Java 永远不会在相应的 try 语句体中抛出异常 IOException？

Question

通常这是一个简单的问题，我可以在 StackExchange 上搜索，但我发现的其他问题似乎与我现在所处的情况不同。

filename = stdin.readLine().trim();
FileWriter fw2 = new FileWriter (filename);
BufferedWriter bw2 = new BufferedWriter (fw2);
PrintWriter outFile2 = new PrintWriter (bw2);
try {
    outFile2.print(office1);
    System.out.print(filename+" was written\n");
}
catch (IOException e) {
    System.out.print(filename+" was not found\n");
}
finally {
    outFile2.close();
}

显然，编译器声称由于某种原因此 try 块未抛出 IOException。此外，另一个需要注意的细节是 office1 是一个初始化和实例化的对象。现在这就是棘手的地方。编译器（在我写这段代码之前）声称下一段代码完全没问题：

filename = stdin.readLine().trim();
FileWriter fw = new FileWriter (filename);
BufferedWriter bw = new BufferedWriter (fw);
PrintWriter outFile = new PrintWriter (bw);
try {
    String input = stdin.readLine().trim();
    System.out.print("Please enter a string to write in the file:\n");
    outFile.print (input+"\n");
    System.out.print(filename+" was written\n");
}
catch (IOException exception) {
    System.out.println (filename+ " was not found");
}
finally {
    outFile.close();
}

编译器一直抱怨上面的代码没有抛出 IOException 而下面的代码却抛出 IOException 有什么原因吗？

Answer 1

您的 outfile2 是 PrintWriter。有点意外，PrintWriter methods don't throw exceptions.

Methods in this class never throw I/O exceptions, although some of its constructors may. The client may inquire as to whether any errors have occurred by invoking checkError().

这就解释了为什么您的第一个代码没有抛出 IOException。

在您的第二个代码中，您添加了对 readLine() 的调用，可能来自 BufferedReader，它会抛出 IOException.

Java 永远不会在相应的 try 语句体中抛出异常 IOException？

Java exception IOException is never thrown in body of corresponding try statement?

java

error-handling

compiler-errors

ioexception