检查字符串是否包含带for for循环的字符？

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!

Answer 1

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 if s in the for loop would work too as the conditions are mutually exclusive.

Answer 2

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 i th 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);
    }
}