Clase Java.io.StringWriter en Java

La clase java.io.StringWriter crea una string a partir de los caracteres del flujo de String Buffer. Los métodos de la clase StringWriter también se pueden llamar después de cerrar el flujo, ya que esto no generará una excepción de E/S. 

Declaración :  

public class StringWriter
  extends Writer

Constructores :  

• StringWriter() : crea un nuevo StringWriter utilizando el tamaño inicial o predeterminado de String Buffer
• StringWriter (tamaño int): crea un nuevo StringWriter usando el tamaño mencionado de String Buffer

Métodos:  

• write(int char) : java.io.StringWriter.write(int char) escribe un solo carácter en el String Buffer. 
  Sintaxis: 

public void write(int char)
Parameters : 
char : int value of the character to be written.
Return  :
void

• write(String str) : java.io.StringWriter.write(String str) escribe una string en el búfer de strings. 
  Sintaxis: 

public void write(String str)
Parameters : 
str : string to be written to the String Buffer.
Return  :
void

• write(String str, int offset, int maxlen) : java.io.StringWriter.write(String str, int offset, int maxlen) escribe una parte de la string en el String Buffer. 
  Sintaxis: 

public void write(String str, int offset, int maxlen)
Parameters : 
str : string to be written to the String Buffer.
offset : start position of the String
maxlen : maximum length upto which string has to written
Return  :
void

• write(char[] carray, int offset, int maxlen) : java.io.StringWriter.write(char[] carray, int offset, int maxlen) escribe una parte de la array de caracteres en el String Buffer. 
  Sintaxis: 

public void write(char[] carray, int offset, int maxlen)
Parameters : 
carray : character to be written to the String Buffer
offset : start position of the character array
maxlen : maximum no. of the character of the carray has to written
Return  :
void

• toString() : java.io.StringWriter.toString() devuelve el valor del búfer de strings como string 
  Sintaxis: 

public String toString()
Parameters : 
-----------
Return  :
string value of the String Buffer

• close() : java.io.StringWriter.close() cierra String Buffer. Dado que el método también se puede llamar después de cerrar el búfer de strings, no juega ningún papel. 
  Sintaxis: 

public void close()
Parameters : 
-----------
Return  :
void

Programa Java que ilustra el uso de los métodos de la clase StringWriter: 

// Java program illustrating the working of StringWriter class methods
// write(int char), write(String str), close()
// write(String str, int offset, int maxlen), toString()
// write(char[] carray, int offset, int maxlen)
 
import java.io.*;
 
public class NewClass
{
    public static void main(String[] args) throws IOException
    {
        // Initializing String Writer
        StringWriter geek_writer1 = new StringWriter();
        StringWriter geek_writer2 = new StringWriter();
        StringWriter geek_writer3 = new StringWriter();
        StringWriter geek_writer4 = new StringWriter();
 
        // Use of write(int char) : to write a character
        geek_writer1.write(71);
        geek_writer1.write(70);
        geek_writer1.write(71);
 
        // Use of toString() : Value written by write(int char)
        System.out.println("Using write(int char) : "+ geek_writer1.toString());
 
        String str = "Hello Geeks";
        // Use of write(String str) : to write string
        geek_writer2.write(str);
 
        // Value written by write(String str)
        System.out.println("Using write(String str) : "+ geek_writer2.toString());
 
        // Use of write(String str, int offset, int maxlen) : to write part of string
        geek_writer3.write(str, 2, 4);
        geek_writer3.write(str, 5, 6);
 
        // Value written by write(String str, int offset, int maxlen)
        System.out.println("Using write(str, offset, maxlen) : "
                                                + geek_writer3.toString());
 
        try
        {
            // Use of Close() method : to close the geek_writer4
            // But no use as String Writer method is still working with it
            geek_writer4.close();
        }
         
        catch (IOException except)
        {
            System.out.println("ERROR");
            except.printStackTrace();;
        }
 
 
        // Initializing character array
        char[] carray = str.toCharArray();
         
        // Use of write(char[] carray, int offset, int maxlen):
        // to write part of char array
        geek_writer4.write(carray, 4, 6);
 
