Java Appendable Interface

Introduction

The Appendable interface in Java provides a standard way to append character sequences and values to a destination, such as a StringBuilder or Writer. It is used in various classes to allow appending operations.

Appendable interface located in java.lang package.

Table of Contents

1. What is Appendable?
2. Key Methods
3. Implementations
4. Examples of Appendable
5. Conclusion

1. What is Appendable?

Appendable is an interface that defines methods for appending characters or sequences to objects. It provides a flexible way to accumulate text.

2. Key Methods

• append(CharSequence csq): Appends the specified character sequence.
• append(CharSequence csq, int start, int end): Appends a subsequence of the specified character sequence.
• append(char c): Appends a single character.

3. Implementations

Common classes that implement Appendable include:

• StringBuilder
• StringBuffer
• Writer and its subclasses, such as FileWriter and PrintWriter

4. Examples of Appendable

Example 1: Using Appendable with StringBuilder

This example demonstrates how to use Appendable methods with StringBuilder.

import java.io.IOException;

public class AppendableExample {
    public static void main(String[] args) {
        Appendable appendable = new StringBuilder();

        try {
            appendable.append("Hello, ");
            appendable.append("World!");
            appendable.append('\n');
            appendable.append("Welcome to Java.");
            System.out.println(appendable.toString());
        } catch (IOException e) {
            System.out.println("Error: " + e.getMessage());
        }
    }
}

Output:

Hello, World!
Welcome to Java.

Example 2: Appending a Subsequence

Here, we append a subsequence of a character sequence using append(CharSequence csq, int start, int end).

import java.io.IOException;

public class AppendSubsequenceExample {
    public static void main(String[] args) {
        Appendable appendable = new StringBuilder();
        CharSequence text = "Hello, World!";

        try {
            appendable.append(text, 7, 12); // Appends "World"
            System.out.println(appendable.toString());
        } catch (IOException e) {
            System.out.println("Error: " + e.getMessage());
        }
    }
}

Output:

World

Example 3: Using Appendable with Writer

This example shows how to use Appendable methods with a Writer.

import java.io.FileWriter;
import java.io.IOException;
import java.io.Writer;

public class WriterAppendableExample {
    public static void main(String[] args) {
        try (Writer writer = new FileWriter("output.txt")) {
            Appendable appendable = writer;
            appendable.append("Hello, File!");
            appendable.append('\n');
            appendable.append("Appending text to a file.");
            writer.flush();
            System.out.println("Text written to file.");
        } catch (IOException e) {
            System.out.println("Error: " + e.getMessage());
        }
    }
}

Output:

Text written to file.

Conclusion

The Appendable interface in Java provides a standard way to append character sequences and values to objects. It is implemented by various classes like StringBuilder, StringBuffer, and Writer, making it a flexible tool for text accumulation and manipulation in Java applications.