如何從txt更改多行

Question

我有一個帶有字母的文本文件，我想讓它們變成小寫字母。它的代碼，但它變成只

BufferedReader in = new BufferedReader(new FileReader("C:\Users\xxx\Desktop\j.txt")); 

     String line; 
     while((line = in.readLine()) != null) 
     { 
      blig=line.toUpperCase(); 
      }  

    try (BufferedWriter writer = new BufferedWriter(new FileWriter("C:\Users\xxx\Desktop\j.txt"))) { 
     writer.write(blig); 
    } 

Answer 1

您將在整個文件遍歷只是儲存的最後一行的最後一行。爲了讓所有的線，你需要存儲所有你正在閱讀的線條，將它們轉換爲大寫，然後將它們寫回文件：

List<String> upper = new ArrayList<>(); 
try(BufferedReader in = new BufferedReader(new FileReader("C:\Users\xxx\Desktop\j.txt"))) 
{ 
    String line; 
    while((line = in.readLine()) != null) 
    { 
     // upper.add(line.toUpperCase()); // if you need upper case 
     upper.add(line.toLowerCase()); // if you need lower case 
    }  
} 

try(BufferedWriter writer = new BufferedWriter(new FileWriter("C:\Users\xxx\Desktop\j.txt"))) 
{ 
    for(String str : upper) 
    { 
     writer.write(str); 
     writer.newLine(); // remove if not needed. 
    } 
} 

Answer 2

因爲你，而你只寫最後一行不連接所有的結果。通過

blig += line.toUpperCase() + "\\n"; 

Answer 3

BufferedReader in = new BufferedReader(new FileReader("C:\Users\xxx\Desktop\j.txt")); 
BufferedWriter writer = new BufferedWriter(new FileWriter("C:\Users\xxx\Desktop\lowerJ.txt")); 

String line; 
while((line = in.readLine()) != null) { 
    writer.write(line.toLowerCase()); 
}  

Answer 4

如果你想降低字符的大小寫 更換while語句，那麼爲什麼使用UPER？

blig=line.toUpperCase();

它被前人的精力bling的= line.toLowerCase（）;