java - 为什么输入与 "-1"进行比较？

Question

当我检查示例代码时，我正在刷新 I/O 知识，我看到了一些让我困惑的东西:

public class CopyBytes {
public static void main(String[] args) throws IOException {

    FileInputStream in = null;
    FileOutputStream out = null;

    try {
        in = new FileInputStream("xanadu.txt");
        out = new FileOutputStream("outagain.txt");
        int c;

        while ((c = in.read()) != -1) {
            out.write(c);
        }

如何将 int 值 (c) 分配给输入流 (in.read()) 中的一个字节数据？为什么 while 循环要等待它不等于 -1？

Answer 1

当到达输入末尾时，此 (c = in.read()) 将返回 -1，因此 while 循环将停止。

阅读这篇精彩文章answer .

来自 Oracle 文档:

public abstract int read() throws IOException Reads the next byte of data from the input stream. The value byte is returned as an int in the range 0 to 255. If no byte is available because the end of the stream has been reached, the value -1 is returned. This method blocks until input data is available, the end of the stream is detected, or an exception is thrown. A subclass must provide an implementation of this method.

Returns: the next byte of data, or -1 if the end of the stream is reached. Throws: IOException - if an I/O error occurs.