用Java一次输入不同的变量类型

Question

I made a calculator in C++ and i'm trying to recreate it mirror-like in Java.

There were 2 double variables( double a and double b )for the 2 operands and a char( char op ) to put in an if cycle, so for instace if op = '+' it will cout << a << op << b << "=" << a+b << endl; .

So i could write 12+2 in the console prompt and see 12+2=14 as output.

Now in Java i have to it one per line:

    Scanner Scin = new Scanner(System.in);
        System.out.println("OPERATION>");
        a = Scin.nextDouble();
        op = Scin.next().charAt(0);
        b = Scin.nextDouble();

And so i have to write a value and press return each time. How can i input all in one time like C++, and maybe do it in one line of code? Thanks in advance.

Answer 1

You can't read in multiple variables at once using Scanner , you will have to read them in one at a time. However, there is a nice way to allow the inputs to occur without hitting enter each time or inputting a space: set a different delimiter! The default delimiter is whitespace (which includes newlines), but you could also set it to the word boundary \\b from regex.

Scanner in = new Scanner(System.in).useDelimiter("\\b|\\s+");

Now you can read in 12+2 and it will split up the next calls where you want them, or you can continue to hit enter, or you can put spaces between the values. Your choice :D

To restore the delimiter to normal afterwards, use in.reset() .

Edit : To keep the word boundary from splitting the input at a decimal point, use the pattern:

(?<!\\.)\\b(?!\\.)|\\s+