StringUtils.isNumeric判断是否是数字字符串
org.apache.commons.lang3.StringUtils
字符串工具类StringUtils能够很方便的处理Java字符串问题，简直是Java字符串的一大法宝
可以记录下常用的功能，即便对于字符串对象为null，也是轻松处理
IsEmpty/IsBlank - checks if a String contains text Trim/Strip - removes leading and trailing whitespace Equals/Compare - compares two strings null-safe startsWith - check if a String starts with a prefix null-safe endsWith - check if a String ends with a suffix null-safe IndexOf/LastIndexOf/Contains - null-safe index-of checks IndexOfAny/LastIndexOfAny/IndexOfAnyBut/LastIndexOfAnyBut - index-of any of a set of Strings ContainsOnly/ContainsNone/ContainsAny - does String contains only/none/any of these characters Substring/Left/Right/Mid - null-safe substring extractions SubstringBefore/SubstringAfter/SubstringBetween - substring extraction relative to other strings Split/Join - splits a String into an array of substrings and vice versa Remove/Delete - removes part of a String Replace/Overlay - Searches a String and replaces one String with another Chomp/Chop - removes the last part of a String UpperCase/LowerCase/SwapCase/Capitalize/Uncapitalize - changes the case of a String CountMatches - counts the number of occurrences of one String in another IsAlpha/IsNumeric/IsWhitespace/IsAsciiPrintable - checks the characters in a String DefaultString - protects against a null input String Reverse/ReverseDelimited - reverses a String StringUtils.isNumeric
其中需要注意的是 StringUtils.isNumeric 在判断是否是数字字符串的时候，无法包含所有情况
官网上也有实例说明，对于含有特殊符号的字符串，是无法解析的
完整的判断
如果要完整判断一个字符串是不是数字字符串，最方便的就是借助math中的BigDecimal类，如果不是数字就会跑出异常，这时候捕获就可以判定为非数字
如果确定输入数据不包含正负号、小数点的话，可以直接使用，会提高很多性能，否则需要借助BigDecimal类来完整判别
import java.math.BigDecimal; public static boolean isNumeric(String str) { try { new BigDecimal(str); } catch (Exception e) { return false; } return true; } 构造函数源码
// BigDecimal类的相应的构造函数源码，可以看到，它考虑到了很多情况，非常经典，值得好好学习 public BigDecimal(char[] in, int offset, int len, MathContext mc) { // protect against huge length. if (offset + len > in.length || offset < 0) throw new NumberFormatException("Bad offset or len arguments for char[] input."); // This is the primary string to BigDecimal constructor; all // incoming strings end up here; it uses explicit (inline) // parsing for speed and generates at most one intermediate // (temporary) object (a char[] array) for non-compact case. // Use locals for all fields values until completion int prec = 0; // record precision value int scl = 0; // record scale value long rs = 0; // the compact value in long BigInteger rb = null; // the inflated value in BigInteger // use array bounds checking to handle too-long, len == 0, // bad offset, etc. try { // handle the sign boolean isneg = false; // assume positive if (in[offset] == '-') { isneg = true; // leading minus means negative offset++; len--; } else if (in[offset] == '+') { // leading + allowed offset++; len--; } // should now be at numeric part of the significand boolean dot = false; // true when there is a '.' long exp = 0; // exponent char c; // current character boolean isCompact = (len <= MAX_COMPACT_DIGITS); // integer significand array & idx is the index to it. The array // is ONLY used when we can't use a compact representation. int idx = 0; if (isCompact) { // First compact case, we need not to preserve the character // and we can just compute the value in place. for (; len > 0; offset++, len--) { c = in[offset]; if ((c == '0')) { // have zero if (prec == 0) prec = 1; else if (rs != 0) { rs *= 10; ++prec; } // else digit is a redundant leading zero if (dot) ++scl; } else if ((c >= '1' && c <= '9')) { // have digit int digit = c - '0'; if (prec != 