Java 如何使用2d数组加密和解密字符串？

实际上，我使用2d数组对普通字符串进行了加密和解密

下面是我的加密代码：

import java.util.Scanner;

public class Secret {

    public static void  main(String[] args) {
        Scanner x = new Scanner(System.in);
        
        System.out.println("Enter a sentence that need to be encrypt : ");
        String y = x.nextLine();
    
        int len = y.length();
        
        System.out.println("The length of the sentences is : " + len);
        
        System.out.print("Enter number of column : " );
        int arr = x.nextInt();  
        
        char [] [] z = new char [6] [arr];
        
        // fill the character into array //
        int pos = 0;
        for (int i = 0; i<z.length; i++) {
            for (int j = 0; j<z[i].length; j++) {
                z[i][j] = y.charAt(pos);
                pos++;
        
                    }
            }
             // output the encrypted text by reading the array downward, column by
column.//
              for (int j = 0; j<z[arr].length; j++) {
                    System.out.print(z[0][j] + "" + z[1][j] + "" + z[2][j] + "" + z[3][j] + "" + z[4][j] 
            + "" + z[5][j]);}   
            }
    }

输出：

HloWrdel ol. 

Hello World.

但是我想要的输出是这样的

HloWrdel*ol…

，这意味着空间被

“*”

替换，如果有额外的空数组，则打印

“

”

现在，我的数组大小取决于字符串长度，所以当我输入arr=3（6x3=18）时，它会显示如下错误

Enter a sentence that need to be encrypt : 
Hello World.
The length of the sentences is : 12
Enter number of column : 3
Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: 12
    at java.base/java.lang.StringLatin1.charAt(StringLatin1.java:48)
    at java.base/java.lang.String.charAt(String.java:711)
    at Secret.main(Secret.java:33)

因此，我的问题是如何得到这样的理想输出

HloWrdel*ol…

？空间变为

“*”

，输入数组大小没有限制。当我输入大于字符串长度的数组大小（列）时，字符串的字符将自动填充数组，多余的空数组将打印

“

”

对于解密代码：

    import java.util.Scanner;
    public class Secret1 {
    
        public static void main(String[] args) {
        
        Scanner x = new Scanner(System.in);
        
        System.out.println("Enter the sentences that need to decrypt : ");
        String str = x.nextLine();
        
        int len = str.length();
        
        System.out.println("The number of length is " + len);
        
        System.out.println("Enter the number of rows : " );
        int arr = x.nextInt();
        
        char [][] z = new char [arr][6];
        
        // fill character into array //
        int pos = 0;
        for(int i = 0; i<z.length; i++) {
            for(int j = 0; j<z[i].length; j++) {
                z[i][j] = str.charAt(pos);
                pos++ ;
        }
        
        }
        
        //output the decrypted text by reading the array from left to right, row by
row.//
        for (int i = 0; i<z.length; i++) {
            System.out.print(z[i][0]);
        }
        
        for (int i = 0; i<z.length; i++) {
            System.out.print(z[i][1]);
        }
        
        for (int i = 0; i<z.length; i++) {
            System.out.print(z[i][2]);
        }
        
        for (int i = 0; i<z.length; i++) {
            System.out.print(z[i][3]);
        }
        
        for (int i = 0; i<z.length; i++) {
            System.out.print(z[i][4]);
        }
        
        for (int i = 0; i<z.length; i++) {
            System.out.print(z[i][5]);
        }
            }
            
            }
    

输出：

HloWrdel ol. 

Hello World.

但是我想要的输出是从加密文本

HloWrdel*ol…

到纯文本

Hello World.

。我如何获得这样的输出

此外，解密代码还取决于字符串长度，因此当我输入大于字符串长度的数组大小时，它显示如下：

Enter the sentences that need to decrypt : 
HloWrdel ol.
The number of length is 12
Enter the number of rows : 
3
Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: 12
    at java.base/java.lang.StringLatin1.charAt(StringLatin1.java:48)
    at java.base/java.lang.String.charAt(String.java:711)
    at Secret1.main(Secret1.java:147)

---

我输入的数组大小是否可能不限于字符串长度，而是在填充到数组中后不为额外的空数组打印任何内容？

在最里面的循环中（对于（int j=0；j=len）的

，如果是，请跳过尝试读取2D元素并用“.”填充

if (pos>=len)
{
    z[i][j]='.';
    continue;
}

//your normal code

然后在填充元素后，检查是否刚刚填充了空间

if (z[i][j]==' ')
    z[i][j]='*';