It is said that memory is single-dimensional, then how multi-dimensional arrays are represented (and manipulated) in memory. Please reply if anyone knows
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It is said that memory is single-dimensional, then how multi-dimensional arrays are represented (and manipulated) in memory. Please reply if anyone knows
They say a picture says more than a thousand words, so here goes: given the following two dimensional array:Quote:
Originally Posted by Riaz Ali
... the jvm builds it up as a bunch of one dimensional arrays:Code:int[][] array= new int[3][4];
As you can see the two dimensional array is just a bunch of one dimensional arrays held together by a so called 'dope vector' (the vertical array on the left). Each slot of that dope vector points to a row of the original array.Code:+---+
| | +---+---+---+---+
| ---> | | | | |
| | +---+---+---+---+
+---+
| | +---+---+---+---+
| ---> | | | | |
| | +---+---+---+---+
+---+
| | +---+---+---+---+
| ---> | | | | |
| | +---+---+---+---+
+---+
kind regards,
Jos
Otherwise known as an array of arrays. The actual array variable is a handle to an array of other array handles, which are either handles to arrays of the objects or more array handles, and so on...
Which means this is valid :)
Edit: can't create a 2D array like that using the simple Type[][] array = new Type[xSize][ySize] though. You'd need a for loop to do that.Code:+---+
| | +---+---+---+---+
| ---> | | | | |
| | +---+---+---+---+
+---+
| | +---+---+---+
| ---> | | | |
| | +---+---+---+
+---+
| | +---+---+---+---+
| ---> | | | | |
| | +---+---+---+---+
+---+
Not necessarily. There could just as well be individual assignment statements.Quote:
Originally Posted by Singing Boyo
db
Even a single initialization of the ragged array/matrix can do it:Quote:
Originally Posted by Darryl.Burke
kind regards,Code:int[][] array= { {1, 2, 3, 4}, {5, 6, 7}, {8, 9, 10 11}};
Jos
edit: if you know that sizes and values of the individual arrays at compile time that is ...