Checking if an array has a certain character, why is my code not working?

Question

Hello here is some code to check for a valid character, although the code is not working. Even if 'operand' is a valid character it will never print yes, and return false. No matter what even if the character is valid it just doesn't recognize it and always goes to the else statement. Please help!

public static boolean checkValidOperands(char operand) {

    char[] validOperators = {'+', '-', '*', '/', 'q'};
    List<char[]> validOp = Arrays.asList(validOperators);
    if (validOp.contains(operand))  {
        System.out.println("Yes");
        return false;
    }  else {
        System.out.println("Please enter valid operand");
        return true;
    }
}

See this question: stackoverflow.com/questions/1248763/arrays-aslist-of-an-array Edit: Or @Reimeus answer — jonvuri
– jonvuri, Commented Mar 1, 2013 at 2:50
Are you sure the declaration for validOp shouldn't be a List<Char> rather than a List<Char[]>? You're not looking for a list of character arrays, but just characters... — David W
– David W, Commented Mar 1, 2013 at 2:51
Yup looks like this is the problem, I tried List<Char> but <Char> is not recognized... — Nearpoint
– Nearpoint, Commented Mar 1, 2013 at 2:54

Reimeus · Accepted Answer · 2013-03-01 02:50:50Z

7

You could use:

List<Character> validOp = Arrays.asList('+', '-', '*', '/', 'q');

answered Mar 1, 2013 at 2:50

Reimeus

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Comments

Community · Accepted Answer · 2017-05-23 11:50:43Z

The way you are creating a list of characters is wrong.

In your current code the list that you made is actually a list of character arrays, instead of characters.

import java.util.Arrays;
import java.util.List;

public class Test{
    public static void main(String[] args){
    char ch = '+';
    System.out.println(checkValidOperands(ch));

    }

    public static boolean checkValidOperands(char operand) {

        Character[] validOperators = {'+', '-', '*', '/', 'q'};
        List<Character> validOp = Arrays.asList(validOperators);
        if (validOp.contains(operand))  {
            System.out.println("Yes");
            return false;
        }  else {
            System.out.println("Please enter valid operand");
            return true;
        }
    }
}

PS: Also for future, do not use List<char>, List<int> etc.. as you cannot use a primitive type for generic in Java. Use their corresponding Object counter parts instead. Refer to this question for more information Why can Java Collections not directly store Primitives types?

John Henckel · Accepted Answer · 2015-03-30 17:00:43Z

0

A string is a better data structure for a set of characters. For example,

String validOperators = "+-*/q";

if (validOperators.indexOf(operand) != -1)  {
    System.out.println("Yes");
    return false;
}

answered Mar 30, 2015 at 17:00

John Henckel

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