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. */ package org.apache.commons.lang; import java.math.BigDecimal; import java.math.BigInteger; /** * <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 * @since 1.0 * @version $Id$ * * @deprecated Moved to org.apache.commons.lang.math. * Class will be removed in Commons Lang 3.0. */ public final class NumberUtils { // DEPRECATED CLASS !!! /** * <p><code>NumberUtils</code> instances should NOT be constructed in standard programming. * Instead, the class should be used as <code>NumberUtils.stringToInt("6");</code>.</p> * * <p>This constructor is public to permit tools that require a JavaBean instance * to operate.</p> */ public NumberUtils() { super(); } //-------------------------------------------------------------------- /** * <p>Convert a <code>String</code> to an <code>int</code>, returning * <code>zero</code> if the conversion fails.</p> * * @param str the string to convert * @return the int represented by the string, or <code>zero</code> if * conversion fails */ public static int stringToInt(String str) { return stringToInt(str, 0); } /** * <p>Convert a <code>String</code> to an <code>int</code>, returning a * default value if the conversion fails.</p> * * @param str the string to convert * @param defaultValue the default value * @return the int represented by the string, or the default if conversion fails */ public static int stringToInt(String str, int defaultValue) { try { return Integer.parseInt(str); } catch (NumberFormatException nfe) { return defaultValue; } } //-------------------------------------------------------------------- // must handle Long, Float, Integer, Float, Short, // BigDecimal, BigInteger and Byte // useful methods: // Byte.decode(String) // Byte.valueOf(String,int radix) // Byte.valueOf(String) // Double.valueOf(String) // Float.valueOf(String) // new Float(String) // Integer.valueOf(String,int radix) // Integer.valueOf(String) // Integer.decode(String) // Integer.getInteger(String) // Integer.getInteger(String,int val) // Integer.getInteger(String,Integer val) // new Integer(String) // new Double(String) // new Byte(String) // new Long(String) // Long.getLong(String) // Long.getLong(String,int) // Long.getLong(String,Integer) // Long.valueOf(String,int) // Long.valueOf(String) // new Short(String) // Short.decode(String) // Short.valueOf(String,int) // Short.valueOf(String) // new BigDecimal(String) // new BigInteger(String) // new BigInteger(String,int radix) // Possible inputs: // 45 45.5 45E7 4.5E7 Hex Oct Binary xxxF xxxD xxxf xxxd // plus minus everything. Prolly more. A lot are not separable. /** * <p>Turns a string value into a java.lang.Number.</p> * * <p>First, the value is examined for a type qualifier on the end * (<code>'f','F','d','D','l','L'</code>). If it is found, it starts * trying to create successively larger types from the type specified * until one is found that can hold the value.</p> * * <p>If a type specifier is not found, it will check for a decimal point * and then try successively larger types from <code>Integer</code> to * <code>BigInteger</code> and from <code>Float</code> to * <code>BigDecimal</code>.</p> * * <p>If the string starts with <code>0x</code> or <code>-0x</code>, it * will be interpreted as a hexadecimal integer. Values with leading * <code>0</code>'s will not be interpreted as octal.</p> * * @param val String containing a number * @return Number created from the string * @throws NumberFormatException if the value cannot be converted */ public static Number createNumber(String val) throws NumberFormatException { if (val == null) { return null; } if (val.length() == 0) { throw new NumberFormatException("\"\" is not a valid number."); } if (val.length() == 1 && !Character.isDigit(val.charAt(0))) { throw new NumberFormatException(val + " is not a valid number."); } if (val.startsWith("--")) { // this is protection for poorness in java.lang.BigDecimal. // it accepts this as a legal value, but it does not appear // to be in specification of class. OS X Java parses it to // a wrong value. return null; } if (val.startsWith("0x") || val.startsWith("-0x")) { return createInteger(val); } char lastChar = val.charAt(val.length() - 