CSIT115 Object Example: Scanners based on Strings (corrected, see yellow highlights)

Example from text, pg. 399, changed a little

Scanner input = new Scanner(“18.4 17.9 11 20”);  //Scanner constructor call

double x = input.nextDouble();   //scans “18.4 “ and puts 18.4 in x;

double y = input.nextDouble();   //scans “17.9 “ and puts 17.9 in y;

input.useRadix(16);  // changes scanner to a hex scanner

int x = input.nextInt();   // scans “11 “, puts 17 in x (one 16 plus one 1)

or the whole loop shown on pg. 399:

 Scanner input = new Scanner(“18.4 17.9 11 20”);

while (input.hasNextDouble()) {

double next = input.nextDouble();

System.out.println(next);

 }

which prints:

18.4

17.9

11.0

20.0

Note: also need import java.util.*; at top of program

We can imagine what’s in the Scanner object, its “object state”, or ”fields”

· The source String

· A value of the current position in the string

· The current radix

Just after construction: reference “input” pointing to Scanner object:

input

After first input.hasNextDouble() call in the loop: same as above, no change

After first input.nextDouble() call: internal position changes to 5, just at the space that delimited the first number:

ßactually position = 4, at the space after 18.4

After second input.nextDouble() call: internal position changes to 10, just at the space that delimited the second number:

ßactually position = 9, at the space after 17.9

After input.useRadix() call: internal radix changes to 16:

ßactually position = 9, at the space after 17.9

After input.nextInt() call: position steps past “11 “, nextInt returns int 17, the hex value of “11”.

ßactually position = 12, at the space after 11