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NumberUtils源码分析

發(fā)布時(shí)間：2025/3/21 编程问答 21 豆豆

生活随笔收集整理的這篇文章主要介紹了 NumberUtils源码分析小編覺得挺不錯(cuò)的,現(xiàn)在分享給大家,幫大家做個(gè)參考.

NumberUtils類介紹

org.apache.commons.lang3.math.NumberUtils?類是org.apache.commons包下的一個(gè)工具類，主要功能入類名描述的一樣。數(shù)字工具類。?

運(yùn)行環(huán)境

OS:Win7 64bit
idea:IntelliJ IDEA 2017
jdkVersion:1.7.0_79 64 bit
使用的pom.xml

<dependency><groupId>org.apache.commons</groupId><artifactId>commons-lang3</artifactId><version>3.6</version></dependency>

NumberUtils 源碼解析

NumberUtils源碼如下：

package org.apache.commons.lang3.math;import java.lang.reflect.Array; import java.math.BigDecimal; import java.math.BigInteger;import org.apache.commons.lang3.StringUtils; import org.apache.commons.lang3.SystemUtils; import org.apache.commons.lang3.Validate;/*** <p>Provides extra functionality for Java Number classes.</p>** @since 2.0*/ public class NumberUtils {/** 可重復(fù)使用的Long常量0L */public static final Long LONG_ZERO = Long.valueOf(0L);/** 可重復(fù)使用的Long常量1L */public static final Long LONG_ONE = Long.valueOf(1L);/** 可重復(fù)使用的Long常量-1L */public static final Long LONG_MINUS_ONE = Long.valueOf(-1L);/** 可重復(fù)使用的Integer常量0 */public static final Integer INTEGER_ZERO = Integer.valueOf(0);/** 可重復(fù)使用的Integer常量1 */public static final Integer INTEGER_ONE = Integer.valueOf(1);/** 可重復(fù)使用的Integer常量-1 */public static final Integer INTEGER_MINUS_ONE = Integer.valueOf(-1);/** 可重復(fù)使用的Short常量0 */public static final Short SHORT_ZERO = Short.valueOf((short) 0);/** 可重復(fù)使用的Short常量1 */public static final Short SHORT_ONE = Short.valueOf((short) 1);/** 可重復(fù)使用的Short常量-1 */public static final Short SHORT_MINUS_ONE = Short.valueOf((short) -1);/** 可重復(fù)使用的Byte常量0 */public static final Byte BYTE_ZERO = Byte.valueOf((byte) 0);/** 可重復(fù)使用的Byte常量1 */public static final Byte BYTE_ONE = Byte.valueOf((byte) 1);/** 可重復(fù)使用的Byte常量-1 */public static final Byte BYTE_MINUS_ONE = Byte.valueOf((byte) -1);/** 可重復(fù)使用的Double常量0.0d */public static final Double DOUBLE_ZERO = Double.valueOf(0.0d);/** 可重復(fù)使用的Double常量1.0d */public static final Double DOUBLE_ONE = Double.valueOf(1.0d);/** 可重復(fù)使用的Double常量-1.0d */public static final Double DOUBLE_MINUS_ONE = Double.valueOf(-1.0d);/** 可重復(fù)使用的Float常量0.0f */public static final Float FLOAT_ZERO = Float.valueOf(0.0f);/** 可重復(fù)使用的Float常量1.0f */public static final Float FLOAT_ONE = Float.valueOf(1.0f);/** 可重復(fù)使用的Float常量-1.0f */public static final Float FLOAT_MINUS_ONE = Float.valueOf(-1.0f);/*** 我們使用的時(shí)候無需創(chuàng)建該工具類，像這樣使用 NumberUtils.toInt("6");* 該構(gòu)造方法是為了符合JavaBean的規(guī)范*/public NumberUtils() {super();}//-----------------------------------------------------------------------/***轉(zhuǎn)換str為int,如果轉(zhuǎn)換失敗則返回0 **/public static int toInt(final String str) {return toInt(str, 0);}/***轉(zhuǎn)換str為int，如果轉(zhuǎn)換失敗則返回defaultValue**/public static int toInt(final String str, final int defaultValue) {if(str == null) {return defaultValue;}try {return Integer.parseInt(str);} catch (final NumberFormatException nfe) {return defaultValue;}}/***轉(zhuǎn)換str為long，如果轉(zhuǎn)換失敗則返回0L**/public static long toLong(final String str) {return toLong(str, 0L);}/***轉(zhuǎn)換str為long，如果轉(zhuǎn)換失敗則返回defaultValue**/public static long toLong(final String str, final long