1); String mant; String dec; String exp; int decPos = val.indexOf('.'); int expPos = val.indexOf('e') + val.indexOf('E') + 1; if (decPos > -1) { if (expPos > -1) { if (expPos < decPos) { throw new NumberFormatException(val + " is not a valid number."); } dec = val.substring(decPos + 1, expPos); } else { dec = val.substring(decPos + 1); } mant = val.substring(0, decPos); } else { if (expPos > -1) { mant = val.substring(0, expPos); } else { mant = val; } dec = null; } if (!Character.isDigit(lastChar)) { if (expPos > -1 && expPos < val.length() - 1) { exp = val.substring(expPos + 1, val.length() - 1); } else { exp = null; } //Requesting a specific type.. String numeric = val.substring(0, val.length() - 1); boolean allZeros = isAllZeros(mant) && isAllZeros(exp); switch (lastChar) { case 'l': case 'L': if (dec == null && exp == null && (numeric.charAt(0) == '-' && isDigits(numeric.substring(1)) || isDigits(numeric))) { try { return createLong(numeric); } catch (NumberFormatException nfe) { //Too big for a long } return createBigInteger(numeric); } throw new NumberFormatException(val + " is not a valid number."); case 'f': case 'F': try { Float f = NumberUtils.createFloat(numeric); if (!(f.isInfinite() || (f.floatValue() == 0.0F && !allZeros))) { //If it's too big for a float or the float value = 0 and the string //has non-zeros in it, then float does not have the precision we want return f; } } catch (NumberFormatException e) { // ignore the bad number } //Fall through case 'd': case 'D': try { Double d = NumberUtils.createDouble(numeric); if (!(d.isInfinite() || (d.floatValue() == 0.0D && !allZeros))) { return d; } } catch (NumberFormatException nfe) { // empty catch } try { return createBigDecimal(numeric); } catch (NumberFormatException e) { // empty catch } //Fall through default: throw new NumberFormatException(val + " is not a valid number."); } } else { //User doesn't have a preference on the return type, so let's start //small and go from there... if (expPos > -1 && expPos < val.length() - 1) { exp = val.substring(expPos + 1, val.length()); } else { exp = null; } if (dec == null && exp == null) { //Must be an int,long,bigint try { return createInteger(val); } catch (NumberFormatException nfe) { // empty catch } try { return createLong(val); } catch (NumberFormatException nfe) { // empty catch } return createBigInteger(val); } else { //Must be a float,double,BigDec boolean allZeros = isAllZeros(mant) && isAllZeros(exp); try { Float f = createFloat(val); if (!(f.isInfinite() || (f.floatValue() == 0.0F && !allZeros))) { return f; } } catch (NumberFormatException nfe) { // empty catch } try { Double d = createDouble(val); if (!(d.isInfinite() || (d.doubleValue() == 0.0D && !allZeros))) { return d; } } catch (NumberFormatException nfe) { // empty catch } return createBigDecimal(val); } } } /** * <p>Utility method for {@link #createNumber(java.lang.String)}.</p> * * <p>Returns <code>true</code> if s is <code>null</code>.</p> * * @param s the String to check * @return if it is all zeros or <code>null</code> */ private static boolean isAllZeros(String s) { if (s == null) { return true; } for (int i = s.length() - 1; i >= 0; i--) { if (s.charAt(i) != '0') { return false; } } return s.length() > 0; } //-------------------------------------------------------------------- /** * <p>Convert a <code>String</code> to a <code>Float</code>.</p> * * @param val a <code>String</code> to convert * @return converted <code>Float</code> * @throws NumberFormatException if the value cannot be converted */ public static Float createFloat(String val) { return Float.valueOf(val); } /** * <p>Convert a <code>String</code> to a <code>Double</code>.</p> * * @param val a <code>String</code> to convert * @return converted <code>Double</code> * @throws NumberFormatException if the value cannot be converted */ public static Double createDouble(String val) { return Double.valueOf(val); } /** * <p>Convert a <code>String</code> to a <code>Integer</code>, handling * hex and octal notations.