How to implement Blacklist in java

Question

I would like to implement a method isInBlackList(String element), which return true, if element is founded in the blacklist. I have the following code:

public boolean isInBlackList(String element) {
        Set<String> blackList = new HashSet<String>();
        blackList.add("element1");
        blackList.add("element2");
        ...
        .....
        blackList.add("element20");

        return blackList.contains(element);
    }

What is bothering me is that I have to write add() method 20 times. Any better idea? it does not have to be implemented with Set.

Why are you adding, what appears to be, random elements to your blacklist when checking if an element is in the blacklist? — Zyn
– Zyn, Commented Apr 4, 2014 at 9:41
Well, is there better way to initial the blacklist with my 20 Elements? — Max_Salah
– Max_Salah, Commented Apr 4, 2014 at 9:42

Rahul Tripathi · Accepted Answer · 2014-04-04 09:44:35Z

3

You may try like this:

Set<String> blackList = new HashSet<String>(Arrays.asList("element1", "element2", "element3"));

answered Apr 4, 2014 at 9:44

Rahul Tripathi

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Comments

ccjmne · Accepted Answer · 2014-04-04 09:43:14Z

2

The simplest way I can think of is the following:

final List<String> blackList = Arrays.asList("element1", "element2", "element3");

As you can see, that's... really minimalist, and still works :)

answered Apr 4, 2014 at 9:43

ccjmne

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1 Comment

keyser Over a year ago

You missed the part about moving it outside of the method

Patrick · Accepted Answer · 2014-04-04 09:44:47Z

1

You can make blacklist a field of your class and initialize it with :

Set<String> blackList = new HashSet<String>(Arrays.asList("element1", ...));

answered Apr 4, 2014 at 9:44

Patrick

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Comments

newuser · Accepted Answer · 2014-04-04 09:46:17Z

1

Try this way,

Set<String> blackList = new HashSet<String>();

    public static void main(String[] args)
    {
        Test12 ss = new Test12();
        ss.populateBlackList();  // if the blacklist is fixed means you can call this in constructor 
        System.out.println(ss.isInBlackList("element1"));
    }

    private void populateBlackList() // make it as an seperate method dont populate at all time
    {
        for (int i = 1; i <= 20; i++)
        {
            blackList.add("element" + i);
        }
    }

    public boolean isInBlackList(String element) //finding the blackList
    {
        return blackList.contains(element);
    }

answered Apr 4, 2014 at 9:46

newuser

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1 Comment

Kresten Over a year ago

I think you misunderstood the question. By my understanding, the "element 1", "element 2" etc. was just an example

stinepike · Accepted Answer · 2014-04-04 09:43:12Z

0

declare blackList as a member variable and initialize it in constructor.
just use a for loop to add the elements

for( int i = 1; i<=20; i++){
```
string s = "element"+i;
    blackList.add(s);
}
```

answered Apr 4, 2014 at 9:43

stinepike

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