How can I get Doubles from a string after a specific key word?

Question

I tried many ways. this is the one I gave up on

    double prevClose = 0;

    String test = "this is a test test test stop 123 3.5";
    Scanner parse = new Scanner(test);
    while(parse.hasNext()) {
        if(parse.next("stop") == "stop")
            prevClose = parse.nextDouble();
    }

    return prevClose;

Answer 1

if(parse.next("stop") == "stop")

Above will never give you true. So prevClose will always be 0. Always do String comparisons with .equals() or equalsIgnoreCase() and not == opearator.

You can do the following

 while(parse.hasNext()) {
      if(parse.next().equalsIgnoreCase("stop"))
      prevClose = parse.nextDouble();
}

Answer 2

1. Compare Strings with equals.

2. Remove this next("stop") an call next() without parameters.

   double prevClose = 0;
   
   String test = "this is a test test test stop 123 3.5";
   Scanner parse = new Scanner(test);
   while(parse.hasNext()) {
       if(parse.next().equals("stop"))
           prevClose = parse.nextDouble();
   }
   
   System.out.println(prevClose);
   

   output: 123.0

Answer 3

Let's ignore the String == String problem in your code to start with and go a different direction...

Basically, all you want is all the text AFTER stop, for this we can use a combination of String#indexOf and String#substring

String test = "this is a test test test stop 123 3.5";
test = test.substring(test.indexOf("stop") + "stop".length()).trim();

Once you have the text you want, you can simply split the remaining text on the " " delimiter and you should have all the numbers in an array...

String parts[] = test.split(" ");
for (String part : parts) {
    System.out.println(part);
}

Which outputs...

123
3.5

For the String compare problem, you should take a look at How do I compare strings in Java? for more details

Answer 4

Try this

double prevClose = 0;

String test = "this is a test test test stop 123 3.5";
String[] split = test.split("stop");
String rightArray = split[1];
String[] numbers = rightArray.split(" ");
for (int i = 1; i < numbers.length; i++) {
    prevClose = Double.parseDouble(numbers[i]);
    System.out.println(prevClose);
}

Output :

123.0
3.5

Answer 5

Not only in String comparison but also another issues there.

    double prevClose = 0;
    String test = "this is a test test test stop 123 3.5";
    Scanner parse = new Scanner(test);
    while (parse.hasNext()) {
        if ("stop".equals(parse.next())) { // String comparison and next()
            prevClose = parse.nextDouble();
        }
    }
    System.out.println(prevClose);

Answer 6

Change to this

while(parse.hasNext()) {
    if(parse.next().equals("stop")) {
        prevClose = parse.nextDouble();
    }
}

Difference between == and equals - Since the String class override equals method, It return true if two String object contains same content but == will only return true if two references are pointing to same object.

Moreover Scanner#next()-Finds and returns the next complete token from this scanner.It does not accepts argument

Answer 7

    double prevClose = 0;

    String test = "this is a test test test stop 123 3.5";
   String[] test2 = test.split(" ");
   int i = 0;
    while(test2.length>i) {
        String string = test2[i];
        try {
            prevClose = Double.parseDouble(string);
            System.out.println(prevClose);
        } catch (NumberFormatException e) {
            //System.out.println("this is not number");
            //do nothing
        }

        i++;
    }

Ouptput :

123.0
3.5

This will work for any type of string independent of "stop"