Comparing two String arrays

Question

I'm making a program that compares two text files and returns their similarity (based on a given algorithm). For each unique word in the first file, I want to find the probabilities that they occur in the second file. But whenever I run my program the similarity returned is always 0.0. This is what I have right now:

public static double nestedLoop(String[] doc1, String[] doc2) {
    // nested loop: sort doc1, for each unique word in doc1, find all
    // occurences in doc2 using a sequential search

    java.util.Arrays.sort(doc1);

    double similarity = 0.0;

    for (int i = 0; i < doc1.length - 1; i++) {
        if (doc1[i] != doc1[i + 1]) {
        String unique = doc1[i];
        double count = 0.0;
            for (int j = 0; j < doc2.length; j++) {
                if (unique == doc2[j]) {
                    count++;
                    similarity += count / doc2.length;
                }
            }
        }
    }
    return similarity;
}

Can someone tell me what is going on?

Community · Accepted Answer · 2017-05-23 11:43:09Z

9

if (unique == doc2[j]) {

should be

if (unique.equals(doc2[j])) {

Same for if (doc1[i] != doc1[i + 1]) {

should be:

 if (!(doc1[i].equals(doc1[i + 1]))) {

String comparison should always use equals() instead of == (except case of String literal comparison)

Please read How do I compare strings in Java?

edited May 23, 2017 at 11:43

CommunityBot

11 silver badge

answered Nov 8, 2012 at 18:39

kosa

66.7k15 gold badges135 silver badges170 bronze badges

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

4 Comments

yiwei Over a year ago

WOOOOOW I am stupid. I've definitely run into this before. I'll give it a try. Thanks!

yiwei Over a year ago

actually, one more small question. If I have to use equals() for String comparison, how come in the first if statement I can use the != to compare doc1[i] and doc[i + 1]? Aren't they also Strings?

kosa Over a year ago

@59eagle: Valid question, yes you need to use .equals() there also.

kosa Over a year ago

@ColinD: Added clarification.

Collectives™ on Stack Overflow

Comparing two String arrays

1 Answer 1

4 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

4 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related