CODEWITHSUNDEEP
javaconditional-statements
Maljam
Maljam

Reputation: 6274

Is there a way to dynamically change conditions in if statement in Java?

I have this code that filters a String str, keeping only some chars, resulting in the reduced String fStr. The subtlety is that I only keep a target char, if it is not equal to the last char in fStr: 

ArrayList<Character> targetChars = //{a, b, c};
String str = "axxbxxxxbxbxcxa", fStr = "";

for(int i = 0, s = 0 ; i < str.length() ; i++) {
    char c = str.charAt(i);
    if(targetChars.contains(c)) {
        if(s > 0 && fStr.charAt(s-1) != c) {
            fStr += c;
            s++;
        }
    }
}

fStr → "abca"

In the innermost if statement, I have to include s > 0 before fStr.charAt(s-1) != c, otherwise the latter will throw an OutOfBounds exception the first time targetChars.contains(c) is true. But only the first time, it annoys me that the loop will always check that I won't be out of bounds, given that it only has to do it once. I know I could do something like that: 

ArrayList<Character> targetChars = //{a, b, c};
String str = "auebskrubnbocpa", fStr = "";
int i = 0, s = 0;   

for(; i < str.length() ; i++) {
    char c = str.charAt(i);
    if(targetChars.contains(c)) {
            fStr += c;
            s++;
            i++;
            break;
    }
}

for(; i < str.length() ; i++) {
    char c = str.charAt(i);
    if(targetChars.contains(c)) {
        if(fStr.charAt(s-1) != c) {
            fStr += c;
            s++;
        }
    }
}

But is there a more elegant and less annoying way to dynamically truncate a conditional statement?

Upvotes: 0

Views: 2623

Answers (3)

Constantin
Constantin

Reputation: 1506

Here is how I would do it, but not sure if it suits your needs

public class Example {

public static void main(String[] args) {
    char[] targetChars = {'a', 'b', 'c'};
    String str = "axxbxxxxbxbxcxa", fStr = " ";

    for(int i = 0 ; i < str.length() ; i++) {
        char c = str.charAt(i);
        if(isAcceptableChar(c, targetChars)) {

            if(fStr.charAt(fStr.length() - 1) != c) {
                fStr = fStr.trim() + c;
            }
        }
    }

    System.out.println(fStr);       
}


private static boolean isAcceptableChar(char newChar, char[] targetChars) {
    boolean value = false;

    for(char ch : targetChars){
        if(ch == newChar) {
            value = true;
            break;
        }
    }
    return value;
}   
}

Upvotes: 1

dgsomerton
dgsomerton

Reputation: 115

Sure there is, just call a function that returns a boolean value that you use in your if condition. Different functions could be called at different times by using a function pointer.

Upvotes: 0

Stephen C
Stephen C

Reputation: 718946

Is there a way to dynamically change conditions in if statement in Java?

No there isn't. The original version of your code is the best from a readability perspective.

However, if you are concerned about efficiency, then you should be using a StringBuilder rather than fStr += c.

Also a char[] and an explicit for loop is likely to be faster than ArrayList<Character>.contains.

Upvotes: 2

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