我一直在尝试在 java 中附加两个二维数组。是否可以举个例子，因为我一直在尝试查找但找不到。
int [][]appendArray(empty,window)
{
int [][]result= new int [empty.length][empty[0].length+window[0].length];
}
【问题讨论】：
单线带流
int[][] combi = Stream.concat( Arrays.stream( a ), Arrays.stream( b ) ).toArray( int[][]::new );
二维Object数组here的对应题
【讨论】：
如果我理解正确，您想在与 DomS 和 MeBigFatGuy 所想的相反的维度上附加它。如果我是正确的，有两种方法：
如果“列”高度（二维的长度）在每个数组中是固定的，则可以使用此方法。如果数组的第一维长度不同，它会留下空白（零填充）单元格。为了让这段代码更安全，你可能想要
/**
* For fixed "column" height. "Blank cells" will be left, if the two arrays have different "width"
*/
static int[][] appendArray2dFix(int[][] array1, int[][] array2){
int a = array1[0].length, b = array2[0].length;
int[][] result = new int[Math.max(array1.length,array2.length)][a+b];
//append the rows, where both arrays have information
int i;
for (i = 0; i < array1.length && i < array2.length; i++) {
if(array1[i].length != a || array2[i].length != b){
throw new IllegalArgumentException("Column height doesn't match at index: " + i);
}
System.arraycopy(array1[i], 0, result[i], 0, a);
System.arraycopy(array2[i], 0, result[i], a, b);
}
//Fill out the rest
//only one of the following loops will actually run.
for (; i < array1.length; i++) {
if(array1[i].length != a){
throw new IllegalArgumentException("Column height doesn't match at index: " + i);
}
System.arraycopy(array1[i], 0, result[i], 0, a);
}
for (; i < array2.length; i++) {
if(array2[i].length != b){
throw new IllegalArgumentException("Column height doesn't match at index: " + i);
}
System.arraycopy(array2[i], 0, result[i], a, b);
}
return result;
}
如果您希望允许每个数组中的列不同，这是可能的，只需稍作更改。这不会留下任何空单元格。
/**
* For variable "column" height. No "blank cells"
*/
static int[][] appendArray2dVar(int[][] array1, int[][] array2){
int[][] result = new int[Math.max(array1.length,array2.length)][];
//append the rows, where both arrays have information
int i;
for (i = 0; i < array1.length && i < array2.length; i++) {
result[i] = new int[array1[i].length+array2[i].length];
System.arraycopy(array1[i], 0, result[i], 0, array1[i].length);
System.arraycopy(array2[i], 0, result[i], array1[i].length, array2[i].length);
}
//Fill out the rest
//only one of the following loops will actually run.
for (; i < array1.length; i++) {
result[i] = new int[array1[i].length];
System.arraycopy(array1[i], 0, result[i], 0, array1[i].length);
}
for (; i < array2.length; i++) {
result[i] = new int[array2[i].length];
System.arraycopy(array2[i], 0, result[i], 0, array2[i].length);
}
return result;
}
从 DomS 修改的测试代码
public static void main(String[] args) {
//Test Var
int[][] array1 = new int[][] {
{1, 2, 3},
{3, 4, 5, 6},
};
int[][] array2 = new int[][] {
{11, 12, 13,14 },
{13, 14, 15, 16, 17},
};
int[][] expected = new int[][] {
{1, 2, 3, 11, 12, 13, 14},
{3, 4, 5, 6, 13, 14, 15, 16, 17}
};
int[][] appended = appendArray2dVar(array1, array2);
System.out.println("This");
for (int i = 0; i < appended.length; i++) {
for (int j = 0; j < appended[i].length; j++) {
System.out.print(appended[i][j]+", ");
}
System.out.println();
}
System.out.println("Should be the same as this");
