java - 如果文件不存在，readAllLines 会返回什么？

Question

oracle 文档说 here那Files.readAllLines(Path path, Charset cs)方法将文件中的行作为 List<String> 返回.
如果文件不存在会返回什么？还有哪个实现 List<String>它会回来吗？

Answer 1

这里是 Files#readAllLines(Path, Charset) 抛出的异常

它实际上使用了一个 try-with-ressources 来实例化一个 BufferedReader与 path作为参数。如果文件不存在，一个 IOException不是由它在构造函数中抛出。

Throws:

java.io.IOException if an I/O error occurs reading from the file or a malformed or unmappable byte sequence is read

java.lang.SecurityException In the case of the default provider, and a security manager is installed, the checkRead method is invoked to check read access to the file.

---

安ArrayList<String>用作 List<String> 的确切实现

public static List<String> readAllLines(Path path, Charset cs) throws IOException {
    try (BufferedReader reader = newBufferedReader(path, cs)) {
        List<String> result = new ArrayList<>();           <-------- HERE
        for (;;) {
             String line = reader.readLine();
             if (line == null)
                 break;
             result.add(line);
        }
        return result;
    }
}