Класс Java.io.StringReader в Java

Опубликовано: 15 Февраля, 2022

Это класс символьного потока, источником которого является строка.
Конструктор:

StringReader(String s) : Creates a new string reader.

Methods :

void close() : Closes the stream and releases any system resources associated with it.Once the stream has been closed, further read(), ready(), mark(), or reset() invocations will throw an IOException. Closing a previously closed stream has no effect.
```
Syntax :public void close()
```

void mark(int readAheadLimit) : Marks the present position in the stream. Subsequent calls to reset() will reposition the stream to this point.

Syntax :public void mark(int readAheadLimit)
          throws IOException
Parameters:
readAheadLimit - Limit on the number of characters that may 
be read while still preserving the mark. Because the stream"s input 
comes from a string, there is no actual limit, so this argument 
must not be negative, but is otherwise ignored.
Throws:
IllegalArgumentException
IOException

boolean markSupported() : Tells whether this stream supports the mark() operation, which it does.

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

int read() : Reads a single character.

Syntax :public int read()
         throws IOException
Returns:
The character read, or -1 if the end of the stream has been reached
Throws:
IOException

int read(char[] cbuf, int off, int len) : Reads characters into a portion of an array.

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

boolean ready() : Tells whether this stream is ready to be read.

Syntax :public boolean ready()
              throws IOException
Returns:
True if the next read() is guaranteed not to block for input
Throws:
IOException

void reset() : Resets the stream to the most recent mark, or to the beginning of the string if it has never been marked.
```
Syntax :public void reset()
           throws IOException
Throws:
IOException 
```
long skip(long ns) : Skips the specified number of characters in the stream.. Returns the number of characters that were skipped.
The ns parameter may be negative, even though the skip method of the Reader superclass throws an exception in this case. Negative values of ns cause the stream to skip backwards. Negative return values indicate a skip backwards. It is not possible to skip backwards past the beginning of the string.
If the entire string has been read or skipped, then this method has no effect and always returns 0.
```
Syntax :public long skip(long ns)
          throws IOException
Parameters:
ns - The number of characters to skip
Returns:
The number of characters actually skipped
Throws:
IOException
```

Program :

//Java program demonstrating StringReader methods
import java.io.IOException;
import java.io.StringReader;
class StringReaderDemo
{
    public static void main(String[] args) throws IOException
    {
        StringReader str = new StringReader("GeeksforGeeks");
        char c[]=new char[7];
  
        //illustrating markSupported()
        if(str.markSupported())
        {
            System.out.println("Mark method is supported");
            // illustrating mark()
            str.mark(100);
        }
          
        //illustrating skip() method
        str.skip(5);
          
        //whether this stream is ready to be read.
        if(str.ready())
        {
            //illustrating read() method
            System.out.print((char)str.read());
              
            //illustrating read(char cff[],int off,int len)
            str.read(c);
            for (int i = 0; i <7 ; i++) 
            {
                System.out.print(c[i]);
            }
        }
          
        //illustrating reset() method
        str.reset();
          
        for (int i = 0; i < 5; i++) 
        {
            System.out.print((char)str.read());
        }
          
        //illustrating close()
        str.close();
    }
}

Output :

Mark method is supported
forGeeksGeeks

This article is contributed by Nishant Sharma. If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

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Класс Java.io.StringReader в Java

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