int i = 0;
??while(i<3){
???System.out.println("請輸入ID");
???Integer input = Input.nextInt();
???Course m1 = mapList.get(Input);
???//System.out.println(m1);????????????? //這里m1為null
???if(m1==null){
????System.out.println("請輸入姓名");
????String n1 = Input.next();
????mapList.put(input,new Course(input,n1));
????//System.out.println(m1);???????? //這里m1依舊為null
??i++;
???}
???else{
????System.out.println("ID被占用");
????continue;
???}

直到循環結束后m1才有值? 導致else沒法執行。。怎么破