Question

Write a java statement to let the user enter an integer/double value from the keyboard

Answer 1

Answer:

The scheme used to represent integers is completely different from the scheme used to represent floating point. Even though you might regard 221 and 221.0 as equivalent, the bit patterns that they use are completely different.

Here is the 64-bit pattern that represents 221 using data type long (the spaces are not part of the pattern):

0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 1101 1101

Here is the 64-bit pattern that represents 221.0 using data type double:

0100 0000 0110 1011 1010 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000

And here is the 64-bit pattern for the four characters " 221"

0000 0000 0010 0000 0000 0011 0010 0000 0000 0011 0010 0000 0000 0011 0000 0001

Scanner does floating point input in a way similar to integer input. Use a Scanner object to scan through a stream of input characters and to convert them into a float or a double.

The methods that do this are nextFloat() and nextDouble().

Here is a program that inputs a string of characters and converts that string into primitive type double. The value is multiplied the by two, and then the original value and its double are converted back into characters and written to the screen.

import java.io.*;

import java.util.Scanner;

class DoubleDouble

{

public static void main (String[] args)

{

double value;

Scanner scan = new Scanner( System.in );

System.out.print("Enter a double:");

value = scan.nextDouble();

System.out.println("value: " + value +" twice value: " + 2.0*value );

}

}