CODEWITHSUNDEEP
javaif-statementdesign-patterns
Anna
Anna

Reputation: 39

Design pattern for many if statement and Boolean condition?

I am wondering if there is any design pattern for such situation:

private static boolean check(String s) {
    if(isBook(s)) {
        System.out.println("Book");
        return false;
    }else if(isEmail(s)) {
        System.out.println("Email");
        return false;
    }
    return true;
}

private static boolean isBook(String s) {
    if(s.equals("B")) return true;
    return false;
}

private static boolean isEmail(String s) {
    if(s.equals("E")) return true;
    if(s.length() > 4) return true;
    return false;
}

There will be many isXXX in check method, but I don't wanna to have many if-else statement.

Upvotes: 0

Views: 1224

Answers (2)

Spotted
Spotted

Reputation: 4091

Since you have many isXXX checks, I would make the system more generic in order to avoid a huge switch (or if/else)

private static boolean check(String s, Collection<Predicate<String>> rules)
{
    return rules.stream()
                .noneMatch(rule -> rule.test(s));
}

Declare your rules as follow

Predicate<String> isBook = s -> s.equals("B");
Predicate<String> isEmail = s -> s.equals("E") || s.length() > 4;

Usage

check("E", Arrays.asList(isBook, isEmail)); //false
check("B", Arrays.asList(isBook, isEmail)); //false
check("Emo", Arrays.asList(isBook, isEmail)); //true
check("Email", Arrays.asList(isBook, isEmail)); //false

Upvotes: 1

Glenner003
Glenner003

Reputation: 1637

Instead of creating an is... method for each possible type, introduce an enumeration and make one method that returns the type.

This way you can easily use a switch statement.

Upvotes: 1

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