StringWriter class

See Writer class for descriptions of StringWriter's inherited methods. They are:

.close( ) Closes the stream, flushing it first.

.flush( ) Flushes all associated buffers in a stream without closing it.

.write( int c ) Writes a single char, supplied as the low-order two bytes of a four-byte int.

.write( char[ ] c ) Writes an array of characters.

.write( char[ ] c, int off, int len ) Writes a portion len of a character array, beginning at offset

.write( String s ) Writes a String.

.write( String s, int off, int len ) Writes a portion len of a String, beginning at off

plus:

.getBuffer( ) below

.toString( )

■ Creating “dynamic” Strings. A StringWriter can be used to accumulate characters into a dynamic internal buffer for later manipulation as a familiar String or StringBuffer. This can effectively give you a "dynamic" String to play with, which is not immutable.

■ You can add things to your "dynamic String" using StringWriter's own write( ) methods (above), as the examples of toString( ) and getBuffer( ) below do. Or you can use a PrintWriter, as this next snippet does. i.e. This code prints the following line:

Look at these PrintWriter print results: 55 5.555 0.5 true

import java.io.*;

StringWriter myDynamicString = new StringWriter( );

PrintWriter pw = new PrintWriter( myDynamicString );

// the above statement could be: PrintWriter pw = new PrintWriter( new StringWriter( ); );

pw.print( "Look at these PrintWriter print( ) results: " );

pw.print( 55 + " " );

pw.print( 5.555 + " " );

pw.print( 0.5 + " " );

pw.print( (5 == 5) + " ");

pw.println( );

String s = myDynamicString.toString( );

System.out.print( s );

■ No StringWriter constructors or methods except close( ) throw IOExceptions, although accompanying chained streams may throw them.

■ StringWriter adds two methods to those provided by Writer. They are getBuffer( ) and toString( ). Both are explained below.

String .toString( ) method

■ Returns the contents of the StringWriter as a familiar String. i.e.

import java.io.*;

StringWriter sw = new StringWriter( ); // create a new StringWriter

sw.write( "Hello World" ); // add "Hello World" to it

String s = sw.toString( ); // get it back in a String

System.out.println( s ); // print the String

StringBuffer .getBuffer( ) method

■ Returns the contents of the StringWriter as a familiar StringBuffer. i.e.

import java.io.*;

StringBuffer sb;

StringWriter sw = new StringWriter( ); // create a new StringWriter

sw.write( "Hello " ); // add "Hello" to it

sb = sw.getBuffer( ); // get it back in a StringBuffer

sb.append( "World"); // append "World"

System.out.println( sb ); // print the StringBuffer

■ Combining both approaches from above we have:

import java.io.*;

StringWriter sw = new StringWriter( );

sw.write( "Hello " );

StringBuffer sb = new StringBuffer( sw.toString( ) );

sb.append( "World");

System.out.println( sb );