Java: Check if a string is in a dictionary

Question

I have a language dictionary (i.e. english,italian,etc...), that essentially is a file with one word on every line.

Now i want to create a class with a method that given a string in input check if that string exists into that dictionary.

My idea is that the method return a boolean value. In pseudocode:

boolean checkWord(String s){
    if(StringIsInDictionary) return true;
    return false
}

What should be the best way to implement that feature?

Consider that the file will contain ~65000 words.

Oli actually i haven't tried nothing.

Ivan
– Ivan

2013-03-02 15:40:59 +00:00
Commented Mar 2, 2013 at 15:40 — Ivan
– Ivan, Commented Mar 2, 2013 at 15:40

NPE · Accepted Answer · 2013-03-02 15:33:23Z

7

Read the dictionary into a Set<String> (for example, HashSet<String>), and then use set.contains(word).

answered Mar 2, 2013 at 15:33

NPE

503k114 gold badges970 silver badges1k bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Matt Ball Over a year ago

And consider using a HashSet constructor which takes an initialCapacity parameter. docs.oracle.com/javase/7/docs/api/java/util/…

Ivan Over a year ago

Is it efficient also for smartphones?

lreeder · Accepted Answer · 2013-03-02 16:05:34Z

2

For a space and time efficent solution (like you might use on a smartphone), consider a bloom filter. Then you won't need to store the dictionary on the phone, and checking that a string is in a dictionary will be very fast. Note that a bloom filter may return a false positive, but you can tune it to reduce that risk.

There are several open-source Java implementations of bloom filters out there. One is here https://github.com/magnuss/java-bloomfilter.

answered Mar 2, 2013 at 16:05

lreeder

12.3k2 gold badges60 silver badges68 bronze badges

1 Comment

Joni Over a year ago

+1, A Bloom filter is optimal for situations where memory and performance are constrained.

Polygnome · Accepted Answer · 2013-03-02 15:35:34Z

1

You will probably not want to store the words as one word per line. A better approach might be to read the file from disk only once, store the words in a HashSet (a set backed by a HashMap, which is very efficient to search), and then use set.contains("mystring"). This will, however, require the whole map to be in memory, but it will be very efficient when you need to check multiple words.

You could then even go back and serialize the set in a more efficient manner to disk, making the initial loading faster.

answered Mar 2, 2013 at 15:35

Polygnome

7,8092 gold badges41 silver badges60 bronze badges

Comments

Community · Accepted Answer · 2017-05-23 12:33:32Z

1

Take a look at this question, I think it could help you. Fastest way to find a string in a text file with java

edited May 23, 2017 at 12:33

CommunityBot

11 silver badge

answered Mar 2, 2013 at 15:43

maxivis

1,8074 gold badges24 silver badges39 bronze badges

Collectives™ on Stack Overflow

Java: Check if a string is in a dictionary

4 Answers 4

2 Comments

1 Comment

Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

2 Comments

1 Comment

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related