defaultValue) {if (str == null) {return defaultValue;}try {return Long.parseLong(str);} catch (final NumberFormatException nfe) {return defaultValue;}}/***轉(zhuǎn)換str為float，如果轉(zhuǎn)換失敗則返回0.0f**/public static float toFloat(final String str) {return toFloat(str, 0.0f);}/***轉(zhuǎn)換str為float，如果轉(zhuǎn)換失敗則返回defaultValue*/public static float toFloat(final String str, final float defaultValue) {if (str == null) {return defaultValue;}try {return Float.parseFloat(str);} catch (final NumberFormatException nfe) {return defaultValue;}}/***轉(zhuǎn)換str為double，如果轉(zhuǎn)換失敗則返回0.0d*/public static double toDouble(final String str) {return toDouble(str, 0.0d);}/***轉(zhuǎn)換str為double，如果轉(zhuǎn)換失敗則返回defaultValue*/public static double toDouble(final String str, final double defaultValue) {if (str == null) {return defaultValue;}try {return Double.parseDouble(str);} catch (final NumberFormatException nfe) {return defaultValue;}}/***轉(zhuǎn)換str為byte，如果轉(zhuǎn)換失敗則返回0*/public static byte toByte(final String str) {return toByte(str, (byte) 0);}/***轉(zhuǎn)換str為byte，如果轉(zhuǎn)換失敗則返回defaultValue*/public static byte toByte(final String str, final byte defaultValue) {if(str == null) {return defaultValue;}try {return Byte.parseByte(str);} catch (final NumberFormatException nfe) {return defaultValue;}}/***轉(zhuǎn)換str為short，如果轉(zhuǎn)換失敗則返回0*/public static short toShort(final String str) {return toShort(str, (short) 0);}/***轉(zhuǎn)換str為short，如果轉(zhuǎn)換失敗則返回defaultValue*/public static short toShort(final String str, final short defaultValue) {if(str == null) {return defaultValue;}try {return Short.parseShort(str);} catch (final NumberFormatException nfe) {return defaultValue;}}/*** 將一個(gè)String的值轉(zhuǎn)換為java.lang.Number* 如果這個(gè)字符串以0x、0X、-0x、-0X、#、-#開始，這個(gè)字符將轉(zhuǎn)換成 hexadecimal Integer類型，如果前綴后面的數(shù)字超過8個(gè)則轉(zhuǎn)換成Long類型* 如果超過16個(gè)則轉(zhuǎn)換成BIgInteger。* 還會檢查這個(gè)值是否是以預(yù)定義的字符結(jié)束，例如'f','F','d','D','l','L'.如果找到對應(yīng)的，將開始依次創(chuàng)建較大的類型直到找到能匹配這個(gè)值的類型。* 如果沒有找到類型標(biāo)識符，將作為小數(shù)進(jìn)行驗(yàn)證并且是依次從Intger到BigInteger，Float 到BigDecimal。* 0開頭的數(shù)字將作為八進(jìn)制轉(zhuǎn)換，返回的數(shù)字是相應(yīng)的Integer，Long 或BigDecimal * 如果參數(shù)為空則返回null* 這個(gè)方法不會對參數(shù)進(jìn)行trim操作，如果頭部或尾部有空格的話將會生成NumberFormatExceptions* */public static Number createNumber(final String str) throws NumberFormatException {if (str == null) {return null;}if (StringUtils.isBlank(str)) {throw new NumberFormatException("A blank string is not a valid number");}// Need to deal with all possible hex prefixes herefinal String[] hex_prefixes = {"0x", "0X", "-0x", "-0X", "#", "-#"};int pfxLen = 0;for(final String pfx : hex_prefixes) {if (str.startsWith(pfx)) {pfxLen += pfx.length();break;}}if (pfxLen > 0) { // 是十六進(jìn)制 we have a hex numberchar firstSigDigit = 0; // 去掉開頭的0 strip leading zeroesfor(int i = pfxLen; i < str.length(); i++) {firstSigDigit = str.charAt(i);if (firstSigDigit == '0') { // 統(tǒng)計(jì)有多少個(gè)0開頭 count leading zeroespfxLen++;} else {break;}}final int hexDigits = str.length() - pfxLen; //計(jì)算不包含0的數(shù)字的長度if (hexDigits > 16 || hexDigits == 16 && firstSigDigit > '7') { // 使用BigIntegerreturn createBigInteger(str);}if (hexDigits > 8 || hexDigits == 8 && firstSigDigit > '7') { // 使用Longreturn createLong(str);}return createInteger(str);}final char lastChar = str.charAt(str.length() - 1); //獲取最后一個(gè)數(shù)字String mant;String dec;String exp;final int decPos = str.indexOf('.');final int expPos = str.indexOf('e') + str.indexOf('E') + 1; // assumes both not present// if both e and E are present, this is caught by the checks on expPos (which prevent IOOBE)// and the parsing which will detect if e or E appear in a number due to using the wrong offsetif (decPos > -1) { // 這個(gè)是一個(gè)小數(shù)數(shù)字 there is a decimal pointif (expPos > -1) { // 這是一個(gè)指數(shù) there is an exponentif (expPos < decPos || expPos > str.length()) { // 防止雙指數(shù)導(dǎo)致IOOBE prevents double exponent causing IOOBEthrow new NumberFormatException(str + " is not a valid number.");}dec = str.substring(decPos + 1, expPos);} else {dec = str.substring(decPos + 1);}mant = getMantissa(str, decPos);} else {if (expPos > -1) {if (expPos > str.length()) { // 防止雙指數(shù)導(dǎo)致IOOBE prevents double exponent causing IOOBEthrow new NumberFormatException(str + " is not a valid number.");}mant = getMantissa(str, expPos);} else {mant = getMantissa(str);}dec = null;}if (!Character.isDigit(lastChar) && lastChar != '.') {if (expPos > -1 && expPos < str.length() - 1) {exp = str.substring(expPos + 1, str.length() - 1);} else {exp = null;}//Requesting a specific type.. 是否是特定的類型final String numeric = str.substring(0, str.length() - 1);final 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 (final NumberFormatException nfe) { // NOPMD// Too big for a long}return createBigInteger(numeric);}throw new NumberFormatException(str + " is not a valid number.");case 'f' :case 'F' :try {final Float f = NumberUtils.createFloat(str);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 wantreturn f;}} catch (final NumberFormatException nfe) { // NOPMD// ignore the bad number}//$FALL-THROUGH$case 'd' :case 'D' :try {final Double d = NumberUtils.createDouble(str);if (!(d.isInfinite() || d.floatValue() == 0.0D && !allZeros)) {return d;}} catch (final NumberFormatException nfe) { // NOPMD// ignore the bad number}try {return createBigDecimal(numeric);} catch (final NumberFormatException e) { // NOPMD// ignore the bad number}//$FALL-THROUGH$default :throw new NumberFormatException(str + " is not a valid number.");}}//User doesn't have a preference on the return type, so let's start//small and go from there...//不屬于任何類型if (expPos > -1 && expPos < str.length() - 1) {exp = str.substring(expPos + 1, str.length());} else {exp = null;}if (dec == null && exp == null) { // no decimal point and no exponent//Must be an Integer, Long, Bigintegertry {return createInteger(str);} catch (final NumberFormatException nfe) { // NOPMD// ignore the bad number}try {return createLong(str);} catch (final NumberFormatException nfe) { // NOPMD// ignore the bad number}return createBigInteger(str);}//Must be a Float, Double, BigDecimal//也許是Float，Double，BigDecimalfinal boolean allZeros = isAllZeros(mant) && isAllZeros(exp);try {final Float f = createFloat(str);final Double d = createDouble(str);if (!f.isInfinite()&& !(f.floatValue() == 0.0F && !allZeros)&& f.toString().equals(d.toString())) {return f;}if (!d.isInfinite() && !