抛出并捕获IOException

Question

   inputFileName = "2.txt";
   outputFileName = "3.txt";

   inputFile = new BufferedReader(new FileReader(inputFileName));
   outputFile = new PrintWriter(new FileWriter(outputFileName));

   String lineOfText = inputFile.readLine();

   while (lineOfText != null)
   {
       if (lineOfText.contains("x"))
       {
           lineOfText = lineOfText.replaceAll("x"+ ".*", "");
       } 
       outputFile.println(lineOfText);
       lineOfText = inputFile.readLine();
   } 

   inputFile.close();
   outputFile.close();

你好，现在我有一个输入和输出，这是否意味着我有两个try和两个catch块（连接到前一个文件并写入第二个文件可能有错误）。或者我只需要一个试块？

如果是这样，我将如何/在哪里实现try和catch块？

Answer 1

我只会通过编写一个try / catch / finally-block来使用：

try {
    inputFile = new BufferedReader(new FileReader(inputFileName));
    outputFile = new PrintWriter(new FileWriter(outputFileName));
    String lineOfText = inputFile.readLine();
    while (lineOfText != null) {
        if (lineOfText.contains("x")) {
            lineOfText = lineOfText.replaceAll("x"+ ".*", "");
        } 
        outputFile.println(lineOfText);
        lineOfText = inputFile.readLine();
    } 
} catch(IOException ioe) {
        System.err.println("Caught IOException: " + ioe.getMessage());
} finally {
    if(inputFile != null)
        inputFile.close();
    if(outputFile != null)
        outputFile.close();
}

通过使用finally块，您可以确定Reader和Writer对象肯定是关闭的。

Answer 2

我建议使用Java 7的try with resources块，如下面的例子所示，它将处理资源的closing：

public static void main(String[] args) throws Exception {
    String inputFileName = "2.txt";
    String outputFileName = "3.txt";
    try (BufferedReader inputFile = new BufferedReader(new FileReader(inputFileName));
            PrintWriter outputFile = new PrintWriter(new FileWriter(outputFileName));) {
        String lineOfText = inputFile.readLine();

        while (lineOfText != null) {
            if (lineOfText.contains("x")) {
                lineOfText = lineOfText.replaceAll("x" + ".*", "");
            }
            outputFile.println(lineOfText);
            lineOfText = inputFile.readLine();
        }
    }catch(Exception e){
        //Handle
    }
}

Here是try with resources的文档。