Java IO 操作流之回退流-输入流的增强版

2015-07-11 10:21:42 暂无评论奇妙冰淇淋随笔杂文 1,093

回退流失输入流的一种，具体用法如下：

public class PushbackInputStream extends FilterInputStream；// 字节输入回退流；
public PushbackInputStream(InputStream in,
                           int size)
    Creates a PushbackInputStream with a pushback buffer of the specified size, and saves its argument, the input stream in, for later use. Initially, there is no pushed-back byte (the field pushBack is initialized to -1).
public PushbackInputStream(InputStream in)；// 可以接收所有字节输入流
    Creates a PushbackInputStream and saves its argument, the input stream in, for later use. Initially, there is no pushed-back byte (the field pushBack is initialized to -1).
public int read()
         throws IOException
    Reads the next byte of data from this input stream. The value byte is returned as an int in the range 0 to 255.
public void unread(int b)
            throws IOException；// 回退一字节的数据，
    Pushes back a byte by copying it to the front of the pushback buffer. After this method returns, the next byte to be read will have the value (byte)b.
public void unread(byte[] b, int off,int len) throws IOException ;
public void close()
           throws IOException;
2. public class PushbackReader extends FilterReader;// 字符输入回退流，对所有字符输入流的增强！
A character-stream reader that allows characters to be pushed back into the stream.
———回退内存输入流的实例：
package com.mldn;
import java.io.InputStream;
import java.io.ByteArrayInputStream;
import java.io.PushbackInputStream;
import java.io.IOException;
public class PushbackDemo
{
        public static void main(String[] args) throws IOException
        {
                byte[] bytes = null;        // 声明字节内存
                bytes = new String(“Hello, World!”).getBytes();        // 实例化内存数组
                InputStream input = null;// 声明字节输入流
                PushbackInputStream pis = null;        // 声明字节输入回退流
                input = new ByteArrayInputStream(bytes);        // 实例化内存输入流
                pis = new PushbackInputStream(input);                // 实例化字节输入回退流
                int temp = 0;
                StringBuffer pushback = new StringBuffer();
                StringBuffer str = new StringBuffer();
                while ((temp = pis.read()) != -1)
                {
                        if (temp == ‘,’)        // 若读的是’,’,回退到输入流缓冲区
                        {
                                pis.unread(temp);// 回退一个字节
                                pushback.append((char)pis.read());         // 将回退的字节读出到匿名变量
                        }
                        else
                        {
                                str.append((char)temp);
                        }
                }
                System.out.println(“回退数据：'” + pushback.toString() + “‘! ” + pushback.length() + “次!”);
                System.out.println(“读取的内容为：”);
                System.out.println(str);
        }
}
/*
administrator@xu-desktop:~$ java com.mldn.PushbackDemo
回退数据：’,’! 1次!
读取的内容为：
Hello World!
*/