simple String example

Question

i have the following piece of code but i could not detect why there is no output when i debug it , the control flow is never goes inside for loop but i cannot figure out why

could anyone please help me ? here is my code

public class DealWithStrings {
    ArrayList<String> container = new ArrayList<>();

    public void printDuplicate() {
        String string = "aaabed";
        String[] res = string.split("");

        for (int i = 1; i < string.length(); i++) {
            if (res[i] == res[i - 1]) {
                container.add(res[i]);
            }
        }

        for (String s : container) {
            System.out.println(s);
        }
    }

    public static void main(String[] args) {
        DealWithStrings d = new DealWithStrings();
        d.printDuplicate();
    }
}

it does go into the loop, the `if` never eveluates to `true` though — SomeJavaGuy, Dec 04 '17 at 12:36

score 3 · Answer 1 · edited Dec 04 '17 at 12:42

3

Compare String using .equals, not ==

Instead of

if(res[i]==res[i-1])

Use

if(res[i].equals(res[i-1]))

== will evaluate to true if the objects are the same, and in this case they never are. .equals will check if the contents of the Strings (the actual text) are the same.

edited Dec 04 '17 at 12:42

Henrik Aasted Sørensen

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answered Dec 04 '17 at 12:36

Stefan

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Why the downvote? – Stefan Dec 04 '17 at 12:39
Yes, why the downvote? Stack Overflow is so weird. – Stefan Reich Dec 04 '17 at 12:39
7

I´m not the one downvoting but it might be the case [that we shouldn´t answer on clear duplicates (answer well-asked questions)](https://stackoverflow.com/help/how-to-answer) – SomeJavaGuy Dec 04 '17 at 12:41
1

How helpful to punish someone with a negative number for that. – Stefan Reich Dec 04 '17 at 12:54

score 1 · Answer 2 · answered Dec 04 '17 at 12:55

Replace your code '==' operator with '.equals()' method, because , '==' equal operator compares the reference of the two characters in memory, whereas you need to check 'contents' at that reference.

And .equals method is overridden to check the content for Strings.

for (int i = 1; i < string.length(); i++) {
        if (res[i].equals(res[i - 1])) {
            container.add(res[i]);
        }
    }

simple String example

2 Answers2