判断字符串中是否为数字的三种方法

//1用JAVA自带的函数
public static boolean isNumeric(String str){for (int i = str.length();--i>=0;){   if (!Character.isDigit(str.charAt(i))){return false;}}return true;}//2用正则表达式
public static boolean isNumeric(String str){ Pattern pattern = Pattern.compile("[0-9]*"); return pattern.matcher(str).matches();    } //3用ascii码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;
}