Check if string exists - Procyon

Well, I'm trying to make a program that reads the code from a .class file, decompile it, and check for a string there. I'm using the Procyon library, but I do not know how.

This is my code to decompile the file:

import java.io.PrintWriter;

public class Main {
    public static void main(String[] args) {
        final PrintWriter writer = new PrintWriter(System.out);
        try {
            com.strobel.decompiler.Decompiler.decompile(
                "C:\codigo.class",
                new com.strobel.decompiler.PlainTextOutput(writer)
            );
        }
        finally {
            writer.flush();
        }
    }
}