Check if string contains a character with for loop?

Question

I am currently working on a simple code that will check if an user inputted String contains character(s) that are specified in the for loop.

My current code

import java.util.Scanner;
public class AutumnLeaves {
public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int G = 0;
    int R = 0;
    int Y = 0;
    int B = 0;
    String S = sc.nextLine();
    for (int i = 0; i < S.length(); i++) {
        if (S.contains("G")) {
            G++;
        } else {
            if (S.contains("R")) {
                R++;
            } else {
                if (S.contains("Y")) {
                    Y++;
                } else {
                    if (S.contains("B")) {
                        B++;
                    }
                }
            }
        }
    }
    int total = G + R + Y + B;
    System.out.println(G/total);
    System.out.println(R/total);
    System.out.println(Y/total);
    System.out.println(B/total);
}

}

As you can see, it checks if the string contains such characters and it will increase the counter of the character by one. However when I run it, I don't receive the results I predicted. If I input GGRY, it outputs 1 0 0 0. When the desired out put is

0.5 0.25 0.25 0.0

Any help would be appreciated!

The total works but I'm having trouble with the division part. — Glace
– Glace, Commented Apr 2, 2017 at 22:03

Marcy · Accepted Answer · 2017-04-02 22:09:23Z

6

The problem is that S.contains returns true if the whole string contains the given character. S.charAt should solve your problem:

for (int i = 0; i < S.length(); i++) {
    if (S.charAt(i) == 'G') G++;
    else if (S.charAt(i) == 'R') R++;
    else if (S.charAt(i) == 'Y') Y++;
    else if (S.charAt(i) == 'B') B++;
}

Also, dividing integers will return an integer (rounded down). As such your output would always be 0 unless all the characters are the same. Just cast them to double before printing:

System.out.println((double) G/total);
System.out.println((double) R/total);
System.out.println((double) Y/total);
System.out.println((double) B/total);

Edit: As pointed out by Sumit Gulati in a comment, a switch statement will have better performance in Java 7. Also, as David Conrad pointed out using only ifs in the for loop would work too as the conditions are mutually exclusive.

edited Apr 2, 2017 at 22:09

answered Apr 2, 2017 at 21:42

Marcy

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3 Comments

David Conrad Over a year ago

(The else's aren't strictly needed, since the conditions are mutually exclusive.)

Sumit Gulati Over a year ago

If you are using Java 7, use switch case. It has better performance.

Glace Over a year ago

I am currently using IntelliJ Idea with Java8, but will definitely use switch case if I some how change to 7, thanks.

Devendra Lattu · Accepted Answer · 2017-04-02 21:48:07Z

Your earlier code S.contains("some character") was finding the index of the character in the entire string. Use S.charAt(i) to specifically find the index at ith location in the string. Finally, you need to convert the integer to floating point in order to print output as floating values.

public class AutumnLeaves {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int G = 0;
        int R = 0;
        int Y = 0;
        int B = 0;
        String S = sc.nextLine();
        for (int i = 0; i < S.length(); i++) {
            if (S.charAt(i) == 'G') {
                G++;
            } else {
                if (S.charAt(i) == 'R') {
                    R++;
                } else {
                    if (S.charAt(i) == 'Y') {
                        Y++;
                    } else {
                        if (S.charAt(i) == 'B') {
                            B++;
                        }
                    }
                }
            }
        }
        int total = G + R + Y + B;
        System.out.println(G * 1.0 / total);
        System.out.println(R * 1.0 / total);
        System.out.println(Y * 1.0 / total);
        System.out.println(B * 1.0 / total);
    }
}

Why does multiplying the variable by 1.0 work? When I multiply it by 1 I get a totally different result.
Multiplying by 1.0 which is of type double automatically converts the expression to type double. So 5/2 = 2 if not double. However, 5.0/2 = 2.5 since it is now a double :)
Ah that's cool! So when I multiply it by 1 the compiler is actually rounding it to the nearest whole number because it's an integer. I reckon adding (double) would work too as stated by Leon.
I have upvoted the answer but I need 15 reputation for it to be visible! Sorry about that

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