If statement using == gives unexpected result [duplicate]

Answer 1

you might want to use equalsIgnoreCase(..) method for a finer refinement.

Answer 2

As the others said, you use object.equals(otherObject) to compare objects in Java.

But your approach is completely wrong.

Try instead

Set stopWords = new HashSet(Arrays.asList("s", "t", "am",
                                          "is", "are", "was", "were",
                                          "has", "have", "been",
                                          "will", "be", ...));

and then

private void refineWords() {
    words.removeAll(stopWords);
}

and you should be done.

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Further, note that with your current code you will get a ConcurrentModificationException because you try to change the collection while you're iterating over it.

So if you can't use the abovewords.removeAll(stopWords), then you must instead use the much more verbose Iterator.remove() method:

private void refineWords() {
    for (Iterator<String> wordsIterator = words.iterator(); wordsIterator.hasNext(); ) {
        String word = wordsIterator.next();
        if (stopWords.contains(word)) {
            wordsIterator.remove();
        }
    }
}

Answer 3

In java you need to compare strings with equals:

if(word.equals("s") ...

Answer 4

You need to use String.equals(), not ==. == checks if two Object references refer to the same Object:

if("s".equals(word) || "t".equals(word) || ...

From section 15.21.3 Reference Equality Operators == and != of the Java Language Specification 3.0:

While == may be used to compare references of type String, such an equality test determines whether or not the two operands refer to the same String object. The result is false if the operands are distinct String objects, even if they contain the same sequence of characters. The contents of two strings s and t can be tested for equality by the method invocation s.equals(t).