使用if语句检查While循环

Question

The while loop and if statement work through the first iteration. After it completes and it prints "Do you want another time?" and I input "Y" the program terminates and I don't know why. My logic and syntax seem to be correct but there is always flaws that I cant see with my own eyes. I would appreciate it if someone can point the flaw out.

while (!check) {
    str = in.nextLine();
    if (in.hasNextLine() && str.equals("Y")) {
        hours = ran.nextInt(11) + 1;
        minutes = ran.nextInt(60);
        if (minutes < 10) {
            System.out.println(hours + ":" + "0" + minutes);
        } else {
            System.out.println(hours + ":" + minutes);
        }
        System.out.println("Do you want another time?");

    } else {
        check = true;
    }
}

Answer 1

You shouldn't be checking to see if you have another line in the buffer; you can just explicitly check the input you get back through str instead. The likely reason you're exiting out of the loop the first time is due to in.hasNextLine() being false.

So, this means that you'd change your if statement to:

if(str.equals("Y")) {

}

Answer 2

You are trying to see if there is a next line ( in.hasNextLine() ), after you have already read it.

Try this way:

       while (!check) {
            if(in.hasNextLine()){
                System.out.println("Do you want another time?");
                str = in.nextLine();
                if("Y".equals(str)){
                    hours = ran.nextInt(11) + 1;
                    minutes = ran.nextInt(60);
                    if (minutes < 10) {
                        System.out.println(hours + ":" + "0" + minutes);
                    } else {
                        System.out.println(hours + ":" + minutes);
                    }
                    System.out.println("Do you want another time?");
                }
            }else{
                check = true;
            }
        }

Ok, here's a nicer way to do this whole thing:

while (in.hasNextLine()) {
        System.out.println("Do you want another time?");
        if("Y".equals(in.nextLine())){
            //do what you want to do
        }else{
          //perhaps you want to break, or whatever you want to do
          break;
        }
    }

Answer 3

Here Is what you looking for.

while (!check) {        

        hours = ran.nextInt(11) + 1;
        minutes = ran.nextInt(60);

        if (minutes < 10) {
            System.out.println(hours + ":" + "0" + minutes);
        } 
        else {
            System.out.println(hours + ":" + minutes);
        }

        System.out.println("Do you want another time?");
        str = in.nextLine();

        if(str.equals("Y"))
          check = false;
        else
        check = true;   

}

What I changed is, I am comparing the str after taking the input. if its "Y" it will continue otherwise it will go out of the while loop.