How to determine whether a string is a number in java

public static boolean isNumericZidai(String str) { for (int i = 0; i < str.length(); i++) { System.out.println(str.charAt(i)); if (!Character.isDigit(str.charAt(i))) { return false; } } return true; }

public static void main(String[] args) { double aa = -19162431.1254; String a = "-19162431.1254"; String b = "-19162431a1254"; String c = "中文"; System.out.println(isNumericzidai(Double.toString(aa))); System.out.println(isNumericzidai(a)); System.out.println(isNumericzidai(b)); System.out.println(isNumericzidai(c)); }

false false false false

/** * 匹配是否为数字 * @param str 可能为中文，也可能是-19162431.1254，不使用BigDecimal的话，变成-1.91624311254E7 * @return * @date 2016年11月14日下午7:41:22 */ public static boolean isNumeric(String str) { // 该正则表达式可以匹配所有的数字 包括负数 Pattern pattern = Pattern.compile("-?[0-9]+(\\.[0-9]+)?"); String bigStr; try { bigStr = new BigDecimal(str).toString(); } catch (Exception e) { return false;//异常 说明包含非数字。 } Matcher isNum = pattern.matcher(bigStr); // matcher是全匹配 if (!isNum.matches()) { return false; } return true; }

public static boolean isNumeric(String str)Checks if the String contains only unicode digits. A decimal point is not a unicode digit and returns false. null will return false. An empty String ("") will return true. StringUtils.isNumeric(null) = false StringUtils.isNumeric("") = true StringUtils.isNumeric(" ") = false StringUtils.isNumeric("123") = true StringUtils.isNumeric("12 3") = false StringUtils.isNumeric("ab2c") = false StringUtils.isNumeric("12-3") = false StringUtils.isNumeric("12.3") = false Parameters: str - the String to check, may be null Returns: true if only contains digits, and is non-null