如何在文件数组中打印

Soo, I have to insert list of arrays into a specific text document. The array list is inset by user at case 1 and it works well. When I try call case 4 without any data, the file is created and also it's empty. When I do this with an array list I get the Error message from catch. How can I fix it?Soo, I have to insert list of arrays into a spe