1 || rs != 0) ++prec; // prec unchanged if preceded by 0s rs = rs * 10 + digit; if (dot) ++scl; } else if (c == '.') { // have dot // have dot if (dot) // two dots throw new NumberFormatException(); dot = true; } else if (Character.isDigit(c)) { // slow path int digit = Character.digit(c, 10); if (digit == 0) { if (prec == 0) prec = 1; else if (rs != 0) { rs *= 10; ++prec; } // else digit is a redundant leading zero } else { if (prec != 1 || rs != 0) ++prec; // prec unchanged if preceded by 0s rs = rs * 10 + digit; } if (dot) ++scl; } else if ((c == 'e') || (c == 'E')) { exp = parseExp(in, offset, len); // Next test is required for backwards compatibility if ((int) exp != exp) // overflow throw new NumberFormatException(); break; // [saves a test] } else { throw new NumberFormatException(); } } if (prec == 0) // no digits found throw new NumberFormatException(); // Adjust scale if exp is not zero. if (exp != 0) { // had significant exponent scl = adjustScale(scl, exp); } rs = isneg ? -rs : rs; int mcp = mc.precision; int drop = prec - mcp; // prec has range [1, MAX_INT], mcp has range [0, MAX_INT]; // therefore, this subtract cannot overflow if (mcp > 0 && drop > 0) { // do rounding while (drop > 0) { scl = checkScaleNonZero((long) scl - drop); rs = divideAndRound(rs, LONG_TEN_POWERS_TABLE[drop], mc.roundingMode.oldMode); prec = longDigitLength(rs); drop = prec - mcp; } } } else { char coeff[] = new char[len]; for (; len > 0; offset++, len--) { c = in[offset]; // have digit if ((c >= '0' && c <= '9') || Character.isDigit(c)) { // First compact case, we need not to preserve the character // and we can just compute the value in place. if (c == '0' || Character.digit(c, 10) == 0) { if (prec == 0) { coeff[idx] = c; prec = 1; } else if (idx != 0) { coeff[idx++] = c; ++prec; } // else c must be a redundant leading zero } else { if (prec != 1 || idx != 0) ++prec; // prec unchanged if preceded by 0s coeff[idx++] = c; } if (dot) ++scl; continue; } // have dot if (c == '.') { // have dot if (dot) // two dots throw new NumberFormatException(); dot = true; continue; } // exponent expected if ((c != 'e') && (c != 'E')) throw new NumberFormatException(); exp = parseExp(in, offset, len); // Next test is required for backwards compatibility if ((int) exp != exp) // overflow throw new NumberFormatException(); break; // [saves a test] } // here when no characters left if (prec == 0) // no digits found throw new NumberFormatException(); // Adjust scale if exp is not zero. if (exp != 0) { // had significant exponent scl = adjustScale(scl, exp); } // Remove leading zeros from precision (digits count) rb = new BigInteger(coeff, isneg ? -1 : 1, prec); rs = compactValFor(rb); int mcp = mc.precision; if (mcp > 0 && (prec > mcp)) { if (rs == INFLATED) { int drop = prec - mcp; while (drop > 0) { scl = checkScaleNonZero((long) scl - drop); rb = divideAndRoundByTenPow(rb, drop, mc.roundingMode.oldMode); rs = compactValFor(rb); if (rs != INFLATED) { prec = longDigitLength(rs); break; } prec = bigDigitLength(rb); drop = prec - mcp; } } if (rs != INFLATED) { int drop = prec - mcp; while (drop > 0) { scl = checkScaleNonZero((long) scl - drop); rs = divideAndRound(rs, LONG_TEN_POWERS_TABLE[drop], mc.roundingMode.oldMode); prec = longDigitLength(rs); drop = prec - mcp; } rb = null; } } } } catch (ArrayIndexOutOfBoundsException e) { throw new NumberFormatException(); } catch (NegativeArraySizeException e) { throw new NumberFormatException(); } this.scale = scl; this.precision = prec; this.intCompact = rs; this.intVal = rb; } 参考
文章来源: https://blog.csdn.net/whgyxy/article/details/97015820