在Java中使用Scanner提供多行输入

Question

My input will be

12
4.0
has to be concatenated with this input

My Expected output is

16
8.0
RandomString has to be concatenated with this input

My code which tries to do this is follows

        int i = 4;
        double d = 4.0;
        String s = "RandomString";

        Scanner scan = new Scanner(System.in);
        int j = scan.nextInt(); 
        double e = scan.nextDouble();
        String str = scan.nextLine();
        int resInt = i + j; double resDouble = d + e; String resString = s +" "+ str;
        System.out.println(resInt);
        System.out.println(resDouble);
        System.out.println(resString);

        scan.close();

This behaves differently. As soon as I enter two lines of input it is giving me output. Not waiting for third line of my input. So now my output is

12
4.0
16
8.0
RandomString

Answer 1

Primitive data types like int, double does not consume Enter key/End of line. That's why enter typed after keying integer is taken as value from buffer for your nextLine().

When you want to use the same scanner object with nextInt(), and a nextLine(), It doesn't work well.

There are two solutions to this, Solutions are to create another scanner to read string OR give an extra nextLine() before attempting to read the random string as given below.

Scanner scan = new Scanner(System.in);
int j = scan.nextInt();
double e = scan.nextDouble();
scan.nextLine();
String str = scan.nextLine();