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Java ArrayList does not use overriden equals(Object o) method to compare


Java ArrayList does not use overriden equals(Object o) method to compare

By : calimblocky
Date : November 21 2020, 09:01 AM
wish helps you I searched for solution everywhere, but I couldn't find any mistake in my code. Why does ArrayList's contains(Object o) does not run my overridden equals(Object o) method? Consider this code: , You test
code :
list.contains(e)


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Why NullReferenceException is thrown in overriden Object.Equals method?

Why NullReferenceException is thrown in overriden Object.Equals method?


By : G. Baghini
Date : March 29 2020, 07:55 AM
I wish did fix the issue. C# does use callvirt where you get a NullReferenceException before entering the null object. But since the BCL is made for a plethora of languages they did guard against null objects in some central parts (such as string) which do use the call instruction.
Managed C++ is the most notable user of the call instruction.
Must the .equals method for objects be overriden for instances of that object type in order for them to be used as keys

Must the .equals method for objects be overriden for instances of that object type in order for them to be used as keys


By : M Sanville
Date : March 29 2020, 07:55 AM
around this issue The answer is yes.
If you are going to create instances of KeySignature on the fly, then the equals method needs to compare them "by value". The default implementation of equals simply tests to see if the objects are ==. So, you need get the hashmap to work, you need to override the default equals AND hashcode methods.
getting object from arraylist using equals method - java

getting object from arraylist using equals method - java


By : Renu Patil
Date : March 29 2020, 07:55 AM
I hope this helps you . I have a two list of objects. I want to compare both the lists. I have custom objects in these two lists. I thought i can override the equals method and get the object from the array list like - list.get(objectRef) and this should give the required object based on equals method comparison. But just came to know there is no such support yet. , You can use:
code :
list.get(list.indexOf(objectRef));
Why is the .equals() method not overriden for arrays of primitives in Java?

Why is the .equals() method not overriden for arrays of primitives in Java?


By : macchado
Date : March 29 2020, 07:55 AM
Any of those help Any Collections of arrays is mostly bad design. They should not be used together. You're probably better of by introducing a trivial, but needed class:
code :
public class Password{
     private final char[] password;

     public Password(char[] password){
         this.password = password;
     }

     @Override
     public boolean equals(Object obj){
         // equals logic
     }

     @Override
     public int hashCode(){
         // hashCode logic
     }
}
public boolean verifyUser( String username, char[] password ){
    List<Password> dbpass = getPasswords(username);
    boolean contained = dbpass.contains(new Password(password));
    overwriteWithNonsense(password);
    return contained;
}
Assumptions for .equals() method in java - compare object's instance or object's state

Assumptions for .equals() method in java - compare object's instance or object's state


By : user3020342
Date : March 29 2020, 07:55 AM
I wish did fix the issue. When I think of implementing equals for a given class I ask myself a question: what makes an object unique? What differs instance of one Person different from other? Then I use that properties for implementing equals. In your case, or in case of @Entity objects with @XtoY relationship, in my opinion there is no need to include this relationship to equals.
If for example I have a Person that has a relation to Department, the fact that a person belongs to some departments doesn't make his unique. It's his name/surname/PESEL or email and so on, and that's what I would include in equals.
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