Java IO体系之Reader

介绍

Abstract class for reading character streams. The only methods that a subclass must implement are read(char[], int, int) and close(). Most subclasses, however, will override some of the methods defined here in order to provide higher efficiency, additional functionality, or both. 字符输入流 程序 <<<----（输入）---- 文件

IO体系图

源码分析

继承关系

public abstract class Reader implements Readable, Closeable {

成员变量

/** * The object used to synchronize operations on this stream. */ protected Object lock; /** Maximum skip-buffer size */ private static final int maxSkipBufferSize = 8192; /** Skip buffer, null until allocated */ private char skipBuffer[] = null;

构造函数

/** * Creates a new character-stream reader whose critical sections will * synchronize on the reader itself. */ protected Reader() { this.lock = this; } /** * Creates a new character-stream reader whose critical sections will * synchronize on the given object. * @param lock The Object to synchronize on. */ protected Reader(Object lock) { if (lock == null) { throw new NullPointerException(); } this.lock = lock; }

成员方法

/** * Attempts to read characters into the specified character buffer. */ public int read(java.nio.CharBuffer target) throws IOException { int len = target.remaining(); char[] cbuf = new char[len]; int n = read(cbuf, 0, len); if (n > 0) target.put(cbuf, 0, n); return n; } /** * Reads a single character. */ public int read() throws IOException { char cb[] = new char[1]; if (read(cb, 0, 1) == -1) return -1; else return cb[0]; } /** * Reads characters into an array. */ public int read(char cbuf[]) throws IOException { return read(cbuf, 0, cbuf.length); } /** * Reads characters into a portion of an array. */ abstract public int read(char cbuf[], int off, int len) throws IOException; public long skip(long n) throws IOException { if (n < 0L) throw new IllegalArgumentException("skip value is negative"); int nn = (int) Math.min(n, maxSkipBufferSize); synchronized (lock) { if ((skipBuffer == null) || (skipBuffer.length < nn)) skipBuffer = new char[nn]; long r = n; while (r > 0) { int nc = read(skipBuffer, 0, (int)Math.min(r, nn)); if (nc == -1) break; r -= nc; } return n - r; } } /** * Tells whether this stream is ready to be read. */ public boolean ready() throws IOException { return false; } /** * Tells whether this stream supports the mark() operation. */ public boolean markSupported() { return false; } /** * Marks the present position in the stream. */ public void mark(int readAheadLimit) throws IOException { throw new IOException("mark() not supported"); } /** * Resets the stream. */ public void reset() throws IOException { throw new IOException("reset() not supported"); } /** * Closes the stream and releases any system resources associated with * it. */ abstract public void close() throws IOException;