Java bestimmt, ob es sich um eine Dezimalzahl handelt

public class JudgeNumber {
     
   public static boolean judgeIsDecimal(String num){
         
        boolean isdecimal = false;
         
        if (num.contains(".")) {
             
             isdecimal=true;
              
        }
         
        return isdecimal;
         
    }
     
    public static void main(String[] args) {  //测试的main方法
         
        int num1 = 34;
         
        double num2=67.8;
         
        boolean is1 = judgeIsDecimal(String.valueOf(num1));
         
        boolean is2=judgeIsDecimal(String.valueOf(num2));
         
        System.out.println(is1);//fasle
         
        System.out.println(is2);//true
         
    }
     
}

public boolean contains(CharSequence s)