// io/Ex20.java
// TIJ4 Chapter IO, Exercise 20, page 941
// Using Directory.walk() and BinaryFile, verify that all .class files 
// in a directory tree begin with the hex characters 'CAFEBABE'.

/* My solution to one of the exercises in 
* Thinking in Java 4th Edition (by Bruce Eckel).
* It compiles and runs correctly using JDK 1.6.0
* @author Greg Gordon
* @author www.greggordon.org
* March, 2008
*/

import java.io.*;
import net.mindview.util.*;
import static net.mindview.util.BinaryFile.*;
import static org.greggordon.tools.Print.*;

public class Ex20 {
	public static void main(String[] args) throws IOException {
		for(File file : Directory.walk(".", ".*\\.class").files) {
			byte[] ba = read(file);
			for(int i = 0; i < 4; i++)
				print(Integer.toHexString(ba[i] & 0xff).toUpperCase());
			println();
		}		
	} 
}