Java Java.io.FilterReader用法及代码示例

用于读取过滤字符流的抽象类。抽象类FilterReader本身提供了将所有请求传递到所包含流的默认方法。 FilterReader 的子类应该重写其中一些方法，并且还可以提供其他方法和字段。
构造函数：

• protected FilterReader(读入)：创建一个新的过滤阅读器。

方法：

• 无效close()：关闭流并释放与其关联的所有系统资源。关闭流后，进一步的 read()、ready()、mark()、reset() 或 skip() 调用将引发 IOException。关闭之前关闭的流没有任何效果。

  Syntax :public void close()
             throws IOException
  Throws:
  IOException

• 无效标记(int readAheadLimit)：标记流中的当前位置。

  Syntax :public void mark(int readAheadLimit)
            throws IOException
  参数：
  readAheadLimit - Limit on the number of characters that may be read 
  while still preserving the mark. After reading this many characters,
   attempting to reset the stream may fail.
  Throws:
  IOException

• 布尔值markSupported()：告知此流是否支持mark()操作。

  Syntax :public boolean markSupported()
  返回：
  true if and only if this stream supports the mark operation.

• int read()：读取单个字符。

  Syntax :public int read()
           throws IOException
  Returns:
  The character read, as an integer in the range 0 to 65535 (0x00-0xffff), 
  or -1 if the end of the stream has been reached
  Throws:
  IOException

• int 读取(char[] cbuf，int 关闭，int len)：将字符读入数组的一部分。

  Syntax :public int read(char[] cbuf,
         int off,
         int len)
           throws IOException
  参数：
  cbuf - Destination buffer
  off - Offset at which to start storing characters
  len - Maximum number of characters to read
  返回：
  The number of characters read, or -1 if the end of the stream has been reached
  Throws:
  IOException

• 布尔值ready()：告知该流是否已准备好读取。

  Syntax :public boolean ready()
                throws IOException
  返回：
  True if the next read() is guaranteed not to block for input, 
  false otherwise. Note that returning false does not guarantee
  that the next read will block.
  Throws:
  IOException

• 无效reset()：重置流。

  Syntax :public void reset()
             throws IOException
  Throws:
  IOException

• 长跳过(长n)：跳过字符。

  Syntax :public long skip(long n)
            throws IOException
  参数：
  n - The number of characters to skip
  返回：
  The number of characters actually skipped
  Throws:
  IOException

程序：

//Java program illustrating FilterReader class methods 
  
import java.io.*; 
class FilterReaderdemo 
{ 
    public static void main(String[] args) throws IOException 
    { 
        Reader r = new StringReader("GeeksforGeeks"); 
        FilterReader fr = new FilterReader(r)  
        { 
        }; 
        char ch[] = new char[8]; 
          
        //illustrating markSupported() 
        if(fr.markSupported()) 
        { 
            //illustrating mark() method 
            System.out.println("mark method is supported"); 
            fr.mark(100); 
        } 
          
        //illustrating skip() method 
        fr.skip(5); 
          
        //illustrating ready() 
        if(fr.ready()) 
        { 
            //illustrating read(char[] cbuff,int off,int len) 
            fr.read(ch); 
            for (int i = 0; i < 8; i++)  
            { 
                System.out.print(ch[i]); 
            } 
              
            //illustrating reset() 
            fr.reset(); 
            for (int i = 0; i <5 ; i++) 
            { 
                //illustrating read() 
                System.out.print((char)fr.read()); 
            } 
        } 
          
        //closing the stream 
        fr.close(); 
    } 
} 

输出：

mark method is supported
forGeeksGeeks