多维数组[] [] VS [，] [英] Multidimensional Array [][] vs [,]

问题描述

double[][] ServicePoint = new double[10][9]; // <-- gives an error (1)
double[,] ServicePoint = new double[10,9]; // <-- ok (2)

有什么自己的区别？的（1）的产生错误，是什么原因？

What's their difference? (1) yields an error, what's the reason?

和

double d = new double[9]
ServicePoint[0] = d;

使用的（2）的会提示错误。为什么呢？

using (2) will prompt an error. Why?

推荐答案

一个是一个数组的数组，一个是一个二维数组。前者可以是锯齿状，后者是均匀的。

One is an array of arrays, and one is a 2d array. The former can be jagged, the latter is uniform.

这是一个双击[] [] 可有效地是：

double[][] x = new double[5][];

x[0] = new double[10];
x[1] = new double[5];
x[2] = new double[3];
x[3] = new double[100];
x[4] = new double[1];

由于阵列中的每个条目是的数组的引用双。随着交错数组，你可以做一个分配给数组像你想在你的第二个例子：

Because each entry in the array is a reference to an array of double. With a jagged array, you can do an assignment to an array like you want in your second example:

x[0] = new double[13];

在第二项，因为它是一个统一的二维数组，你不能分配一维数组的行或列，因为你必须索引的行和列两者，它可以让你到一个单一的双击：

On the second item, because it is a uniform 2d array, you can't assign a 1d array to a row or column, because you must index both the row and column, which gets you down to a single double:

double[,] ServicePoint = new double[10,9];

ServicePoint[0]... // <-- meaningless, a 2d array can't use just one index.

更新

要阐明根据你的问题，你的＃1有一个语法错误的原因是因为你有这样的：

To clarify based on your question, the reason your #1 had a syntax error is because you had this:

double[][] ServicePoint = new double[10][9];

和您不能指定在施工时第二个索引。关键是，的ServicePoint是的不的二维数组，但一维数组（阵列），因此，因为要创建一维数组（阵列），您只需指定一个索引：

And you can't specify the second index at the time of construction. The key is that ServicePoint is not a 2d array, but an 1d array (of arrays) and thus since you are creating a 1d array (of arrays), you specify only one index:

double[][] ServicePoint = new double[10][];

然后，当您在阵列中创建的每一个项目，每一个这些也都是数组，这样的然后的您可以指定他们的尺寸（可以是不同的，因此，长期的锯齿状数​​组）：

Then, when you create each item in the array, each of those are also arrays, so then you can specify their dimensions (which can be different, hence the term jagged array):

ServicePoint[0] = new double[13];
ServicePoint[1] = new double[20];

希望帮助！

这篇关于多维数组[] [] VS [，]的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！