Java tutorial
//package com.java2s; /* * 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. */ public class Main { /** * <p>Converts the character to the Integer it represents, throwing an * exception if the character is not numeric.</p> * * <p>This method coverts the char '1' to the int 1 and so on.</p> * * <pre> * CharUtils.toIntValue('3') = 3 * CharUtils.toIntValue('A') throws IllegalArgumentException * </pre> * * @param ch the character to convert * @return the int value of the character * @throws IllegalArgumentException if the character is not ASCII numeric */ public static int toIntValue(final char ch) { if (isAsciiNumeric(ch) == false) { throw new IllegalArgumentException("The character " + ch + " is not in the range '0' - '9'"); } return ch - 48; } /** * <p>Converts the character to the Integer it represents, throwing an * exception if the character is not numeric.</p> * * <p>This method coverts the char '1' to the int 1 and so on.</p> * * <pre> * CharUtils.toIntValue('3', -1) = 3 * CharUtils.toIntValue('A', -1) = -1 * </pre> * * @param ch the character to convert * @param defaultValue the default value to use if the character is not numeric * @return the int value of the character */ public static int toIntValue(final char ch, final int defaultValue) { if (isAsciiNumeric(ch) == false) { return defaultValue; } return ch - 48; } /** * <p>Converts the character to the Integer it represents, throwing an * exception if the character is not numeric.</p> * * <p>This method coverts the char '1' to the int 1 and so on.</p> * * <pre> * CharUtils.toIntValue('3') = 3 * CharUtils.toIntValue(null) throws IllegalArgumentException * CharUtils.toIntValue('A') throws IllegalArgumentException * </pre> * * @param ch the character to convert, not null * @return the int value of the character * @throws IllegalArgumentException if the Character is not ASCII numeric or is null */ public static int toIntValue(final Character ch) { if (ch == null) { throw new IllegalArgumentException("The character must not be null"); } return toIntValue(ch.charValue()); } /** * <p>Converts the character to the Integer it represents, throwing an * exception if the character is not numeric.</p> * * <p>This method coverts the char '1' to the int 1 and so on.</p> * * <pre> * CharUtils.toIntValue(null, -1) = -1 * CharUtils.toIntValue('3', -1) = 3 * CharUtils.toIntValue('A', -1) = -1 * </pre> * * @param ch the character to convert * @param defaultValue the default value to use if the character is not numeric * @return the int value of the character */ public static int toIntValue(final Character ch, final int defaultValue) { if (ch == null) { return defaultValue; } return toIntValue(ch.charValue(), defaultValue); } /** * <p>Checks whether the character is ASCII 7 bit numeric.</p> * * <pre> * CharUtils.isAsciiNumeric('a') = false * CharUtils.isAsciiNumeric('A') = false * CharUtils.isAsciiNumeric('3') = true * CharUtils.isAsciiNumeric('-') = false * CharUtils.isAsciiNumeric('\n') = false * CharUtils.isAsciiNumeric('©') = false * </pre> * * @param ch the character to check * @return true if between 48 and 57 inclusive */ public static boolean isAsciiNumeric(final char ch) { return ch >= '0' && ch <= '9'; } }