Java判断字符串是否是数字

• 使用正则表达式

  public class NumericCheck {
      private static final Pattern NUMBER_PATTERN = Pattern.compile("-?\\d+(\\.\\d+)?");
  
      public static boolean isNumeric(String str) {
          return str != null && NUMBER_PATTERN.matcher(str).matches();
      }
  
      public static void main(String[] args) {
          System.out.println(isNumeric("123")); // true
          System.out.println(isNumeric("-123.45")); // true
          System.out.println(isNumeric("abc")); // false
      }
  }

• 通过 Double.parseDouble 或 Integer.parseInt 转换字符串，捕获异常来判断

  public class NumericCheck {
      public static boolean isNumeric(String str) {
          try {
              Double.parseDouble(str);
              return true;
          } catch (NumberFormatException e) {
              return false;
          }
      }
  
      public static void main(String[] args) {
          System.out.println(isNumeric("123")); // true
          System.out.println(isNumeric("12.34")); // true
          System.out.println(isNumeric("abc")); // false
      }
  }

• 逐字符检查字符串是否仅包含数字字符（仅适用于整数）

  public class NumericCheck {
      public static boolean isNumeric(String str) {
          if (str == null || str.isEmpty()) return false;
          for (char c : str.toCharArray()) {
              if (!Character.isDigit(c)) return false;
          }
          return true;
      }
  
      public static void main(String[] args) {
          System.out.println(isNumeric("123")); // true
          System.out.println(isNumeric("12a3")); // false
      }
  }

• 使用 Apache Commons Lang

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

  import org.apache.commons.lang3.math.NumberUtils;
  
  public class NumericCheck {
      public static void main(String[] args) {
          System.out.println(NumberUtils.isCreatable("123")); // true
          System.out.println(NumberUtils.isCreatable("-12.34")); // true
          System.out.println(NumberUtils.isCreatable("0xFF")); // true
          System.out.println(NumberUtils.isCreatable("abc")); // false
      }
  }