(d.doubleValue() == 0.0D && !allZeros)) {final BigDecimal b = createBigDecimal(str);if (b.compareTo(BigDecimal.valueOf(d.doubleValue())) == 0) {return d;}return b;}} catch (final NumberFormatException nfe) { // NOPMD// ignore the bad number}return createBigDecimal(str);}/*** createNumber()方法使用* 獲取尾數(shù)的，也就是返回不包括符號位的數(shù)字*/private static String getMantissa(final String str) {return getMantissa(str, str.length());}/*** createNumber()方法使用* 獲取尾數(shù)的，也就是返回不包括符號位的數(shù)字可以指定獲取長度*/private static String getMantissa(final String str, final int stopPos) {final char firstChar = str.charAt(0);final boolean hasSign = firstChar == '-' || firstChar == '+';return hasSign ? str.substring(1, stopPos) : str.substring(0, stopPos);}/*** createNumber()方法使用* 如果字符串為空返回true，如果字符串中的沒有等于0的返回true*/private static boolean isAllZeros(final String str) {if (str == null) {return true;}for (int i = str.length() - 1; i >= 0; i--) {if (str.charAt(i) != '0') {return false;}}return str.length() > 0;}//-----------------------------------------------------------------------/*** 轉(zhuǎn)換String為Float* 如果String為空則返回null*/public static Float createFloat(final String str) {if (str == null) {return null;}return Float.valueOf(str);}/*** 轉(zhuǎn)換String為Double* 如果String為空則返回null*/public static Double createDouble(final String str) {if (str == null) {return null;}return Double.valueOf(str);}/*** 轉(zhuǎn)換String為Integer，處理hex和octal進(jìn)制。* 注意0開頭表示octal進(jìn)制，不會進(jìn)行trim操作*/public static Integer createInteger(final String str) {if (str == null) {return null;}// decode() handles 0xAABD and 0777 (hex and octal) as well.return Integer.decode(str);}/*** 轉(zhuǎn)換String為Long，處理hex和octal進(jìn)制。* 注意0開頭表示octal進(jìn)制，不會進(jìn)行trim操作*/public static Long createLong(final String str) {if (str == null) {return null;}return Long.decode(str);}/*** 轉(zhuǎn)換String為BigInteger* 從3.2版本后可以處理hex(0x or #開頭)和octal (0開頭)進(jìn)制* 字符串為null返回null */public static BigInteger createBigInteger(final String str) {if (str == null) {return null;}int pos = 0; // offset within stringint radix = 10;boolean negate = false; // need to negate later?if (str.startsWith("-")) {negate = true;pos = 1;}if (str.startsWith("0x", pos) || str.startsWith("0X", pos)) { // hexradix = 16;pos += 2;} else if (str.startsWith("#", pos)) { // alternative hex (allowed by Long/Integer)radix = 16;pos ++;} else if (str.startsWith("0", pos) && str.length() > pos + 1) { // octal; so long as there are additional digitsradix = 8;pos ++;} // default is to treat as decimalfinal BigInteger value = new BigInteger(str.substring(pos), radix);return negate ? value.negate() : value;}/*** 轉(zhuǎn)換String為Double* 如果String為空則返回null*/public static BigDecimal createBigDecimal(final String str) {if (str == null) {return null;}// handle JDK1.3.1 bug where "" throws IndexOutOfBoundsExceptionif (StringUtils.isBlank(str)) {throw new NumberFormatException("A blank string is not a valid number");}if (str.trim().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.throw new NumberFormatException(str + " is not a valid number.");}return new BigDecimal(str);}// Min in array//--------------------------------------------------------------------/*** 返回?cái)?shù)組的最小值*/public static long min(final long... array) {// Validates inputvalidateArray(array);// Finds and returns minlong min = array[0];for (int i = 1; i < array.length; i++) {if (array[i] < min) {min = array[i];}}return min;}/*** 返回?cái)?shù)組中最小的* 從3.4版本后修改方法簽名 min(int[]) to min(int...)