判断字符串为数字的三种方法

?java中判断字符串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;
}