在 Java 中扩展多维数组 (2D)

发布于 2024-10-06 11:27:22 字数 110 浏览 5 评论 0原文

如何在 Java 中扩展多维数组？

我需要扩展它的第一个维度。它的格式如下：
myArray[x][7]

“7”在所有扩展部分上将保持“7”。

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温柔一刀 2024-10-13 11:27:22

Java 中的数组具有固定长度，因此您无法真正扩展它。您必须创建一个更大的新数组，然后将旧数组的内容复制到新数组中。像这样：

public class Test {

    public static void main(String[] args) {
        int[][] myArray = new int[3][7];

        // Print first dimension
        System.out.println(myArray.length);   // prints 3

        myArray = addRow(myArray);

        // Print first dimension
        System.out.println(myArray.length);   // prints 4

    }

    private static int[][] addRow(int[][] previous) {

        int prevRowCount = previous.length;

        int[][] withExtraRow = new int[prevRowCount + 1][];
        System.arraycopy(previous, 0, withExtraRow, 0, previous.length);
        withExtraRow[prevRowCount] = new int[] { 1, 2, 3, 4, 5, 6, 7 };

        return withExtraRow;
    }

}

您当然也可以使用动态增长的 ArrayList 等。（这实际上是处理动态增长数组时的首选方法。）

import java.util.*;

public class Test {

    public static void main(String[] args) {
        List<int[]> myArray = new ArrayList<int[]>();

        // Print first dimension
        System.out.println(myArray.size());   // prints 0

        // Add three rows
        myArray.add(new int[] {  1,  2,  3,  4,  5,  6,  7 });
        myArray.add(new int[] { 11, 12, 13, 14, 15, 16, 17 });
        myArray.add(new int[] { 21, 22, 23, 24, 25, 26, 27 });

        // Print first dimension
        System.out.println(myArray.size());   // prints 3

    }
}

Arrays in Java have fixed length, so you can't really extend it. You will have to create a new, larger, array, and then copy the content of the old array into the new one. Like this:

public class Test {

    public static void main(String[] args) {
        int[][] myArray = new int[3][7];

        // Print first dimension
        System.out.println(myArray.length);   // prints 3

        myArray = addRow(myArray);

        // Print first dimension
        System.out.println(myArray.length);   // prints 4

    }

    private static int[][] addRow(int[][] previous) {

        int prevRowCount = previous.length;

        int[][] withExtraRow = new int[prevRowCount + 1][];
        System.arraycopy(previous, 0, withExtraRow, 0, previous.length);
        withExtraRow[prevRowCount] = new int[] { 1, 2, 3, 4, 5, 6, 7 };

        return withExtraRow;
    }

}

You could of course also use for instance an ArrayList<SomeType[]> that grows dynamically. (This is actually the preferred way when dealing with dynamically growing arrays.)

import java.util.*;

public class Test {

    public static void main(String[] args) {
        List<int[]> myArray = new ArrayList<int[]>();

        // Print first dimension
        System.out.println(myArray.size());   // prints 0

        // Add three rows
        myArray.add(new int[] {  1,  2,  3,  4,  5,  6,  7 });
        myArray.add(new int[] { 11, 12, 13, 14, 15, 16, 17 });
        myArray.add(new int[] { 21, 22, 23, 24, 25, 26, 27 });

        // Print first dimension
        System.out.println(myArray.size());   // prints 3

    }
}

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花心好男孩 2024-10-13 11:27:22

您还可以使用 Arrays.copyOf 方法，例如：

import java.util.Arrays;

public class Array2D {
    public static void main(String[] args) {
        int x = 5 //For example
        int[][] myArray = [x][7];

        myArray = Arrays.copyOf(myArray, myArray.length + 1); //Extending for one
        myArray[myArray.length - 1] = new int[]{1, 2, 3, 4, 5, 6, 7};
    }
}

You could also use Arrays.copyOf method, for example:

import java.util.Arrays;

public class Array2D {
    public static void main(String[] args) {
        int x = 5 //For example
        int[][] myArray = [x][7];

        myArray = Arrays.copyOf(myArray, myArray.length + 1); //Extending for one
        myArray[myArray.length - 1] = new int[]{1, 2, 3, 4, 5, 6, 7};
    }
}

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