in the case where you want a perfectly rectangular multidimensional array

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I ll add that if you want to read the dimensions  you can do this   int       a   new int 4  3  2    System out println a length       4 System out println a 0  length      3 System out println a 0  0  length     2   You can also have jagged arrays  where different rows have different lengths  so a 0  length    a 1  length

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Multidimensional Array in Java Returning a multidimensional array Java does not truely support multidimensional arrays  In Java  a two-dimensional array is simply an array of arrays  a three-dimensional array is an array of arrays of arrays  a four-dimensional array is an array of arrays of arrays of arrays  and so on    We can define a two-dimensional array as   int    num        1 2    1 2    1 2    1 2    int       num   new int 4  2  num 0  0    1  num 0  1    2  num 1  0    1  num 1  1    2  num 2  0    1  num 2  1    2  num 3  0    1  num 3  1    2   If you don t allocate  let s say num 2  1   it is not initialized and then it is automatically allocated 0  that is  automatically num 2  1    0   Below  num1 length gives you rows   While num1 0  length gives you the number of elements related to num1 0   Here num1 0  has related arrays num1 0  0  and num 0  1  only   Here we used a for loop which helps us to calculate num1 i  length  Here i is incremented through a loop  class array       static int     add int     num1 int     num2                int     temp   new int num1 length  num1 0  length           for int i   0  i lt temp length  i                          for int j   0  j lt temp i  length  j                                  temp i  j    num1 i  j  num2 i  j                                   return temp             public static void main String args                     We can define a two-dimensional array as              1   int   num       1 2   1 2   1 2   1 2                2   int     num   new int 4  2                   num 0  0    1                   num 0  1    2                   num 1  0    1                   num 1  1    2                   num 2  0    1                   num 2  1    2                   num 3  0    1                   num 3  1    2                    If you don t allocate let s say num 2  1  is                  not initialized  and then it is automatically                  allocated 0  that is  automatically num 2  1    0                3  Below num1 length gives you rows               4  While num1 0  length gives you number of elements                  related to num1 0   Here num1 0  has related arrays                  num1 0  0  and num 0  1  only                5  Here we used a  for  loop which helps us to calculate                  num1 i  length  and here i is incremented through a loop                     int num1         1 2   1 2   1 2   1 2            int num2         1 2   1 2   1 2   1 2             int num3       add num1 num2           for int i   0  i lt num1 length  i                          for int j   0  j lt num1 j  length  j                    System out println  quot num3  quot    i    quot    quot    j    quot    quot    num3 i  j

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You can declare multi dimensional arrays like       4 x 5 String arrays  all Strings are null     0  - gt   null null null null null      1  - gt   null null null null null      2  - gt   null null null null null      3  - gt   null null null null null   String     sa1   new String 4  5   for int i   0  i  lt  sa1 length  i                   sa1 length    4     for  int j   0  j  lt  sa1 i  length  j            sa1 i  length    5         sa1 i  j     new String value                5 x 0  All String arrays are null     null      null      null      null      null  String     sa2   new String 5     for int i   0  i  lt  sa2 length  i          String   anon   new String     your number here             or String   anon   new String    I m    a    new    array        sa2 i    anon         0  - gt    I m   in   the    0th    array       1  - gt    I m    in    another   String     sa3   new String        I m   in   the    0th    array     I m    in    another

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You can also use the following construct   String     myStringArray   new String           X0    Y0                                                    X1    Y1                                                    X2    Y2                                                    X3    Y3                                                    X4    Y4

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Java doesn t have  true  multidimensional arrays   For example  arr i  j  k  is equivalent to   arr i   j   k   In other words  arr is simply an array  of arrays  of arrays   So  if you know how arrays work  you know how multidimensional arrays work     Declaration   int       threeDimArr   new int 4  5  6     or  with initialization   int       threeDimArr         1  2      3  4          5  6      7  8            Access   int x   threeDimArr 1  0  1     or  int     row   threeDimArr 1       String representation   Arrays deepToString threeDimArr     yields      1  2    3  4      5  6    7  8       Useful articles   Java  Initializing a multidimensional array Java  Matrices and Multidimensional Arrays

[java] Initialising a multidimensional array in Java

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