缓冲阅读器和扫描仪

我想知道这是怎么回事。它给了我一个构造函数错误（java.io.InputSream）

BufferedReader br = new BufferedReader(System.in);
String filename = br.readLine();

BufferedReader 是装饰另一个阅读器的装饰器。 InputStream 不是读取器。您首先需要一个InputStreamReader。

BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

为了回应您的评论，这里是 readline 的 javadoc：

readLine

public String readLine()
                throws IOException

    Read a line of text. A line is considered to be terminated by any one of a line feed ('\n'), a carriage return ('\r'), or a carriage return followed immediately by a linefeed.

    Returns:
        A String containing the contents of the line, not including any line-termination characters, or null if the end of the stream has been reached 
    Throws:
        IOException - If an I/O error occurs

为了正确处理这个问题，您需要将方法调用放在 try/catch 块中，或者声明它可以被抛出。

使用 try/catch 块的示例：

BufferedReader br = new BufferedReader (new InputStreamReader(System.in));

try{
    String filename = br.readLine();
} catch (IOException ioe) {
    System.out.println("IO error");
    System.exit(1);
} 

声明可能抛出异常的示例：

void someMethod() throws IOException {
    BufferedReader br = new BufferedReader (new InputStreamReader(System.in));
    String filename = br.readLine();
}