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;

}