        // Value written by write(String str, int offset, int maxlen)
    System.out.println("Using write(carray, offset, maxlen) : "
                                        + geek_writer4.toString());
 
    }
}

Producción : 

Using write(int char) : GFG
Using write(String str) : Hello Geeks
Using write(str, offset, maxlen) : llo  Geeks
Using write(carray, offset, maxlen) : o Geek

• append(char Sw) : java.io.StringWriter.append(char Sw) agrega un solo carácter al String Buffer. 
  Sintaxis: 

public StringWriter append(char Sw)
Parameters : 
Sw : character to be append
Return  :
StringWriter

• append(CharSequence char_sq) : java.io.StringWriter.append(CharSequence char_sq) agrega la secuencia de caracteres especificada al búfer de strings. 
  Sintaxis: 

public StringWriter append(CharSequence char_sq)
Parameters : 
char_sq : Character sequence to append. 
Return  :
StringWriter, if char sequence is null, then NULL appends to the StringWriter.

• append(CharSequence char_sq, int start, int end) : java.io.StringWriter.append(CharSequence char_sq, int start, int end) añade una parte especificada de una secuencia de caracteres al búfer de strings. 
  Sintaxis: 

public StringWriter append(CharSequence char_sq, int start, int end)
Parameters : 
char_sq : Character sequence to append.
start : start of character in the Char Sequence
end : end of character in the Char Sequence
Return  :
void

• flush() : java.io.StringWriter.flush() vacía el flujo de StringWriter 
  Sintaxis: 

public void flush()
Parameters : 
-----
Return  :
void

• getBuffer() : java.io.StringWriter.getBuffer() devuelve el String Buffer de StringWriter. 
  Sintaxis: 

public StringBuffer getBuffer()
Parameters : 
-----------
Return  :
String Buffer with its current value.

Programa Java que ilustra el uso de los métodos de la clase StringWriter: append(CharSequence char_sq), append(char Sw), append(CharSequence char_sq, int start,int end), flush(), getgetBuffer()

// Java program illustrating the working of StringWriter class methods
// append(CharSequence char_sq), append(char Sw)
// append(CharSequence char_sq, int start,int end)
// flush(), getgetBuffer()
   
import java.io.*;
   
public class NewClass
{
    public static void main(String[] args) throws IOException
    {
        // Initializing String Writer
        StringWriter geek_writer1 = new StringWriter();
        StringWriter geek_writer2 = new StringWriter();
        StringWriter geek_writer3 = new StringWriter();
   
   
        // Use of write(int char) : to write a character
        geek_writer1.write(71);
        geek_writer1.write(70);
        geek_writer1.write(71);
   
   
        // Use of toString() : Value written by write(int char)
        System.out.println("Using write(int char) : "+ geek_writer1.toString());
   
        // Using flush() method
        geek_writer1.flush();
        System.out.println("Using flush() : "+geek_writer1.toString());
   
        // Use of append(char Sw)
        System.out.println("append(char Sw) : " + geek_writer1.append(" 1GFG1"));
   
        // Use of getBuffer() :
        System.out.println("Using geek_writer1 : " + geek_writer1.getBuffer());
   
   
        // Initializing Character Sequence
        CharSequence char_sq1 = "1 Hello 1";
        CharSequence char_sq2 = " : 2 Geeks 2";
   
        // Use of append(CharSequence char_sq)
        geek_writer2.append(char_sq1);
        geek_writer2.append(char_sq2);
   
        System.out.println("append(char_sq) : " + geek_writer2.toString());
   
        // Use of append(CharSequence char_sq,int start,int end)
        geek_writer3.append(char_sq1, 0, 3);
        geek_writer3.append(char_sq2, 3, 6);
   
     System.out.println("append(char_sq,start,end) : " + geek_writer3.toString());
   
    }
}

Producción :

Using write(int char) : GFG
Using flush() : GFG
append(char Sw) : GFG 1GFG1
Using geek_writer1 : GFG 1GFG1
append(char_sq) : 1 Hello 1 : 2 Geeks 2
append(char_sq,start,end) : 1 H2 G

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