*/public static int min(final int... array) {// Validates inputvalidateArray(array);// Finds and returns minint min = array[0];for (int j = 1; j < array.length; j++) {if (array[j] < min) {min = array[j];}}return min;}/*** 返回?cái)?shù)組中最小的* 從3.4版本后修改方法簽名 min(short[]) to min(short...)*/public static short min(final short... array) {// Validates inputvalidateArray(array);// Finds and returns minshort min = array[0];for (int i = 1; i < array.length; i++) {if (array[i] < min) {min = array[i];}}return min;}/*** 返回?cái)?shù)組中最小的* 從3.4版本后修改方法簽名 min(byte[]) to min(byte...)*/public static byte min(final byte... array) {// Validates inputvalidateArray(array);// Finds and returns minbyte min = array[0];for (int i = 1; i < array.length; i++) {if (array[i] < min) {min = array[i];}}return min;}/*** 返回?cái)?shù)組中最小的* 從3.4版本后修改方法簽名 min(double[]) to min(double...)*/public static double min(final double... array) {// Validates inputvalidateArray(array);// Finds and returns mindouble min = array[0];for (int i = 1; i < array.length; i++) {if (Double.isNaN(array[i])) {return Double.NaN;}if (array[i] < min) {min = array[i];}}return min;}/*** 返回?cái)?shù)組中最小的* 從3.4版本后修改方法簽名 min(float[]) to min(float...)*/public static float min(final float... array) {// Validates inputvalidateArray(array);// Finds and returns minfloat min = array[0];for (int i = 1; i < array.length; i++) {if (Float.isNaN(array[i])) {return Float.NaN;}if (array[i] < min) {min = array[i];}}return min;}// Max in array//--------------------------------------------------------------------/*** 返回?cái)?shù)組中最大的* 從3.4版本后修改方法簽名 min(long[]) to min(long...)*/public static long max(final long... array) {// Validates inputvalidateArray(array);// Finds and returns maxlong max = array[0];for (int j = 1; j < array.length; j++) {if (array[j] > max) {max = array[j];}}return max;}/*** 返回?cái)?shù)組中最大的* 從3.4版本后修改方法簽名 min(int[]) to min(int...)*/public static int max(final int... array) {// Validates inputvalidateArray(array);// Finds and returns maxint max = array[0];for (int j = 1; j < array.length; j++) {if (array[j] > max) {max = array[j];}}return max;}/*** 返回?cái)?shù)組中最大的* 從3.4版本后修改方法簽名 min(short[]) to min(short...)*/public static short max(final short... array) {// Validates inputvalidateArray(array);// Finds and returns maxshort max = array[0];for (int i = 1; i < array.length; i++) {if (array[i] > max) {max = array[i];}}return max;}/*** 返回?cái)?shù)組中最大的* 從3.4版本后修改方法簽名 min(byte[]) to min(byte...)*/public static byte max(final byte... array) {// Validates inputvalidateArray(array);// Finds and returns maxbyte max = array[0];for (int i = 1; i < array.length; i++) {if (array[i] > max) {max = array[i];}}return max;}/*** 返回?cái)?shù)組中最大的* 從3.4版本后修改方法簽名 min(double[]) to min(double...)*/public static double max(final double... array) {// Validates inputvalidateArray(array);// Finds and returns maxdouble max = array[0];for (int j = 1; j < array.length; j++) {if (Double.isNaN(array[j])) {return Double.NaN;}if (array[j] > max) {max = array[j];}}return max;}/*** 返回?cái)?shù)組中最大的* 從3.4版本后修改方法簽名 min(float[]) to min(float...)