java中二维数组的增强for循环
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Enhanced for loop for 2d array in java
提问by Devraj Jaiman
int Site[][] = new int[N][N];
for(int[] i : Site)
for(int j:i)
Site[i][j]=1;
This code is showing some error. Please correct the code.
此代码显示一些错误。请更正代码。
回答by Patricia Shanahan
int Site[][] = new int[N][N];
for (int[] i : Site)
for (int j : i)
i[j] = 1;
The elements of Site are of type int[], so that has to be the type of the first index variable, i. That gives you a reference to an int[], so index into that to access the individual element.
Site 的元素是 int[] 类型，因此它必须是第一个索引变量的类型，即。这为您提供了对 int[] 的引用，因此可以对其进行索引以访问单个元素。
The code could be made clearer by the use of a more meaningful identifier for the out loop index:
通过为循环索引使用更有意义的标识符，可以使代码更清晰：
int Site[][] = new int[N][N];
for (int[] siteRow : Site)
for (int i : siteRow)
siteRow[i] = 1;
回答by Mateusz
If you want to use for(int[] i : Site)and for(int j:i), you should refer to the element as j = 1, not Site[i][j]=1;because i's type is int[]and jtakes values of its elements.
如果您想使用for(int[] i : Site)and for(int j:i)，您应该将元素称为j = 1，而不是Site[i][j]=1;因为i的类型是int[]并且j采用其元素的值。
回答by jason
You can not use a for-each loop to modify the values stored in the array. Use a regular for loop for that.
您不能使用 for-each 循环来修改存储在数组中的值。为此使用常规 for 循环。
回答by SpicyWeenie
I use this to print the positions of each element of a 2D array with an enhanced for-loop:
我使用它来打印具有增强的 for 循环的 2D 数组的每个元素的位置：
int[][] grid = new int[3][3];
String divider = "------------------";
int y = 0;
for (int[] row : grid)
{
for (int dividers : row)
System.out.print(divider);
System.out.println();
int x = 0;
for (int columns : row)
{
row[columns] = y;
System.out.print("| (row: " + row[columns] + " col: " + x + ") ");
x++;
}
y++;
System.out.println("| ");
}
for (int[] lastDivider : grid)
System.out.print(divider);
回答by tilak
In your problem using the previous solution we come across another problem like,
在您使用先前解决方案的问题中，我们遇到了另一个问题，例如，
0 1 1
0 1 1
0 1 1
0 1 1
0 1 1
0 1 1
That is first element of the array gets zero every time we print the value of elements. Now, the solution that will resolve your problem is to use the control statements like,
也就是说，每次我们打印元素的值时，数组的第一个元素都会变为零。现在，解决您的问题的解决方案是使用控制语句，例如，
for(int[] row: B)
{
for(int j: row)
{
if(j==0)
System.out.print(" "+row[j]);
else
System.out.print(" "+j);
}
System.out.println();
}
This will definitely solve the problem of first element being ZERO.
这肯定会解决第一个元素为零的问题。
回答by Andrew
int[][] twodim = new int[4][3];
for (int[] row : twodim) {
for (int j = 0; j < row.length; j++) {
row[j] = 1;
}
}
for (int[] row : twodim) {
for (int j : row) {
System.out.println(row[j]);
}
}
