Java StringWriter class

In this tutorial, we will learn about Java StringWriter and its subclasses with the help of examples.

The StringWriter class in the java.io package can be used to write data (in characters) to the string buffer.

It inherits the abstract class Writer.

NoteIn Java, string buffers are considered mutable strings. That is, we can modify the string buffer. To convert the string buffer to a string, we can use the toString() method.

Create a StringWriter

To create a StringWriter, we must first import the java.io.StringWriter package. After importing the package, we can create the string writer.

//Create StringWriter
StringWriter output = new StringWriter();

Here, we created a string writer with the default string buffer capacity. However, we can also specify the capacity of the string buffer.

//Create a StringWriter with a specified string buffer capacity
StringWriter output = new StringWriter(int size);

Here, size specifies the capacity of the string buffer.

StringWriter methods

The StringWriter class provides implementations for different methods provided by the Writer class.

write() method

• write() - Write a character to the string writer

• write(char[] array) - Write the characters in the specified array to the writer

• write(String data) - Write the specified string to the writer

Example: Java StringWriter

import java.io.StringWriter;
public class Main {
　　public static void main(String[] args) {
　　　　String data = "This is the text in the string.";
　　　　try {
　　　　　　//Create a StringWriter with a default string buffer capacity
　　　　　　StringWriter output = new StringWriter();
　　　　　　//Write data to the string buffer
　　　　　　output.write(data);
　　　　　　//Print StringWriter
　　　　　　System.out.println("Data in StringWriter: "　+　output);
　　　　　　output.close();
　　　　}
　　　　catch(Exception　e)　{
　　　　　　e.getStackTrace();
　　　　}
　　}
}

Output Result

Data in StringWriter: This is the text in the string.

In the above example, we created a string writer named output.

StringWriter output = new StringWriter();

Then, we use the write() method to write string data into the string buffer.

Note: We have used the toString() method to obtain the output data in string form from the string buffer.

Access data from StringBuffer

• getBuffer() -Return the existing data in the string buffer

• toString() -Return the existing data in the string buffer as a string

For example

import java.io.StringWriter;
public class Main {
　　public static void main(String[] args) {
　　　　String data = "This is the original data";
　　　　try {
　　　　　　//Create a StringWriter with a default string buffer capacity
　　　　　　StringWriter output = new StringWriter();
　　　　　　//Write data to the string buffer
　　　　　　output.write(data);
　　　　　　//Return the string buffer
　　　　　　StringBuffer stringBuffer = output.getBuffer();
　　　　　　System.out.println("StringBuffer: "　+　stringBuffer);
　　　　　　//Return the string buffer as a string
　　　　　　String string = output.toString();
　　　　　　System.out.println("String: "　+　string);
　　　　　　output.close();
　　　　}
　　　　catch(Exception　e)　{
　　　　　　e.getStackTrace();
　　　　}
　　}
}

Output Result

StringBuffer:　This　is　the　original　data
String:　This　is　the　original　data

Here, we use the getBuffer() method to get the data existing in the string buffer. And the toString() method also returns the data existing in the string buffer in string form.

close() Method

To close the string writer, we can use the close() method.

However, the close() method is invalid in the StringWriter class. Even if the close() method is called, we can still use the methods of this class.

Other Methods of StringWriter