JAVA 判斷輸入字串是否為字元或是奇偶數

// JAVA 判斷輸入字串是否為字元或是奇偶數
public class HelloWorld{

     public static void main(String []args)
     {
        //System.out.println("Hello World");
        String str= "123";
        String str1= "122";
        String str2= "1t2";
        String str3= "ttt";
        isNumeric(str);
        isNumeric(str1);
        isNumeric(str2);
        isNumeric(str3);
        
     }
     
     public  static  boolean  isNumeric(String str){   
  for  ( int  i  =  0 ; i  <  str.length(); i ++ ){   
   //System.out.println(str.charAt(i));   
   if  ( ! Character.isDigit( str.charAt(i)))
   {   
    System.out.println("輸入字串 "+ str + " is not int");
    return  false ;   
   }   
  }   
   //System.out.println("string is int");
   //這邊再把確定字串為數字再轉int做 x%2==0 就是偶數 反之則基數
  int i = Integer.parseInt(str);
   if (i %2 ==0)
   System.out.println("輸入字串 "+ str + " is 偶數");
   else
   System.out.println("輸入字串 "+ str + " is 奇數");
  return  true ;   
     
}  
}

//新版 

public class HelloWorld{

     public static void main(String []args)
     {
        //System.out.println("Hello World");
        String str= "1tttt1";
        boolean b = false;
       
        for  ( int  i  =  0 ; i  <  str.length(); i ++ )
            {   
                //System.out.println(str.charAt(i));   
                if  ( ! Character.isDigit( str.charAt(i)))
                {   
                    System.out.println("輸入字串 "+ str + " is not int"); 
                    b = true;
                    System.out.println(b);
                    break;
                     //System.out.println(i);    
                }  
            }   
            
            if(b ==false)
            {
                 int a = Integer.parseInt(str);
                 if (a %2 ==0)
                 {
                  System.out.println("輸入字串 "+ str + " is 偶數"); 
                   //getServletContext().setAttribute("str", "偶數");//
                   //response.sendRedirect("index.jsp");
                 //break; 
                 }
                 else 
                 {        
              System.out.println("輸入字串 "+ str + " is 奇數");
                  //getServletContext().setAttribute("str", "奇數");
                  //response.sendRedirect("index.jsp");
                  //break; 
                 } 
            }