通过正则表达式的方式来判断一个字符串是否为数字

//可以判断正负、整数小数
//StringUtils.isNum("a123") = false
//StringUtils.isNum("123a") = false
//StringUtils.isNum("1.23a") = false
//StringUtils.isNum("a1.23") = false
//StringUtils.isNum("123") = true
//StringUtils.isNum("12.3") = true
//StringUtils.isNum("0") = true
//StringUtils.isNum("-123") = true
//StringUtils.isNum("-12.3") = true

Boolean strResult = str.matches("^-?[0-9]+(.[0-9]+)?$");
if(strResult == true) {
    System.out.println("Is Number!");
} else {
    System.out.println("Is not Number!");
}