java为什么输入与“1”相比？

Question

当我浏览示例代码时，我正在刷新自己的I/O，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）分配给来自输入流（in.read（））的数据字节？while循环为什么要等待它不等于-1呢

Answer 1

从FileInputStream.read()的文档中：

public int read() throws IOException

因此read（）返回整数，而不是字节，因此可以将其分配给int变量。 请注意，整数可以隐式转换为整数，而不会丢失。也可以从文档中看到：

Returns: the next byte of data, or -1 if the end of the file is reached.

针对-1的循环检查确定是否已到达文件结尾，如果已到达，则停止循环

Answer 2

当到达输入端时，这个(c = in.read())将返回-1，因此while循环将停止

读这篇很棒的answer

从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.