Java.io.Writer class in Java

Last Updated : 12 Sep, 2023

This abstract class for writing to character streams. The only methods that a subclass must implement are write(char[], int, int), flush(), and close(). Most subclasses, however, will override some of the methods defined here in order to provide higher efficiency, additional functionality, or both.
Constructor

protected Writer() : Creates a new character-stream writer whose critical sections will synchronize on the writer itself.
protected Writer(Object lock) : Creates a new character-stream writer whose critical sections will synchronize on the given object.

Methods:

Writer append(char c) : Appends the specified character to this writer.An invocation of this method of the form out.append(c) behaves in exactly the same way as the invocation
out.write(c)
```
Syntax :public Writer append(char c)
              throws IOException
Parameters:
c - The 16-bit character to append
Returns:
This writer
Throws:
IOException
```
Writer append(CharSequence csq) : Appends the specified character sequence to this writer.An invocation of this method of the form out.append(csq) behaves in exactly the same way as the invocation
out.write(csq.toString())
Depending on the specification of toString for the character sequence csq, the entire sequence may not be appended. For instance, invoking the toString method of a character buffer will return a subsequence whose content depends upon the buffer’s position and limit.
```
Syntax :public Writer append(CharSequence csq)
              throws IOException
Parameters:
csq - The character sequence to append. If csq is null, 
then the four characters "null" are appended to this writer.
Returns:
This writer
Throws:
IOException
```

Writer append(CharSequence csq, int start, int end) : Appends a subsequence of the specified character sequence to this writer.Appends a subsequence of the specified character sequence to this writer

Syntax :public Writer append(CharSequence csq,
            int start,
            int end)
              throws IOException
Parameters:
csq - The character sequence from which a subsequence will be appended. 
If csq is null, then characters will be appended as 
if csq contained the four characters "null".
start - The index of the first character in the subsequence
end - The index of the character following the last character in the subsequence
Returns:
This writer
Throws:
IndexOutOfBoundsException
IOException

abstract void close() : Closes the stream, flushing it first. Once the stream has been closed, further write() or flush() invocations will cause an IOException to be thrown. Closing a previously closed stream has no effect.
```
Syntax :public abstract void close()
                    throws IOException
Throws:
IOException 
```
abstract void flush() : Flushes the stream.If the stream has saved any characters from the various write() methods in a buffer, write them immediately to their intended destination. Then, if that destination is another character or byte stream, flush it. Thus one flush() invocation will flush all the buffers in a chain of Writers and OutputStreams.
```
Syntax :public abstract void flush()
                    throws IOException
Throws:
IOException
```

void write(char[] cbuf) : Writes an array of characters.

Syntax :public void write(char[] cbuf)
           throws IOException
Parameters:
cbuf - Array of characters to be written
Throws:
IOException - If an I/O error occurs

abstract void write(char[] cbuf, int off, int len) : Writes a portion of an array of characters.

Syntax :public abstract void write(char[] cbuf,
         int off,
         int len)
                    throws IOException
Parameters:
cbuf - Array of characters
off - Offset from which to start writing characters
len - Number of characters to write
Throws:
IOException

void write(int c) : Writes a single character.The character to be written is contained in the 16 low-order bits of the given integer value; the 16 high-order bits are ignored.
Subclasses that intend to support efficient single-character output should override this method.
```
Syntax :public void write(int c)
           throws IOException
Parameters:
c - int specifying a character to be written
Throws:
IOException
```

void write(String str) : Writes a string.

Syntax :public void write(String str)
           throws IOException
Parameters:
str - String to be written
Throws:
IOException

void write(String str, int off, int len) : Writes a portion of a string.

Syntax :public void write(String str,
         int off,
         int len)
           throws IOException
Parameters:
str - A String
off - Offset from which to start writing characters
len - Number of characters to write
Throws:
IndexOutOfBoundsException

Program :

//Java program demonstrating Writer methods 
  
import java.io.IOException; 
import java.io.PrintWriter; 
import java.io.Writer; 
class WriterDemo 
{ 
    public static void main(String[] args) throws IOException 
    { 
        Writer wr=new PrintWriter(System.out); 
        char c[] = {'B','C','D','E','F'}; 
        CharSequence cs = "JKL"; 
        String str = "GHI"; 
  
        //illustrating write(int c) 
        wr.write(65); 
          
        //flushing the stream 
        wr.flush(); 
          
        //illustrating write(char[] c,int off,int len) 
        wr.write(c); 
        wr.flush(); 
          
        //illustrating write(String str,int off,int len) 
        wr.write(str); 
        wr.flush(); 
          
        //illustrating append(Charsequence cs,int start,int end) 
        wr.append(cs); 
        wr.flush(); 
          
        //illustrating append(int ch) 
        wr.append('M'); 
        wr.flush(); 
  
        //closing the stream 
        wr.close(); 
    } 
} 