</p> * * @param val a <code>String</code> to convert * @return converted <code>Integer</code> * @throws NumberFormatException if the value cannot be converted */ public static Integer createInteger(String val) { // decode() handles 0xAABD and 0777 (hex and octal) as well. return Integer.decode(val); } /** * <p>Convert a <code>String</code> to a <code>Long</code>.</p> * * @param val a <code>String</code> to convert * @return converted <code>Long</code> * @throws NumberFormatException if the value cannot be converted */ public static Long createLong(String val) { return Long.valueOf(val); } /** * <p>Convert a <code>String</code> to a <code>BigInteger</code>.</p> * * @param val a <code>String</code> to convert * @return converted <code>BigInteger</code> * @throws NumberFormatException if the value cannot be converted */ public static BigInteger createBigInteger(String val) { BigInteger bi = new BigInteger(val); return bi; } /** * <p>Convert a <code>String</code> to a <code>BigDecimal</code>.</p> * * @param val a <code>String</code> to convert * @return converted <code>BigDecimal</code> * @throws NumberFormatException if the value cannot be converted */ public static BigDecimal createBigDecimal(String val) { BigDecimal bd = new BigDecimal(val); return bd; } //-------------------------------------------------------------------- /** * <p>Gets the minimum of three <code>long</code> values.</p> * * @param a value 1 * @param b value 2 * @param c value 3 * @return the smallest of the values */ public static long minimum(long a, long b, long c) { if (b < a) { a = b; } if (c < a) { a = c; } return a; } /** * <p>Gets the minimum of three <code>int</code> values.</p> * * @param a value 1 * @param b value 2 * @param c value 3 * @return the smallest of the values */ public static int minimum(int a, int b, int c) { if (b < a) { a = b; } if (c < a) { a = c; } return a; } /** * <p>Gets the maximum of three <code>long</code> values.</p> * * @param a value 1 * @param b value 2 * @param c value 3 * @return the largest of the values */ public static long maximum(long a, long b, long c) { if (b > a) { a = b; } if (c > a) { a = c; } return a; } /** * <p>Gets the maximum of three <code>int</code> values.</p> * * @param a value 1 * @param b value 2 * @param c value 3 * @return the largest of the values */ public static int maximum(int a, int b, int c) { if (b > a) { a = b; } if (c > a) { a = c; } return a; } //-------------------------------------------------------------------- /** * <p>Compares two <code>doubles</code> for order.</p> * * <p>This method is more comprehensive than the standard Java greater * than, less than and equals operators.</p> * <ul> * <li>It returns <code>-1</code> if the first value is less than the second. * <li>It returns <code>+1</code> if the first value is greater than the second. * <li>It returns <code>0</code> if the values are equal. * </ul> * * <p> * The ordering is as follows, largest to smallest: * <ul> * <li>NaN * <li>Positive infinity * <li>Maximum double * <li>Normal positive numbers * <li>+0.0 * <li>-0.0 * <li>Normal negative numbers * <li>Minimum double (-Double.MAX_VALUE) * <li>Negative infinity * </ul> * </p> * * <p>Comparing <code>NaN</code> with <code>NaN</code> will * return <code>0</code>.</p> * * @param lhs the first <code>double</code> * @param rhs the second <code>double</code> * @return <code>-1</code> if lhs is less, <code>+1</code> if greater, * <code>0</code> if equal to rhs */ public static int compare(double lhs, double rhs) { if (lhs < rhs) { return -1; } if (lhs > rhs) { return +1; } // Need to compare bits to handle 0.0 == -0.0 being true // compare should put -0.0 < +0.0 // Two NaNs are also == for compare purposes // where NaN == NaN is false long lhsBits = Double.doubleToLongBits(lhs); long rhsBits = Double.doubleToLongBits(rhs); if (lhsBits == rhsBits) { return 0; } // Something exotic! A comparison to NaN or 0.0 vs -0.0 // Fortunately NaN's long is > than everything else // Also negzeros bits < poszero // NAN: 9221120237041090560 // MAX: 9218868437227405311 // NEGZERO: -9223372036854775808 if (lhsBits < rhsBits) { return -1; } else { return +1; } } /** * <p>Compares two floats for order.</p> * * <p>This method is more comprehensive than the standard Java greater than, * less than and equals operators.