Thread: i'm new to java. whats is wrong in this code?

OTS.java:

package ots;
 
import java.io.File;
import java.io.IOException;
public class OTS {
 
	public static void main(String[] args) throws IOException {
		CopyDir cp = new CopyDir();
		cp.copyDir(new File(args[0]), new File(args[1]), new File(args[2]));
	}
 
}

CopyDir.java:

package ots;
 
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
 
public class CopyDir {
 
	public CopyDir() {
 
	}
 
	public void copyDir(File sourceLocation, File targetLocation,
			File tempLocation) throws IOException {
 
		if (sourceLocation.isDirectory()) {
			if (!tempLocation.exists()) {
				tempLocation.mkdir();
			}
 
			String[] children = sourceLocation.list();
			for (int i = 0; i < children.length; i++) {
				copyDir(new File(sourceLocation, children[i]), new File(
						tempLocation, children[i]), null);
			}
		} else {
 
			InputStream in = new FileInputStream(sourceLocation);
			OutputStream out = new FileOutputStream(tempLocation);
 
			// Copy the bits from instream to outstream
			byte[] buf = new byte[1024];
			int len;
			while ((len = in.read(buf)) > 0) {
				out.write(buf, 0, len);
			}
			in.close();
			out.close();
		}
		tempLocation.renameTo(targetLocation);
	}
 
}

error:

igor@dual:~$ java -jar ots.jar /home/igor/test /home/igor/123 /home/igor/temp
Exception in thread "main" java.lang.NullPointerException
	at ots.CopyDir.copyDir(CopyDir.java:20)
	at ots.CopyDir.copyDir(CopyDir.java:26)
	at ots.OTS.main(OTS.java:9)

Fixed.

copyDir(new File(sourceLocation, children[i]), new File(
tempLocation, children[i]), null);

changed to:

copyDir(new File(sourceLocation, children[i]), new File(targetLocation, children[i]), new File(
tempLocation, children[i]));