Java method to determine whether a string is an integer

java判断字符串是否为整数的方法：

方法一：用JAVA自带的函数

/**
 *
 * @Description: 用JAVA自带的函数
 *
 * @param str
 * @return
 * @return: boolean
 * @Version: 0.0.1
 */
public static boolean isOne(String str) {
  for (int i = str.length(); --i >= 0;) {
     if (!Character.isDigit(str.charAt(i))) {
        return false;
       }
    }
 return true;
 }

方法二：

/**
 *
 * @Description: 判断是否为整数
 *
 * @param str
 * @return
 * @return: boolean
 * @Version: 0.0.1
 */
    public static boolean isTwo(String str) {
        Pattern pattern = Pattern.compile("^[-\\+]?[\\d]*$");
        return pattern.matcher(str).matches();
    }

方法三：

    /**
     * @Description:
     * @param str
     * @return
     * @return: boolean
     * @Version: 0.0.1
     */
    public static boolean isNumeric(String str) {
        Pattern pattern = Pattern.compile("[0-9]*");
        return pattern.matcher(str).matches();
    }

方法四：

    /**
     * @Description:
     * @param s
     * @return
     * @return: boolean
     * @Version: 0.0.1
     */
    public final static boolean isNumeric(String s) {
        if (s != null && !"".equals(s.trim()))
            return s.matches("^[0-9]*$");
        else
            return false;
    }

方法五：用ascii码

  /**
     * @Description:
     * @param str
     * @return
     * @return: boolean
     * @Version: 0.0.1
     */
    public static boolean isNumeric(String str) {
        for (int i = str.length(); --i >= 0;) {
            int chr = str.charAt(i);
            if (chr < 48 || chr > 57)
                return false;
        }
        return true;
    }

方法六：

/**
     * @Description: 判断double是否是整数
     * @param obj
     * @return
     * @return: boolean
     * @Version: 0.0.1
     */
    public static boolean isIntegerForDouble(double obj) {      
        double eps = 1e-10;  
        // 精度范围      
        return obj-Math.floor(obj) < eps;  
    }

更多java知识请关注java基础教程栏目。

The above is the detailed content of Java method to determine whether a string is an integer. For more information, please follow other related articles on the PHP Chinese website!