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

  1. #1
    Junior Member
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    Default 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)


  2. #2
    Junior Member
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    Default Re: i'm new to java. whats is wrong in this code?

    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]));

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