Java tutorial
/* * Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You under the Apache License, Version 2.0 * (the "License"); you may not use this file except in compliance with * the License. You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ /** * <p>Provides extra functionality for Java Number classes.</p> * * @author <a href="mailto:rand_mcneely@yahoo.com">Rand McNeely</a> * @author Stephen Colebourne * @author <a href="mailto:steve.downey@netfolio.com">Steve Downey</a> * @author Eric Pugh * @author Phil Steitz * @author Matthew Hawthorne * @author <a href="mailto:ggregory@seagullsw.com">Gary Gregory</a> * @author <a href="mailto:fredrik@westermarck.com">Fredrik Westermarck</a> * @since 2.0 * @version $Id: NumberUtils.java 609475 2008-01-06 23:58:59Z bayard $ */ public class Main { /** * <p>Checks whether the <code>String</code> contains only * digit characters.</p> * * <p><code>Null</code> and empty String will return * <code>false</code>.</p> * * @param str the <code>String</code> to check * @return <code>true</code> if str contains only unicode numeric */ public static boolean isDigits(String str) { if (isEmpty(str)) { return false; } for (int i = 0; i < str.length(); i++) { if (!Character.isDigit(str.charAt(i))) { return false; } } return true; } // Empty checks //----------------------------------------------------------------------- /** * <p>Checks if a String is empty ("") or null.</p> * * <pre> * StringUtils.isEmpty(null) = true * StringUtils.isEmpty("") = true * StringUtils.isEmpty(" ") = false * StringUtils.isEmpty("bob") = false * StringUtils.isEmpty(" bob ") = false * </pre> * * <p>NOTE: This method changed in Lang version 2.0. * It no longer trims the String. * That functionality is available in isBlank().</p> * * @param str the String to check, may be null * @return <code>true</code> if the String is empty or null */ public static boolean isEmpty(String str) { return str == null || str.length() == 0; } }