*/public static float max(final float... array) {// Validates inputvalidateArray(array);// Finds and returns maxfloat max = array[0];for (int j = 1; j < array.length; j++) {if (Float.isNaN(array[j])) {return Float.NaN;}if (array[j] > max) {max = array[j];}}return max;}/*** 校驗(yàn)參數(shù)數(shù)組是不是nulll或empty*/private static void validateArray(final Object array) {Validate.isTrue(array != null, "The Array must not be null");Validate.isTrue(Array.getLength(array) != 0, "Array cannot be empty.");}// 3 param min//-----------------------------------------------------------------------/*** 獲取三個(gè)long類型參數(shù)中最小的*/public static long min(long a, final long b, final long c) {if (b < a) {a = b;}if (c < a) {a = c;}return a;}/*** 獲取三個(gè)int類型參數(shù)中最小的*/public static int min(int a, final int b, final int c) {if (b < a) {a = b;}if (c < a) {a = c;}return a;}/*** 獲取三個(gè)short類型參數(shù)中最小的*/public static short min(short a, final short b, final short c) {if (b < a) {a = b;}if (c < a) {a = c;}return a;}/*** 獲取三個(gè)byte類型參數(shù)中最小的*/public static byte min(byte a, final byte b, final byte c) {if (b < a) {a = b;}if (c < a) {a = c;}return a;}/*** 獲取三個(gè)double類型參數(shù)中最小的*/public static double min(final double a, final double b, final double c) {return Math.min(Math.min(a, b), c);}/*** 獲取三個(gè)float類型參數(shù)中最小的* 如果有一個(gè)值是NaN，則NaN將返回，當(dāng)做無盡處理*/public static float min(final float a, final float b, final float c) {return Math.min(Math.min(a, b), c);}// 3 param max//-----------------------------------------------------------------------/*** 獲取三個(gè)long類型參數(shù)中最大的*/public static long max(long a, final long b, final long c) {if (b > a) {a = b;}if (c > a) {a = c;}return a;}/*** 獲取三個(gè)int類型參數(shù)中最大的*/public static int max(int a, final int b, final int c) {if (b > a) {a = b;}if (c > a) {a = c;}return a;}/*** 獲取三個(gè)short類型參數(shù)中最大的*/public static short max(short a, final short b, final short c) {if (b > a) {a = b;}if (c > a) {a = c;}return a;}/*** 獲取三個(gè)byte類型參數(shù)中最大的*/public static byte max(byte a, final byte b, final byte c) {if (b > a) {a = b;}if (c > a) {a = c;}return a;}/*** 獲取三個(gè)double類型參數(shù)中最大的*/public static double max(final double a, final double b, final double c) {return Math.max(Math.max(a, b), c);}/*** 獲取三個(gè)float類型參數(shù)中最大的*/public static float max(final float a, final float b, final float c) {return Math.max(Math.max(a, b), c);}//-----------------------------------------------------------------------/*** 判斷字符串僅僅包含數(shù)字字符* null或empty返回false*/public static boolean isDigits(final String str) {return StringUtils.isNumeric(str);}/*** 過時(shí)的方法被isCreatable取代*/@Deprecatedpublic static boolean isNumber(final String str) {return isCreatable(str);}/*** 校驗(yàn)String是否是一個(gè)有效的Java number* 校驗(yàn)number包含hexadecimal 的標(biāo)記 0x or 0X、八進(jìn)制數(shù)字、科學(xué)計(jì)數(shù)法和其他的數(shù)字標(biāo)記類型，比如1234L* 以0開頭的非十六進(jìn)制的數(shù)統(tǒng)一作為八進(jìn)制的數(shù)處理。所以String為09將返回false，因?yàn)?不是一個(gè)有效的八進(jìn)制。但是是以0.開頭的數(shù)字，都作為十進(jìn)制處理* null或empty或blank字符串返回false*/public static boolean isCreatable(final String str) {if (StringUtils.isEmpty(str)) {return false;}final 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 frontfinal int start = chars[0] == '-' || chars[0] == '+' ? 