Java .add(value) with lists

Question

Basically I've got an input string, my test string is '5 + 4' and I want to check character by character to create a list in the form [5,+,4], ie white spaces are ignored. Also, if my test string was '567+5-1' it would output [567,+,5,-,1] by concatenating the numbers together. Unfortunately, it won't let me do .add(inputChar) to my returnValue, saying symbol not found... any ideas?

import java.util.*;

public class CharacterArray {
    public List<String> splitToChar(String s) {
        List<String> returnValue = new LinkedList<String>();
        char[] chars = s.toCharArray();
        System.out.println(chars);
        int currentNumber;
        for (char inputChar : chars) {
            if (Character.isDigit(inputChar) == true) {
                currentNumber += inputChar;
            } else if (inputChar == '.') {
                currentNumber += inputChar;
            } else if (inputChar == '+') {
                returnValue.add(inputChar);
            } else if (inputChar == '-') {
                returnValue.add(inputChar);
            } else if (inputChar == '/') {
                returnValue.add(inputChar);
            } else if (inputChar == '*') {
                returnValue.add(inputChar);
            } else if (inputChar == '(') {
                returnValue.add(inputChar);
            } else if (inputChar == ')') {
                returnValue.add(inputChar);
            } else {
                System.out.println("Incorrect input symbol");
            }
        }
        return returnValue;
    }
}

If you're guaranteed whitespace, why not just split on whitespace? Also, you could use a switch. And check all the conditions at once, since they all do precisely the same thing. Also, pretty sure currentNumber += inputChar isn't what you want. — Dave Newton
– Dave Newton, Commented Jan 9, 2012 at 14:52
"I want to check character by character" What is the ultimate purpose of doing so? Is this an academic exercise, homework? If not, note that the ECMAScript (JavaScript) version of the ScriptEngine can evaluate string expressions. — Andrew Thompson
– Andrew Thompson, Commented Jan 9, 2012 at 14:57
I'm not guarenteed whitespace, I wan't it to accept either. Thanks — Coolmurr
– Coolmurr, Commented Jan 9, 2012 at 15:00

Gijs Overvliet · Accepted Answer · 2012-01-09 15:05:29Z

1

import java.util.*;

public class CharacterArray {
    public List<String> splitToChar(String s) {
        List<String> returnValue = new LinkedList<String>();
        char[] chars = s.toCharArray();
        System.out.println(chars);
        String currentNumber = "";
        for (char inputChar : chars) {
            if (Character.isDigit(inputChar) == true) {
                currentNumber += inputChar;
            } else if (inputChar == '.' ||
                    inputChar == '+' ||
                    inputChar == '-' ||
                    inputChar == '/' ||
                    inputChar == '*' ||
                    inputChar == '(' ||
                    inputChar == ')') {
                if (currentNumber.length() > 0){
                    returnValue.add(currentNumber);
                }
                currentNumber = "";
                returnValue.add(""+inputChar);
            }  else {
                System.out.println("Incorrect input symbol");
            }
        }
        if (currentNumber.length() > 0){
            returnValue.add(currentNumber);
        }
        return returnValue;
    }
}

By the way, your currentNumber should be a String

edited Jan 9, 2012 at 15:05

answered Jan 9, 2012 at 14:58

Gijs Overvliet

2,7013 gold badges30 silver badges35 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

Peter Lawrey Over a year ago

This will drop the last string if its a number.

Gijs Overvliet Over a year ago

Ah, yes, missed that.. After the for loop, check the length of currentNumber. If it's > 0, add it to the list..

Peter Lawrey Over a year ago

You should really check before each symbol as well. e.g. 5 * -3

David Soroko · Accepted Answer · 2012-01-09 14:52:31Z

1

how about .add(String.valueOf(inputChar)) ?

answered Jan 9, 2012 at 14:52

David Soroko

9,3843 gold badges44 silver badges59 bronze badges

Comments

Peter Lawrey · Accepted Answer · 2012-01-09 15:01:16Z

1

You can't add a char to a List<String> perhaps what you are trying to do is like

String currentNumber = "";
for (char inputChar : chars) {
    if (Character.isDigit(inputChar) || inputChar == '.') {
        currentNumber += inputChar;
    } else if ("+-/*()".indexOf(inputChar) >= 0) {
        if (currentNumber.length() > 0) returnValue.add(currentNumber);
        currentNumber = "";
        returnValue.add("" + inputChar);
    } else if (inputChar != ' ') {
        System.out.println("Incorrect input symbol '"+inputChar+"'");
    }
}
if (currentNumber.length() > 0) returnValue.add(currentNumber);

edited Jan 9, 2012 at 15:01

answered Jan 9, 2012 at 14:55

Peter Lawrey

535k83 gold badges770 silver badges1.2k bronze badges

3 Comments

Dave Newton Over a year ago

Same issue with currentNumber += inputChar.

Peter Lawrey Over a year ago

@DaveNewton, Fair point, I didn't want to be writing all his program for him. ;)

Dave Newton Over a year ago

I've always thought homework answers should employ a buginator, just not sure how to work it out.

murgatroid99 · Accepted Answer · 2012-01-09 15:02:18Z

0

Your returnValue is a List<String> but you are trying to add a char to the list. You can fix this by converting inputChar to a String when adding it to the list by using String.valueOf(inputChar).

edited Jan 9, 2012 at 15:02

answered Jan 9, 2012 at 14:53

murgatroid99

20.4k10 gold badges65 silver badges98 bronze badges

1 Comment

Roger Lindsjö Over a year ago

You can not cast a char to a String.

Collectives™ on Stack Overflow

Java .add(value) with lists

4 Answers 4

3 Comments

Comments

3 Comments

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

3 Comments

Comments

3 Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related