Java.io.StringReader class in Java

StringReader class in Java is a character stream class whose source is a string. It inherits Reader Class. Closing the StringReader is not necessary, it is because system resources like network sockets and files are not used. Let us check more points about StringReader Class in Java.

Declare StringReader Class in Java

public class StringReader extends Reader  

Constructor in Java StringReader Class

The constructor used with StringReader Class in Java is mentioned below:

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

Methods in Java StringReader Class

Methods in StringReader Class in Java are mentioned below:

Method	Description
int read()	Reads a single character
int read(char[] cbuf, int off, int len)	Reads characters into a portion of an array
boolean ready()	Tells whether this stream is ready to be read
boolean markSupported()	Tells whether stream support mark
void mark(int readAheadLimit)	Marks the mark present in the position present in the stream
void reset()	Resets the stream to the most recent mark, or to the beginning of the string if it has never been marked.
long skip(long ns)	Resets specified number of characters in a stream
void close()	Closes the stream

1. 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

2. 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

3. 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

4. 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.

5. 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

6. 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 

7. long skip(long ns)

It 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

8. 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()

Example

Java

// Java program demonstrating StringReader methods
import java.io.IOException;
import java.io.StringReader;

// Driver class
class StringReaderDemo {
    // main function
    public static void main(String[] args)
        throws IOException
    {
        StringReader str = new StringReader(
            " GeeksforGeeks & quot;);
        char c[] = new char[7];

        // illustrating markSupported()
        if (str.markSupported()) {
            System.out.println(
                " Mark method is supported & quot;);
            // 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 & lt; 7; i++) {
                System.out.print(c[i]);
            }
        }

        // illustrating reset() method
        str.reset();

        for (int i = 0; i & lt; 5; i++) {
            System.out.print((char)str.read());
        }

        // illustrating close()
        str.close();
    }
}

Output

Mark method is supported
forGeeksGeeks