</p> * <ul> * <li>It returns <code>-1</code> if the first value is less than the second. * <li>It returns <code>+1</code> if the first value is greater than the second. * <li>It returns <code>0</code> if the values are equal. * </ul> * * <p> The ordering is as follows, largest to smallest: * <ul> * <li>NaN * <li>Positive infinity * <li>Maximum float * <li>Normal positive numbers * <li>+0.0 * <li>-0.0 * <li>Normal negative numbers * <li>Minimum float (-Float.MAX_VALUE) * <li>Negative infinity * </ul> * * <p>Comparing <code>NaN</code> with <code>NaN</code> will return * <code>0</code>.</p> * * @param lhs the first <code>float</code> * @param rhs the second <code>float</code> * @return <code>-1</code> if lhs is less, <code>+1</code> if greater, * <code>0</code> if equal to rhs */ public static int compare(float lhs, float rhs) { if (lhs < rhs) { return -1; } if (lhs > rhs) { return +1; } //Need to compare bits to handle 0.0 == -0.0 being true // compare should put -0.0 < +0.0 // Two NaNs are also == for compare purposes // where NaN == NaN is false int lhsBits = Float.floatToIntBits(lhs); int rhsBits = Float.floatToIntBits(rhs); if (lhsBits == rhsBits) { return 0; } //Something exotic! A comparison to NaN or 0.0 vs -0.0 //Fortunately NaN's int is > than everything else //Also negzeros bits < poszero //NAN: 2143289344 //MAX: 2139095039 //NEGZERO: -2147483648 if (lhsBits < rhsBits) { return -1; } else { return +1; } } //-------------------------------------------------------------------- /** * <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 ((str == null) || (str.length() == 0)) { return false; } for (int i = 0; i < str.length(); i++) { if (!Character.isDigit(str.charAt(i))) { return false; } } return true; } /** * <p>Checks whether the String a valid Java number.</p> * * <p>Valid numbers include hexadecimal marked with the <code>0x</code> * qualifier, scientific notation and numbers marked with a type * qualifier (e.g. 123L).</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 the string is a correctly formatted number */ public static boolean isNumber(String str) { if (StringUtils.isEmpty(str)) { return false; } char[] chars = str.toCharArray(); int sz = chars.length; boolean hasExp = false; boolean hasDecPoint = false; boolean allowSigns = false; boolean foundDigit = false; // deal with any possible sign up front int start = (chars[0] == '-') ? 1 : 0; if (sz > start + 1) { if (chars[start] == '0' && chars[start + 1] == 'x') { int i = start + 2; if (i == sz) { return false; // str == "0x" } // checking hex (it can't be anything else) for (; i < chars.length; i++) { if ((chars[i] < '0' || chars[i] > '9') && (chars[i] < 'a' || chars[i] > 'f') && (chars[i] < 'A' || chars[i] > 'F')) { return false; } } return true; } } sz--; // don't want to loop to the last char, check it afterwords // for type qualifiers int i = start; // loop to the next to last char or to the last char if we need another digit to // make a valid number (e.g. chars[0..5] = "1234E") while (i < sz || (i < sz + 1 && allowSigns && !foundDigit)) { if (chars[i] >= '0' && chars[i] <= '9') { foundDigit = true; allowSigns = false; } else if (chars[i] == '.') { if (hasDecPoint || hasExp) { // two decimal points or dec in exponent return false; } hasDecPoint = true; } else if (chars[i] == 'e' || chars[i] == 'E') { // we've already taken care of hex. if (hasExp) { // two E's return false; } if (!foundDigit) { return false; } hasExp = true; allowSigns = true; } else if (chars[i] == '+' || chars[i] == '-') { if (!allowSigns) { return false; } allowSigns = false; foundDigit = false; // we need a digit after the E } else { return false; } i++; } if (i < chars.length) { if (chars[i] >= '0' && chars[i] <= '9') { // no type qualifier, OK return true; } if (chars[i] == 'e' || chars[i] == 'E') { // can't have an E at the last byte return false; } if (!allowSigns && (chars[i] == 'd' || chars[i] == 'D' || chars[i] == 'f' || chars[i] == 'F')) { return foundDigit; } if (chars[i] == 'l' || chars[i] == 'L') { // not allowing L with an exponent return foundDigit && !hasExp; } // last character is illegal return false; } // allowSigns is true iff the val ends in 'E' // found digit it to make sure weird stuff like '.' and '1E-' doesn't pass return !allowSigns && foundDigit; } }