A utility class for java

Java Utils

JAVA UTILS

FileUtils.java

class FileUtils {
  
		public static void copyInputStreamToFile( InputStream in, File file ) {
				try {
					OutputStream out = new FileOutputStream(file);
					byte[] buf = new byte[1024];
					int len;
					while((len=in.read(buf))>0){
						out.write(buf,0,len);
					}
					out.close();
					in.close();
				} catch (Exception e) {
						e.printStackTrace();
				}
		}

		public static String safeReadFile(String path, Charset encoding){
			File file                     = new File(path);
			StringBuilder fileContents    = new StringBuilder((int)file.length());
			Scanner scanner               = null;
			String lineSeparator          = System.getProperty("line.separator");

			try {
				scanner = new Scanner(file);
				while(scanner.hasNextLine()) {
					fileContents.append(scanner.nextLine());
					if (scanner.hasNextLine()) {
						fileContents.append(lineSeparator);
					}
				}
				return fileContents.toString();
			}

			catch (FileNotFoundException e) {
				System.out.println("file not found!");
			}

			finally {
				if (scanner != null) {
					scanner.close();
				}
			}

			return null;
		}
		
}

Utils.java

public final class Utils {
	private Utils() { }
	
		// C H E C K E R S
	 
		public static void nonNull(Object object) {
				if (object == null) {
					throw new NullPointerException();
				}
		}
		
		public static void nonNullOfEmpty(Collection<?> collection) {
				if (collection == null) {
					throw new NullPointerException();
				}
				
				if (collection.isEmpty()) {
					throw new IllegalArgumentException();
				}
		}

		public static boolean isNullOrEmpty(String string) {
			return string == null || "".equals(string.trim());
		}

		public static boolean isNullOrEmpty(Collection<?> collection) {
			return collection == null || collection.isEmpty();
		}

	public static boolean isValidEmail(String email) {
	 // email pattern detector - taken from android utils
	 Pattern EMAIL_ADDRESS_PATTERN = Pattern.compile(
				"[a-zA-Z0-9\\+\\.\\_\\%\\-\\+]{1,256}" +
				"\\@" +
				"[a-zA-Z0-9][a-zA-Z0-9\\-]{0,64}" +
				"(" +
				"\\." +
				"[a-zA-Z0-9][a-zA-Z0-9\\-]{0,25}" +
				")+");
				
				
		if (isNullOrEmpty(email)) {
			return false;
		} else {
			return EMAIL_ADDRESS_PATTERN.matcher(email).matches();
		}
	}
}