Arrays.fill 用 Ja​​va 中的多维数组

问题描述

如何在不使用循环的情况下在 Java 中填充多维数组?我试过了:

How can I fill a multidimensional array in Java without using a loop? I've tried:

double[][] arr = new double[20][4];
Arrays.fill(arr, 0);

这导致 java.lang.ArrayStoreException: java.lang.Double

推荐答案

这是因为 double[][] 是一个 double[] 的数组，你可以'不要将 0.0 分配给(这就像执行 double[] vector = 0.0).事实上，Java 没有真正的多维数组.

This is because a double[][] is an array of double[] which you can't assign 0.0 to (it would be like doing double[] vector = 0.0). In fact, Java has no true multidimensional arrays.

碰巧的是，0.0 是 Java 中 doubles 的默认值，因此当您从 new 获取矩阵时，该矩阵实际上已经填充了零.但是，如果您想用 1.0 填充它，您可以执行以下操作:

As it happens, 0.0 is the default value for doubles in Java, thus the matrix will actually already be filled with zeros when you get it from new. However, if you wanted to fill it with, say, 1.0 you could do the following:

我不认为 API 提供了一种无需循环即可解决此问题的方法.然而，使用 for-each 循环来完成它很简单.

I don't believe the API provides a method to solve this without using a loop. It's simple enough however to do it with a for-each loop.

double[][] matrix = new double[20][4];

// Fill each row with 1.0
for (double[] row: matrix)
    Arrays.fill(row, 1.0);

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