java - 切换问题，阵列打印

Question

- 所以在情况 2 中，我试图让用户仅输入具有特定数组位置的元素(N，Y，P，D，G)。我在 switch 中使用了 switch，但是如果他输入了错误的元素，我该如何重新循环？

-在情况 3 中，我试图打印整个 2D 数组，但原始数组填充了元素 G。

-在情况 4 中，我尝试将 map View 更改为符号。

只是发现这是一种练习，试图在某种程度上学习初学者复杂的编程，因此任何帮助都将受到赞赏，任何批评都将受到高度赞赏，因为我想拥有良好的 java 基础知识:)

import java.util.Scanner;

public class Studyone {

public static void main(String[] args) 
{
    Scanner input = new Scanner(System.in);
    int row;
    int col;
    int row1; //for case 2, so it would allow the user to input the element in the request array
    int col1;
    System.out.println("Enter the row: ");// knowing the row and the col of the 2D array to base the rest on.
    row = input.nextInt();
    System.out.println("Enter the col: ");
    col = input.nextInt();
    String sentence;
    String sentence2;
    String sentence3;
    String tempelement;
    String N;
    String Y;
    String G;
    String P;
    String D;
    int choice;
    System.out.println("The menu\n1)Enter the Elements in order\n2)Enter the the Col and row number spec.\n3)Show the Orig. map as is\n4)Show symbolic map.");
    choice = input.nextInt();
    System.out.println(choice);
    String [][] map = new String[row][col];
    switch (choice)
    {
        case 1:
            sentence3=input.nextLine();  // for some reason it auto enters the first map [0][0] as null, this line allows the user to input the map[0][0]
            map[0][0]=sentence3;
            for (int i = 0; i < map.length; i++) 
            {
                for (int j = 0;j < map[i].length; j++) 
                {
                    System.out.println("Enter the element");
                    sentence2 = input.nextLine();
                    map[i][j]=sentence2;
                }
                System.out.println(map[1][1]);
                System.out.println(choice);

            }
            break;
        case 2:
            System.out.println("Enter the row");
            row1 = input.nextInt();
            System.out.println("Enter the col");
            col1 = input.nextInt();
            System.out.println("Enter the element you want to enter");
            tempelement = input.nextLine();
            switch (tempelement)
            {
                case "Y":
                    map[row1][col1] = tempelement;
                case "N":
                    map[row1][col1] = tempelement;
                case "P":
                    map[row1][col1] = tempelement;
                case "D":
                    map[row1][col1] = tempelement;
                case "G":
                    map[row1][col1] = tempelement;
            }

            System.out.println(tempelement);  // test,does not let me enter any temp elements, lets it empty in the input without letting the use enter anything. Figure out error
            System.out.println(choice); // test, prints the right choice, Correct.
            break;
        case 3:
            for (int i=0;i > map.length;i++)
            {
                for (int j=0; j > map[i].length; j++)
                {
                    map[i][j] = N;
                    // print statment, need to find how to do.
                }
            }**strong text**
        break;
        case 4:
            // having symbols instead of the letters, N=* , P= ~ , Y=. , G= #, D=@
            //
    }
}
}

Answer 1

情况2:

我不知道为什么你要在其中使用 switch 语句来检查情况是否是 N、Y、P、D 或 G。为了检查输入是否正确，你可以使用 while 循环并中断当放置正确的输入时。

 System.out.println("Enter the row");
 row1 = input.nextInt();
 System.out.println("Enter the col");
 col1 = input.nextInt();

 while(true){
 System.out.println("Enter the element you want to enter");
 tempelement = input.nextLine();
 if(tempelement.equals("N") || tempelement.equals("Y") || tempelement.equals("P") || tempelement.equals("D") || tempelement.equals("G")){
     map[row1][col1] = tempelement;
     break;
  }
 }

情况3:

要打印二维数组，您需要一个嵌套的 for 循环。它需要 2 个 for 循环。

for(int i=0; i<map.length; i++){
    for(int j=0; j<map[i].length; j++){
          System.out.print(map[i][j]);
     }
      System.out.print("\n");  // this is for spacing after a row of element prints
 }

案例4:

这与情况 3 相同，只是在内部 for 循环内，您将有一个 if-else 语句 block 或 switch block 来打印符号而不是映射。例如，

...
    for(int j=0; j<map[i].length; j++){
       switch(map[i][j]){
              case "N": System.out.print("Symbol"); break;
              case "P": ... code
             ... code
        }
    }