JAVA判断字符串是否为数字

String转Character数组，用Character的isDigit和isLetter函数去判断。
public static boolean isNumeric(String str) {
for (int i = str.length(); i = 0;) {
if (!Character.isDigit(str.charAt(i))) {
return false;
}
}
return true;
}
public static boolean isNumeric(String str) {
Pattern pattern = Pattern.compile("[0-9]*");
return pattern.matcher(str).matches();
}
public static boolean isNumeric(String str) {
if (str.matches("““d*")) {
return true;
}
return false;
}
public static boolean isNumeric(String str) {
for (int i = str.length(); i = 0;) {
int chr = str.charAt(i);
if (chr 48chr 57)
return false;
}
return true;
}