InputStreamReader 源码分析
InputStreamReader在字节流和字符流之间架起了桥梁。能够读取字节数组并使用指定的字符集解码成字符流。每次调用InputStreamReader的read方法会从底层字节流读取一个或多个字节。为了确保有效的转换，可能会从底层流中读取更多的字节。
为了提高性能，可以考虑结合BufferedReader使用：
BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
public class InputStreamReader extends Reader { // 流解码类，所有的调用都是交给它完成。private final StreamDecoder sd;// 使用默认的字符集名来创建实例public InputStreamReader(InputStream in) {super(in);try {sd = StreamDecoder.forInputStreamReader(in, this, (String)null); // ## check lock object} catch (UnsupportedEncodingException e) {// The default encoding should always be availablethrow new Error(e);}} // 根据指定的字符集名来创建实例public InputStreamReader(InputStream in, String charsetName)throws UnsupportedEncodingException{super(in);if (charsetName == null)throw new NullPointerException("charsetName");sd = StreamDecoder.forInputStreamReader(in, this, charsetName);}// 根据指定的字符集来创建实例public InputStreamReader(InputStream in, Charset cs) {super(in);if (cs == null)throw new NullPointerException("charset");sd = StreamDecoder.forInputStreamReader(in, this, cs);}// 根据指定的字符集解码器来创建实例public InputStreamReader(InputStream in, CharsetDecoder dec) {super(in);if (dec == null)throw new NullPointerException("charset decoder");sd = StreamDecoder.forInputStreamReader(in, this, dec);}// 获取该流使用的字符编码名public String getEncoding() {return sd.getEncoding();}// 读取一个字符public int read() throws IOException {return sd.read();}// 读取一串字符到字符数组中public int read(char cbuf[], int offset, int length) throws IOException {return sd.read(cbuf, offset, length);}// 查看流是否准备好用于读取。public boolean ready() throws IOException {return sd.ready();}// 关闭Readerpublic void close() throws IOException {sd.close();}}
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