decompile a .class file programmatically

I am currently working on a project which demands me to decompile a .class file to java file programmatically. I.E. I have a program that should read a class file and decompile it and the resultant java source code is written into a file. Please help me out to do it.
EDIT: I am completely new to the world of decompilers. I have gone through a few APIs, but i don't know precisely how to use and which one to use. Any sort of help will be really appreciable
EDIT:
I tried using:

import com.strobel.decompiler.*;
import java.io.*;
public class JavaDecode {

   public static void main(String[] args)throws Exception {
      decompileee();
   }

   private static void decompileee()throws Exception{
      final DecompilerSettings settings = DecompilerSettings.javaDefaults();
      final FileOutputStream stream = new FileOutputStream("C:/jp/decompiled.java");
      final OutputStreamWriter writer = new OutputStreamWriter(stream); 
      Decompiler.decompile("C:/jp/X.class", new PlainTextOutput(writer),settings);
      System.out.println("Success");
   }
}

But the above code simply created a file called "decompiled.java" in the scpecified directory. But the file is an empty file.

Procyon includes a Java decompiler framework. It's written in Java, and it can be called as a library. There's not much documentation yet, but I am the author, and I can assist you if you run into trouble--just contact me on BitBucket.

A simple example of how to decompile java.lang.String:

final DecompilerSettings settings = DecompilerSettings.javaDefaults();

try (final FileOutputStream stream = new FileOutputStream("path/to/file");
     final OutputStreamWriter writer = new OutputStreamWriter(stream)) {

    Decompiler.decompile(
        "java.lang.String",
        new PlainTextOutput(writer),
        settings
    );
}
catch (final IOException e) {
    // handle error
}

You can also pass a .class file path to the decompile() method instead of a class name.

If you're not using Java 7, make sure to flush/close your I/O resources manually, e.g.:

try {
    final FileOutputStream stream = new FileOutputStream("path/to/file");

    try {
        final OutputStreamWriter writer = new OutputStreamWriter(stream);

        try {
            Decompiler.decompile(
                "java.lang.String",
                new PlainTextOutput(writer),
                DecompilerSettings.javaDefaults()
            );
        }
        finally {
            writer.close();
        }
    }
    finally {
        stream.close();
    }
}
catch (final IOException e) {
    // handle error
}