Java string comparison not working as intended

Question

I've done quite a bit of string comparisons in java in the past, but this time it doesn't seem to work.
I'm aware of the fact, that you have to use the .equals() function in order to compare strings in java.

In my attempt to figure out what's wrong, I wrote the following code snippet:
Log.e("testLogic", String.valueOf(taken.getText().toString().trim().equals('1'))); Log.e("testValue", taken.getText().toString().trim());
producing the following result:

E/testLogic﹕ false
E/testValue﹕ 1
E/testLogic﹕ false
E/testValue﹕ 1
E/testLogic﹕ false
E/testValue﹕ 0

This seems rather strange, since the two first 'testLogic' logs should produce true.
The code is used in a custom list adapter if it means anything.

/Mikkel

'1' is a char, not a String. It is not unusual behavior for an equals() method to return false if you hand it some other class. — azurefrog
– azurefrog, Commented Jun 15, 2015 at 18:10
Wow, I can't believe I missed that. I must be more tired than I thought. Anyways, thank you very much guys! — user2563949
– user2563949, Commented Jun 15, 2015 at 18:17

Francisco Romero · Accepted Answer · 2015-06-15 18:13:10Z

2

It is because you are not comparing 2 Strings. You have to put it like this:

Log.e("testLogic", String.valueOf(taken.getText().toString().trim().equals("1")));

because .equals() function needs two Strings. Supposing that s1 and s2 are Strings, you should do:

s1.equals(s2);

I expect it will be helpful for you!

answered Jun 15, 2015 at 18:13

Francisco Romero

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Comments

Razib · Accepted Answer · 2015-06-15 18:27:53Z

The .equals() comes from the Object class. Each class inherit it from the Object class. String class also inherited it from the Object class and override it like this -

    public boolean equals(Object anObject) {
        if (this == anObject) {
            return true;
        }
        if (anObject instanceof String) {
            String anotherString = (String)anObject;
            int n = count;
            if (n == anotherString.count) {
            char v1[] = value;
            char v2[] = anotherString.value;
            int i = offset;
            int j = anotherString.offset;
            while (n-- != 0) {
                if (v1[i++] != v2[j++])
                return false;
            }
            return true;
            }
        }
        return false;
  }

And String has not any overloaded version of equals method for char. You can see if String's .equals() method takes any object but it returns false when it is any type rather than String. It only returns true if the provided parameter is of type String and is meaningfully equals. So you have to write -

Log.e("testLogic",String.valueOf(taken.getText().toString().trim().equals("1")));

instead of -

Log.e("testLogic", String.valueOf(taken.getText().toString().trim().equals('1')));

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