4、实例演示：
与下面的BufferedReader结合使用实现字符类型的文件的拷贝。二：BufferedReader
1、类功能简介：
缓冲字符输入流、他的功能是为传入的底层字符输入流提供缓冲功能、他会通过底层字符输入流（in）中的字符读取到自己的buffer中（内置缓存字符数组）、然后程序调用BufferedReader的read方法将buffer中的字符读取到程序中、当buffer中的字符被读取完之后、BufferedReader会从in中读取下一个数据块到buffer中供程序读取、直到in中数据被读取完毕、这样做的好处一是提高了读取的效率、二是减少了打开存储介质的连接次数、详细的原因下面BufferedWriter有说到。其有个关键的方法fill()就是每当buffer中数据被读取完之后从in中将数据填充到buffer中、程序从内存中读取数据的速度是从磁盘中读取的十倍！这是一个很恐怖的效率的提升、同时我们也不能无禁止的指定BufferedReader的buffer大小、毕竟、一次性读取in中耗时较长、二是内存价格相对昂贵、我们能做的就是尽量在其中找到合理点。一般也不用我们费这个心、创建BufferedReader时使用buffer的默认大小就好。
2、BufferedReader API简介：
A：构造方法
BufferedReader(Reader in, int sz) 根据指定大小和底层字符输入流创建BufferedReader。br
BufferedReader(Reader in) 使用默认大小创建底层输出流的缓冲流
B：一般方法
void close() 关闭此流、释放与此流有关的所有资源
void mark(int readAheadLimit) 标记此流此时的位置
boolean markSupported() 判断此流是否支持标记
void reset() 重置in被最后一次mark的位置
boolean ready() 判断此流是否可以读取字符
int read() 读取单个字符、以整数形式返回。如果读到in的结尾则返回-1。
int read(char[] cbuf, int off, int len) 将in中len个字符读取到cbuf从下标off开始长度len中
String readLine() 读取一行
long skip(long n) 丢弃in中n个字符
3、源码分析
package com.chy.io.original.code;
import java.io.IOException;
/**
* 为底层字符输入流添加字符缓冲cb数组。提高效率
* @version 1.1, 13/11/17
* @author andyChen
*/
public class BufferedReader extends Reader {
private Reader in;
private char cb[];
private int nChars, nextChar;
private static final int INVALIDATED = -2;
private static final int UNMARKED = -1;
private int markedChar = UNMARKED;
private int readAheadLimit = 0; /* Valid only when markedChar > 0 */
/** If the next character is a line feed, skip it */
private boolean skipLF = false;
/** The skipLF flag when the mark was set */
private boolean markedSkipLF = false;
private static int defaultCharBufferSize = 8192;
private static int defaultExpectedLineLength = 80;
/**
* 根据指定大小和底层字符输入流创建BufferedReader。br
*/
public BufferedReader(Reader in, int sz) {
super(in);
if (sz <= 0)
throw new IllegalArgumentException("Buffer size <= 0");
this.in = in;
cb = new char[sz];
nextChar = nChars = 0;
}
/**
* 使用默认大小创建底层输出流的缓冲流
*/
public BufferedReader(Reader in) {
this(in, defaultCharBufferSize);
}
/** 检测底层字符输入流in是否关闭 */
private void ensureOpen() throws IOException {
if (in == null)
throw new IOException("Stream closed");
}
/**
* 填充cb。
*/
private void fill() throws IOException {
int dst;
if (markedChar <= UNMARKED) {
/* No mark */
dst = 0;
} else {
/* Marked */
int delta = nextChar - markedChar;
if (delta >= readAheadLimit) {
/* Gone past read-ahead limit: Invalidate mark */
markedChar = INVALIDATED;
readAheadLimit = 0;
dst = 0;
} else {
if (readAheadLimit <= cb.length) {
/* Shuffle in the current buffer */
System.arraycopy(cb, markedChar, cb, 0, delta);
markedChar = 0;
dst = delta;
} else {
/* Reallocate buffer to accommodate read-ahead limit */
char ncb[] = new char[readAheadLimit];
System.arraycopy(cb, markedChar, ncb, 0, delta);
cb = ncb;
markedChar = 0;
dst = delta;
}
nextChar = nChars = delta;
}
}
int n;
do {
n = in.read(cb, dst, cb.length - dst);
} while (n == 0);
if (n > 0) {
nChars = dst + n;
nextChar = dst;
}
}
/**
* 读取单个字符、以整数形式返回。如果读到in的结尾则返回-1。
*/
public int read() throws IOException {
synchronized (lock) {
ensureOpen();
for (;;) {
if (nextChar >= nChars) {
fill();
if (nextChar >= nChars)
return -1;
}
if (skipLF) {
skipLF = false;
if (cb[nextChar] == '\n') {
nextChar++;
continue;
}
}
return cb[nextChar++];
}
}
}
/**
* 将in中len个字符读取到cbuf从下标off开始长度len中
*/
private int read1(char[] cbuf, int off, int len) throws IOException {
if (nextChar >= nChars) {
/* If the requested length is at least as large as the buffer, and
if there is no mark/reset activity, and if line feeds are not
being skipped, do not bother to copy the characters into the
local buffer. In this way buffered streams will casc