Java程序中的对角线和直线图

Question

in the program below you can see that i've allowed the input of the user to give a direction such as n100 which will draw a line north and move it 100 spaces but How am I able to allow the sketch program to do diagonal lines as well as straight lines , I understand I am able to change the input to (0,2) to allow diagonal lines by using something like ne but then my program doesn't like when I use directions such as n, e, s, w. What can I do to allow both lines? this is the code below:

boolean okToProcess = true;
    String message = "";
    int colourInt;

    String input = in.getText();
    String direction = input.substring(0, 1);
    String distance = input.substring(1);

    double distanceAsDouble = 0;



    if (direction.equals("n"))
        t.heading(0);
    else if (direction.equals("ne"))
        t.heading(45);
    else if (direction.equals("e"))
        t.heading(90);
    else if (direction.equals("se"))
        t.heading(135);
    else if (direction.equals("s"))
        t.heading(180);
    else if (direction.equals("sw"))
        t.heading(225);
    else if (direction.equals("w"))
        t.heading(270);
    else if (direction.equals("nw"))
        t.heading(315);
    else {
        okToProcess = false;
        message += "bad direction: " + direction + " ";
    }


    if (isNumeric(distance)) {
        distanceAsDouble = Double.parseDouble(distance);
    }
    else{
        okToProcess = false;
        message += "bad distance: " + distance;
    }

    if (okToProcess) {
        if (!EtchASketchClipped(t, distanceAsDouble)) {
            t.setLineWidth(3);

Answer 1

If you use

String direction = input.substring(0, 1);
String distance = input.substring(1);

you are storing and comparing only the first character of the string and eventually assign an invalid number to distance, as if the direction is diagonally, the second character is prepended to direction. Use String.startsWith() to check for a given direction. Inside the if-statement, decide wether to start the distance at the second or third character. You can also just use input as a value to check.

...
String distance ;
double distanceAsDouble = 0;

if (input.startsWith("n")) {
    t.heading(0);
    distance = input.substring(1);
} else if (input.startsWith("ne")) {
    t.heading(45);
     distance = input.substring(2);
} else if ...

Answer 2

String direction = input.replaceFirst("^(\\D*)(.*)$", "$1");
String distance = input.replaceFirst("^(\\D*)(.*)$", "$2").trim();

Where the regular expression means

• \\\\D matches non-digit
• \\\\d matches digit
• postfix * for 0 or more
• . for any char
• ^ begin
• $ end
• () group numbered from 1
• $1 group 1