Double array initialization in Java

Question

I was reading a book on Java and came across an example in which an array of type double was initialized in a way that I haven t seen before  What type of initialization is it and where else can it be used   double m            0 0 1 0 2 0 3 0        0 1 1 1 2 1 3 1        0 2 1 2 2 2 3 2        0 3 1 3 2 3 3 3

User · Answer

It is called an array initializer and can be explained in the Java specification 10.6.

This can be used to initialize any array, but it can only be used for initialization (not assignment to an existing array). One of the unique things about it is that the dimensions of the array can be determined from the initializer. Other methods of creating an array require you to manually insert the number. In many cases, this helps minimize trivial errors which occur when a programmer modifies the initializer and fails to update the dimensions.

Basically, the initializer allocates a correctly sized array, then goes from left to right evaluating each element in the list. The specification also states that if the element type is an array (such as it is for your case... we have an array of double[]), that each element may, itself be an initializer list, which is why you see one outer set of braces, and each line has inner braces.

User · Answer

double m     declares an array of arrays  so called multidimensional array   m 0  points to an array in the size of four  containing 0 0 1 0 2 0 3 0  Simple math shows the values are actually 0 0 0 0   Second line is also array in the size of four  containing 0 1 2 3   And so on     I guess this mutiple format in you book was to show that 0 0 is row 0 column 0  0 1 is row 0 column 1  and so on

User · Answer

If you can accept Double Objects than this post is helpful  Initialization of an ArrayList in one line  List lt Double gt  y   Arrays asList null  1 0  2 0   Double x   y get 1

User · Answer

This is array initializer syntax  and it can only be used on the right-hand-side when declaring a variable of array type  Example   int   x    1 2 3 4   String y     a   b   c      If you re not on the RHS of a variable declaration  use an array constructor instead   int   x  x   new int   1 2 3 4   String y  y   new String    a   b   c      These declarations have the exact same effect  a new array is allocated and constructed with the specified contents   In your case  it might actually be clearer  less repetitive  but a bit less concise  to specify the table programmatically   double     m   new double 4  4    for int i 0  i lt 4  i          for int j 0  j lt 4  j              m i  j    i j

User · Answer

You can initialize an array by writing actual values it holds in curly braces on the right hand side like   String   strArr      one    two    three    int   numArr     1  2  3     In the same manner two-dimensional array or array-of-arrays holds an array as a value  so   String strArrayOfArrays       a    b    c      one    two    three        Your example shows exactly that  double m              0 0 1 0 2 0 3 0        0 1 1 1 2 1 3 1        0 2 1 2 2 2 3 2        0 3 1 3 2 3 3 3       But also the multiplication of number will also be performed and its the same as   double m          0  0  0  0    0  1  2  3    0  2  4  6    0  3  6  9

[java] Double array initialization in Java

Examples related to java

Examples related to arrays

Examples related to initialization

Examples related to double