以下是正在进行的基本代码。我已经提示输入行数和列数，这是有效的。问题是一旦程序到达"Enter the data..."它打印它，但完全忽略了对Matrix的调用。在Matrix内部，我也提示使用扫描仪类输入矩阵。此外，我意识到目前还没有结束。请帮忙。
case 1:
System.out.println("Enter the data for the first matrix.");
//input needed
MatrixOne = Matrix(Rows, Columns);
System.out.println("+");
System.out.println("Enter the data for the second matrix.");
MatrixTwo = Matrix(Rows, Columns);
int[][]Plus = Add(MatrixOne, MatrixTwo, Rows, Columns);
Print(Rows, Columns, Plus);
break;
以下是方法：
public static int [][] Matrix(int Rows, int Columns)
{
int[][] NewMatrix = new int[Rows][Columns];
for(int i=0; i<Rows; i++)
{
for(int j=0; j<Columns; j++)
{
System.out.println("HIIIIIIII");
NewMatrix[i][j] = keyboard.nextInt ();
}
}
return NewMatrix;
}
目前是输出：
Please choose an operation: Addition(1) or Subtract(2)1
How many Rows would you like your matrix to have?
2
How many Columns would you like your matrix to have?
2
Enter the data for the first matrix.
+
Enter the data for the second matrix.
=
Please choose an operation: Addition(1) or Subtract(2)
这就是所有内容：
int Rows=0;
int Columns=0;
int [][] MatrixOne;
int [][] MatrixTwo;
do{
System.out.print("Please choose an operation: Addition(1) or Subtract(2)");
operation = keyboard.nextInt();
RowColumns(Rows, Columns);
这是方法：
public static void RowColumns(int Rows, int Columns)
{
Scanner keyboard = new Scanner(System.in);
System.out.println("How many Rows would you like your matrix to have?");
Rows = keyboard.nextInt();
System.out.println("How many Columns would you like your matrix to have?");
Columns = keyboard.nextInt();
}
main：
public static void main(String[] args)
{
String End;
int operation;
int Rows = 0;
int Columns = 0;
int [][] MatrixOne;
int [][] MatrixTwo;
do{
System.out.print("Please choose an operation: Addition(1) or Subtract(2)");
operation = keyboard.nextInt();
RowColumns(Rows, Columns);
/////////////////READS INPUT AND DETERMINES TO ADD OR SUBTRACT//////////////////////////////////
switch(operation)//Reads the value of the variable Operation. If Operation equals 1, the program will add the matrices,...
//if Operation equals 2, the program will subtract the matrices, and if the Operation equals anything other than 1 or 2, the...
//user will be prompted to enter either 1 or 2 again.
{
case 1:
System.out.println("Enter the data for the first matrix.");
//input needed
MatrixOne = Matrix(Rows, Columns);
System.out.println("+");
System.out.println("Enter the data for the second matrix.");
MatrixTwo = Matrix(Rows, Columns);
int[][]Plus = Add(MatrixOne, MatrixTwo, Rows, Columns);
Print(Rows, Columns, Plus);
break;
case 2:
System.out.println("Enter the data for the first matrix.");
MatrixOne = Matrix(Rows, Columns);
System.out.println("-");
System.out.println("Enter the data for the second matrix.");
MatrixTwo = Matrix(Rows, Columns);
int[][]Minus = Subtract(MatrixOne,MatrixTwo, Rows, Columns);
Print(Rows, Columns, Minus);
break;
default: System.out.println("Please enter 1 to add the matrices or 2 to subtract them.");
}//End of Switch
}while(operation != 1 || operation != 2);
}//End of main
答案 0 :(得分：1)
Java是pass by value。
在RowColumns函数中，您是passing两个整数by value，这意味着只有它们的值传递给函数，而不是引用。因此，这些变量的实际引用不会受到影响。因此，在RowColumns(Rows, Columns)调用后，Rows和Columns变量将与其初始值（0,0）保持一致。
如果要更改函数内部变量的值，则应返回它们。
为此，您可以为这两个值定义容器：
public class Size {
public int Rows;
public int Columns;
}
然后您可以初始化并将其用作;
public static void Main(String[] args) {
...
Size size = new Size();
...
size = RowColumns(size);
...
}
public Size RowColumns(Size size)
{
Scanner keyboard = new Scanner(System.in);
System.out.println("How many Rows would you like your matrix to have?");
size.Rows = keyboard.nextInt();
System.out.println("How many Columns would you like your matrix to have?");
size.Columns = keyboard.nextInt();
return size;
}
答案 1 :(得分：0)
在Matrix方法中，如果行或列为零，则不会进入循环;所以也许它们的值可能为零。
答案 2 :(得分：0)
您的代码实际上完全正在调用Matrix方法，问题在于您的RowColumns方法。您的RowColumns方法实际上并未设置您认为的变量，因此当调用Matrix方法时，传递给它的行和列变量为零。
让我分解究竟发生了什么。在java中，整数按值传递，而不是通过引用传递。这意味着，当您调用RowColumns(Row, Columns);时，实际发生的是行和列的实际值，并将其发送到RowColumns方法，而不是变量本身。实际上这种情况正在发生RowColumns(0, 0);
尽管RowColumns方法中的参数具有相同的名称，但它们不是同一个变量。这是另一种查看代码的方法。
int Rows1=0;
int Columns1=0;
RowColumns(Rows1, Columns1);
和您的RowColumns方法
public static void RowColumns(int Rows2, int Columns2)
{
Scanner keyboard = new Scanner(System.in);
System.out.println("How many Rows would you like your matrix to have?");
Rows2 = keyboard.nextInt();
System.out.println("How many Columns would you like your matrix to have?");
Columns2 = keyboard.nextInt();
}
当RowColumns被调用Rows2被设置为Rows1且Columns2被设置为等于Columns1时，请注意您的RowColumns如何进行操作＃39;实际上影响Rows1和Columns1。在您的代码中，您通过将RowColumns的参数命名为与传递给它的变量相同来混淆自己，这意味着虽然看起来它们是相同的，但实际上它们完全不同。
对此的一个解决方案是，如果您不需要其他地方，只需取消RowColumns方法：
int Rows=0;
int Columns=0;
int [][] MatrixOne;
int [][] MatrixTwo;
do{
System.out.print("Please choose an operation: Addition(1) or Subtract(2)");
operation = keyboard.nextInt();
Scanner keyboard = new Scanner(System.in);
System.out.println("How many Rows would you like your matrix to have?");
Rows = keyboard.nextInt();
System.out.println("How many Columns would you like your matrix to have?");
Columns = keyboard.nextInt();
这可以完成同样的事情，但这次你将使用你想要的Rows和Columns变量。
如果要将用户输入保持为自己的方法，最直接的解决方案是创建两个单独的方法，一个用于获取行，另一个用于获取列，然后让这些方法返回由用户。像这样：
int Rows=0;
int Columns=0;
int [][] MatrixOne;
int [][] MatrixTwo;
do{
System.out.print("Please choose an operation: Addition(1) or Subtract(2)");
operation = keyboard.nextInt();
Rows = getRows();
Columns = getColumns();
这两种方法看起来像这样：
public static int getRows()
{
Scanner keyboard = new Scanner(System.in);
System.out.println("How many Rows would you like your matrix to have?");
return keyboard.nextInt();
}
public static int getColumns()
{
Scanner keyboard = new Scanner(System.in);
System.out.println("How many Columns would you like your matrix to have?");
return keyboard.nextInt();
}
有很多方法可以解决这个问题，我只给出了两个最直接的方法。希望这足以回答你的问题！