在Java中，如何从大于1D的数组中获取长度值？

Question

In java, what would myArray.length be referencing in a 2D array? Eg

double[][] myArray = new double[3][5];

say you want to run a couple of for-loops over the array without putting the rows and columns in an argument to get hold of their value, is there a neat way to do this?

Answer 1

Use myArray.length and myArray[0].length . (This assumes that all of your "sub"-arrays are the same length.)

Answer 2

In java, what would myArray.length be referencing in a 2D array?

A 2 dimensional array of double is a 1-dimensional array or 1 dimensional array of double. myArray[0] is a an array of double ( double[] ), as is myArray[1]

So myArray.length is the number of arrays.

say you want to run a couple of for-loops over the array without putting the rows and columns in an argument to get hold of their value, is there a neat way to do this?

You mean you want to access myArray[2][3] without using 3 and 4 ? There isn't a way to do this in Java

Answer 3

As of Java 5 you can use a different looping construct, " for each ", where you avoid using array indices;

class Test {
  public static void main( String[] args ) {

    int[][] myArray = new int[][] { { 1, 2, 3 }, { 4, 5, 6 } };

    for ( int[] outer : myArray ) {
      for ( int inner : outer ) {
        System.out.println( inner );
      }
    }
  }
}

This prints;

$ java Test
1
2
3
4
5
6