for (int i = 0; i < expected.length; i++) {
for (int j = 0; j < expected[i].length; j++) {
System.out.print(expected[i][j]+", ");
}
System.out.println();
}
//Test Fix
array1 = new int[][] {
{1, 2, 3, 4},
{3, 4, 5, 6},
};
array2 = new int[][] {
{11, 12, 13},
{13, 14, 15},
};
expected = new int[][] {
{1, 2, 3, 4,11, 12, 13},
{3, 4, 5, 6, 13, 14, 15}
};
appended = appendArray2dFix(array1, array2);
System.out.println("This");
for (int i = 0; i < appended.length; i++) {
for (int j = 0; j < appended[i].length; j++) {
System.out.print(appended[i][j]+", ");
}
System.out.println();
}
System.out.println("Should be the same as this");
for (int i = 0; i < expected.length; i++) {
for (int j = 0; j < expected[i].length; j++) {
System.out.print(expected[i][j]+", ");
}
System.out.println();
}
}
【讨论】：
给你：
import java.util.Arrays;
public class Array2DAppend {
public static void main(String[] args) {
int[][] a = new int[][] {{1, 2}, {3, 4}};
int[][] b = new int[][] {{1, 2, 3}, {3, 4, 5}};
System.out.println(Arrays.deepToString(a));
System.out.println(Arrays.deepToString(b));
System.out.println(Arrays.deepToString(append(a, b)));
}
public static int[][] append(int[][] a, int[][] b) {
int[][] result = new int[a.length + b.length][];
System.arraycopy(a, 0, result, 0, a.length);
System.arraycopy(b, 0, result, a.length, b.length);
return result;
}
}
和输出：
[[1, 2], [3, 4]]
[[1, 2, 3], [3, 4, 5]]
[[1, 2], [3, 4], [1, 2, 3], [3, 4, 5]]
【讨论】：
如果我正确理解了您的问题，此方法会将两个二维数组附加在一起 -
private static int[][] appendArrays(int[][] array1, int[][] array2) {
int[][] ret = new int[array1.length + array2.length][];
int i = 0;
for (;i<array1.length;i++) {
ret[i] = array1[i];
}
for (int j = 0;j<array2.length;j++) {
ret[i++] = array2[j];
}
return ret;
}
这个快速的代码将测试它 -
int[][] array1 = new int[][] {
{1, 2, 3},
{3, 4, 5, 6},
};
int[][] array2 = new int[][] {
{11, 12, 13},
{13, 14, 15, 16},
};
int[][] expected = new int[][] {
{1, 2, 3},
{3, 4, 5, 6},
{11, 12, 13},
{13, 14, 15, 16},
};
int[][] appended = appendArrays(array1, array2);
System.out.println("This");
for (int i = 0; i < appended.length; i++) {
for (int j = 0; j < appended[i].length; j++) {
System.out.print(appended[i][j]+", ");
}
System.out.println();
}
System.out.println("Should be the same as this");
for (int i = 0; i < expected.length; i++) {
for (int j = 0; j < expected[i].length; j++) {
System.out.print(expected[i][j]+", ");
}
System.out.println();
}
【讨论】：
我猜“附加”是指用另一个矩阵的行来扩展矩阵的行数？在这种情况下，两个数组/矩阵必须有相同的列数！ 因此，例如，您可以将 a[7][6] 与 b[100][6] 附加，这将通过简单地将 b 的 100 行附加到 a 的 7 行来生成数组 c[107][6] ——但这仅仅是因为它们两者都有 6 列。例如，将 a[7][3] 附加到 b[100][6] 是没有意义的！ 所以你的功能必须预先强制执行这些。 不，如果不编写自己的代码，Java 就无法做到这一点：
int[][] appendArray( empty, window ) {
if( empty[0].length != window[0].length ) throw new IllegalArgumentException( "Wrong column size" );
int[][] result = new int[empty.length + window.length];
for( int i = 0; i < empty.length; i++ )
System.arrayCopy( empty[i], 0, result[0], 0, empty[i].length );
for( int i = 0; i < window.length; i++ )
System.arrayCopy( window[i], 0, result[i + empty.length], 0, window[i].length );
return result;
}
【讨论】：