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Java 在没有语法错误的情况下正确调用此方法时，为什么要跳过此方法？

java methods matrix

Java 在没有语法错误的情况下正确调用此方法时，为什么要跳过此方法？,java,methods,matrix,Java,Methods,Matrix,下面是正在发生的事情的基本代码。我已经提示输入行数和列数，这很有效。问题是，一旦程序到达“输入数据…”，它就会打印数据，但会完全忽略对矩阵的调用。在矩阵的内部我也会提示使用scanner类输入矩阵。而且，我意识到这一点目前还没有结束。请帮忙 case 1: System.out.println("Enter the data for the first matrix."); //input needed MatrixOne

下面是正在发生的事情的基本代码。我已经提示输入行数和列数，这很有效。问题是，一旦程序到达
“输入数据…”
，它就会打印数据，但会完全忽略对
矩阵的调用。在
矩阵的内部
我也会提示使用scanner类输入矩阵。而且，我意识到这一点目前还没有结束。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;


方法如下：


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;
}



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();
}


这是最重要的：


  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);


这就是方法：


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;
}



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();
}


和
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



在矩阵方法中，如果行或列为零，则不会进入循环；因此，它们的值可能为零。
Java是

在
RowColumns
函数中，您将
通过值传递两个整数
，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，在调用
RowColumns（Rows，Columns）
之后，
Rows
和
Columns
变量将与其初始值（0，0）保持相同

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一个容器：


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;
}



您的代码实际上调用的是
矩阵
方法，问题在于
行列
方法。您的
RowColumns
方法实际上并没有设置您认为是的变量，因此当调用
Matrix
方法时，传递给它的行和列变量为零

让我详细说明到底发生了什么。在java中，整数是通过值传递的，而不是通过引用传递的。这意味着当您调用
RowColumns（行，列）时真正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，但它们不是相同的变量。下面是查看代码的另一种方法


int Rows1=0;
int Columns1=0;
RowColumns(Rows1, Columns1);


以及您的
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();
}


当调用
RowColumns
时，将
Rows2
设置为等于
Rows1
，
Columns2
设置为等于
Columns1
，请注意
RowColumns
实际上不会影响
Rows1
和
Columns1
。在您的代码中，您将
RowColumns
的参数命名为与传递给它的变量相同，这意味着虽然它们看起来相同，但实际上完全不同

解决此问题的一个方法是，如果您不需要
RowColumns
方法，只需在其他类似的地方取消该方法：


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();



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();



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();
}


这将完成同样的事情，但这次您将使用希望使用的
行
和
列
变量

如果希望将用户输入保留到自己的方法中，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用户给定的值。大概是这样的：


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();



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();



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();
}


这两种方法看起来是这样的：


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();



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();



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();
}



解决这个问题的方法有很多种，我只给出了两种最直接的方法。希望这足以回答你的问题
 在
扫描仪的缓冲区中似乎仍有回车符/换行符。在Java中，尝试在每个
keyboard.nextLine
之后添加
keyboard.nextLine
，请对方法使用camalCase，对类使用PascalCase。您在哪里读取行和列的值？我不确定MadProgrammerRows和columns在一个单独的方法中，并在cases上面调用，这是什么意思，但输入2后，它们的值为2。对吗？试着在循环中打印i和j，因为我将初始化的行和列更改为2，它就运行了。我还是不明白为什么。你能解释一下吗？向我们展示整个main方法。行和列变量是全局变量吗？如果没有，它们将只在方法内部受到影响。将变量更改为CAMELCASE，这就是为什么查看所有代码非常重要的原因。