1 : 0;final boolean hasLeadingPlusSign = start == 1 && chars[0] == '+';if (sz > start + 1 && chars[start] == '0') { // leading 0if (chars[start + 1] == 'x' || chars[start + 1] == 'X') { // leading 0x/0Xint 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;} else if (Character.isDigit(chars[start + 1])) {// leading 0, but not hex, must be octalint i = start + 1;for (; i < chars.length; i++) {if (chars[i] < '0' || chars[i] > '7') {return false;}}return true;}}sz--; // don't want to loop to the last char, check it afterwords// for type qualifiersint 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 exponentreturn false;}hasDecPoint = true;} else if (chars[i] == 'e' || chars[i] == 'E') {// we've already taken care of hex.if (hasExp) {// two E'sreturn 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') {if (SystemUtils.IS_JAVA_1_6 && hasLeadingPlusSign && !hasDecPoint) {return false;}// no type qualifier, OKreturn true;}if (chars[i] == 'e' || chars[i] == 'E') {// can't have an E at the last bytereturn false;}if (chars[i] == '.') {if (hasDecPoint || hasExp) {// two decimal points or dec in exponentreturn false;}// single trailing decimal point after non-exponent is okreturn foundDigit;}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 or decimal pointreturn foundDigit && !hasExp && !hasDecPoint;}// last character is illegalreturn false;}// allowSigns is true iff the val ends in 'E'// found digit it to make sure weird stuff like '.' and '1E-' doesn't passreturn !allowSigns && foundDigit;}/*** 校驗(yàn)提供的字符串是否可以解析為number* 可解析的number包括下面方法可以執(zhí)行字符串 Integer.parseInt(String), Long.parseLong(String), Float.parseFloat(String) or Double.parseDouble(String). * 這個(gè)方法可以替代java.text.ParseException異常* 十六進(jìn)制和科學(xué)計(jì)數(shù)符號認(rèn)為是不可解析的* @since 3.4*/public static boolean isParsable(final String str) {if (StringUtils.isEmpty(str)) {return false;}if (str.charAt(str.length() - 1) == '.') {return false;}if (str.charAt(0) == '-') {if (str.length() == 1) {return false;}return withDecimalsParsing(str, 1);}return withDecimalsParsing(str, 0);}private static boolean withDecimalsParsing(final String str, final int beginIdx) {int decimalPoints = 0;for (int i = beginIdx; i < str.length(); i++) {final boolean isDecimalPoint = str.charAt(i) == '.';if (isDecimalPoint) {decimalPoints++;}if (decimalPoints > 1) {return false;}if (!isDecimalPoint && !Character.isDigit(str.charAt(i))) {return false;}}return true;}/****比例兩個(gè)int的大小，在Java7有提供相同的方法* @since 3.4*/public static int compare(final int x, final int y) {if (x == y) {return 0;}return x < y ? -1 : 1;}/*** 比例兩個(gè)long的大小，在Java7有提供相同的方法* @since 3.4*/public static int compare(final long x, final long y) {if (x == y) {return 0;}return x < y ? -1 : 1;}/*** 比例兩個(gè)long的大小，在Java7有提供相同的方法* @since 3.4*/public static int compare(final short x, final short y) {if (x == y) {return 0;}return x < y ? -1 : 1;}/*** 比例兩個(gè)byte的大小，在Java7有提供相同的方法*/public static int compare(final byte x, final byte y) {return x - y;} }

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常用方法

比較方法

NumberUtils.compare(x, y)

校驗(yàn)數(shù)字的

NumberUtils.isCreatable(str); NumberUtils.isDigits(str)

是否可以解析

NumberUtils.isParsable(str)

創(chuàng)建Java類型

NumberUtils.create*(str); NumberUtils.createBigDecimal(str);

將字符串轉(zhuǎn)換成數(shù)字類型，轉(zhuǎn)換失敗賦值默認(rèn)值

NumberUtils.toInt(str, defaultValue);

這個(gè)方法很厲害的，支持十六進(jìn)制，八進(jìn)制，科學(xué)計(jì)數(shù)法，和L,f的

NumberUtils.createNumber(str);

from:?https://blog.csdn.net/facekbook/article/details/77338293

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