== and .Equals() Not Working in Java

Java object equals method not work

In your case:

Right: if ( x.equals(y) )

Wrong: if ( x == y )

If the equals API is not working, then you've overridden it in your Card class, and you've implemented it wrong.

If you haven't overridden it, well then do it:

public class Card 
{
    ...
    
    @Override
    public boolean equals(final Object obj)
    {
        if (obj == this)
            return true;
            
        if (obj == null || !(obj instanceof Card)) 
            return false;
        
        Card otherCard = (Card) obj;
        
        if (otherCard.score != this.score)       return false;
        if (otherCard.symbol != this.symbol)     return false;
        if (!otherCard.warna.equals(this.warna)) return false;
        if (!otherCard.type.equals(this.type))   return false;
        if (!otherCard.value.equals(this.value)) return false;
        
        return true;
    }

}

Equals method is not working properly[solveed]

Strings and MyDate are objects, you need to compare them using equals() instead of ==.

public boolean equals(Object o) {
    boolean result = false;
    if (o instanceof Person) {
        Person other = (Person) o;
        if (this.getName().equals(other.getName())
              && this.getDob().equals(other.getDob())) {
            result = true;
        }

    }
    return result;
}

Note that this equals() implementation does not yet properly address the case in which the name or dob is null.

What is the difference between == and equals() in Java?

In general, the answer to your question is "yes", but...

• .equals(...) will only compare what it is written to compare, no more, no less.
• If a class does not override the equals method, then it defaults to the equals(Object o) method of the closest parent class that has overridden this method.
• If no parent classes have provided an override, then it defaults to the method from the ultimate parent class, Object, and so you're left with the Object#equals(Object o) method. Per the Object API this is the same as ==; that is, it returns true if and only if both variables refer to the same object, if their references are one and the same. Thus you will be testing for object equality and not functional equality.
• Always remember to override hashCode if you override equals so as not to "break the contract". As per the API, the result returned from the hashCode() method for two objects must be the same if their equals methods show that they are equivalent. The converse is not necessarily true.

not equals not working in java

For comparisons with null in Java, you use object != null

if(object != null){
  //
}

equal() Method doesn't work in Java

From this question (Why do we have to override the equals() method in Java?), you can read that the default way Java compares two objects is through their memory address. If you create two instances, both instances will have a different memory address. Hence, they are not equal. (Bottom line is that the method does work, but not as you'd expected)

That is why you have to override the equals method in your Pen class in order to 'tell' Java that if Pen.Name equals, the object itself equals.

Java Does Not Equal (!=) Not Working?

if (!"success".equals(statusCheck))

Equals method is not working for two same object

If two images having the same total size are considered equal by your equals() method (even if they don't have the same width and height), they should also have the same hashCode().

But that's not the only issue. You should also change hashCode() to ignore the file name suffixes, in order for it to fit the implementation of equals().

public int hashCode() {
    final int prime = 31;
    int result = 1;
    result = prime * result + ((filename == null) ? 0 : filename.split("\\.")[0].hashCode());
    result = prime * result + (height * width);
    return result;
}

With these two changes, the HashSet will eliminate two duplicates, resulting in:

Image: filename=smile.gif Size=20000
Image: filename=flag.jpg Size=2400
Image: filename=lenna.jpg Size=262144
Image: filename=other.jpg Size=2400
Image: filename=Lenna.jpg Size=262144

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