How to override equals method

The equals method accepts Object as the parameter. When overriding this method we need to downcast the parameter object to the specific. The downcast is not the good idea as it is not the OO. So can anyone please tell me how can we override the equals method without downcasting the parameter object. Thank you.

For comparing the objects by value overriding the equals method what I did is like this
public boolean equals(Object o){
    if( o instanceof Book){
        Book b = (Book)o;
        if(this.id == b.id)
            return true;
    return false;
}But in the above code I have to downcast the object o to the class Book. This downcasting is not a good as it is not Object-Oriented. So what I want to do is avoid the downcasting. So any idea how to do it?

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Overriding equal() method

Hi all,
I am new to this forum.This is my first post.
Please see below code...
class One
private int a,b;        //we override equal() method in this class
public One(int x,int y)
   a=x;
   b=y;
public boolean equals(Object o)
     if((o instanceof One )&&(((One)o).getAValue()==this.a)&&(((One)o).getBValue()==this.b))+
        return true;
     else
        return false;
public class ToCheckEqalityOfObjects4
public static void main(String[] args)
    One ob1=new One(2,4);
    One ob2=new One(2,4);
    One ob3=new One(6,12);
    One ob4=ob3;
    if(ob1==ob2)
      System.out.println("ob1==ob2 TRUE");
    else
      System.out.println("ob1==ob2 FALSE");
    if(ob1.equals(ob2))
      System.out.println("ob1.equals(ob2) TRUE");
    else
      System.out.println("ob1.equals(ob2) FALSE");
    if(ob4==ob3)
      System.out.println("ob4==ob3 TRUE");
    else
      System.out.println("ob4==ob3 FALSE");
    if(ob1.equals(ob3))
      System.out.println("ob4.equals(ob3) TRUE");
    else
      System.out.println("ob4.equals(ob3) FALSE");
}While compiling this code i got a error like..
E:\WINDOWS\java\IOStreams\ToCheckEqalityOfObjects4.java:23: cannot find symbol
symbol : method getAValue()
location: class IOStreams.One
     if((o instanceof One )&&(((One)o).getAValue()==this.a)&&(((One)o).getBValue()==this.b))
E:\WINDOWS\java\IOStreams\ToCheckEqalityOfObjects4.java:23: cannot find symbol
symbol : method getBValue()
location: class IOStreams.One
     if((o instanceof One )&&(((One)o).getAValue()==this.a)&&(((One)o).getBValue()==this.b))
2 errorsWhat's wrong with my code ?
Please tell me..
Thankq very much for reading this.

The error message tells you exactly what's wrong. You're calling methods that you didn't actually define.

Need help overriding equals() method

Hi I have an assignment where I have to override the equals() method, the thing that's bugging me though is my instructor says the parameter has to be Object. I understand you can pass anything through Object but if I want to get a method from the object I passed through how would I go about that? What I'm basically trying to do is compare two arrays of numbers and see if both array sizes are the same and both have the same values at each corresponding index.
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The issue here is that the signature of this equals method must match that of that which it is overriding, or in other words, it must match the equals method of Object. So it must take an object parameter. Here I would use the instanceof(...) method to see if the object matches what I want, if not, then return false, if so, cast the object as your specific object and call methods to my heart's content.

How to override a method in an inner class of the super class

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The code below is representative of my situation.
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}The method myMethod seems to be suitably overridden, but I cannot override the checkMinimum() method.
I think this is a stupid problem to do with how the ValueChecks class is instantiated. I think I need to create an instance of ValueChecks in ClassASub, and pass a reference to it into ClassA. But this will upset the way ClassA works. Could somebody enlighten me please.

vc = new ValueChecks();vc is a ValueChecks object. No matter whether you subclass ValueChecks or not, vc is always of this type, per this line of code.
// I want this to call the overridden method, but it does not, it seems to > call
// the method in this class. probably because vc belongs to this class
this.vc.checkMinimum();No, it's because again vc references a ValueChecks object, because it was created as such.
And when I say ValueChecks, I mean the original class, not the one you tried to create by the same name, attempting to override the original.

How to override ExecuteWithParms method?

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How to override toString() method ?

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int c;
Test(int size)
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AS you said, the toString method returns a String - this String is supposed to be a representation of the current instance of your class's state. In your case, your class's state is a String array, so you just pick a format for that and make a String that fits that format. Maybe you want it to spit out something like:
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hash code is computed to check the equality of two
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you can try to achieve this via separate responsibility by personalizing the form by display false on the particular control button..

Overriding hashcode method

Can u pls tell me friends why should definetly i override the hashcode method if i override equals method of the Object class

Because the contracts of equals and hashCode are strongly bound to each other.
For each objects x and y where x.equals(y) returns true x.hashCode() must be equal to y.hashCode().
If you don't follow this convention you'll get hard-to-find bugs as soon as you use your object as a key in some kind of HashMap/HashTable/...

What is hash code in Java and how it is related to equals method

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Objects in Java have hash codes associated with them. An object's hash code is a signed number that identifies the object (for example, an instance of the parent class). An object's hash code may be obtained by using the object's hashCode() method as follows:
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1. // Compare objects and then compare their hash codes
2. if (object1.equals(object2)
3. System.out.println("hash code 1 = " + object1.hashCode() +
4. ", hashcode 2 = " + object2.hashCode());
5.
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7. if (object1.hashCode() == object2.hashCode())
8. {
9. if (object1.equals(object2))
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Need help!! How to use super in equals() method and makeCopy() method?

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I don't understand how to use super in equals() method and makeCopy() method.

Try something like this ...
public boolean equals(Object other) {
if (other==null || !(other instanceof Person)) return false;
Person that = (Person) other;
return getTitle().equals(that.getTitle())
      && getName().equals(that.getName())
      && getAddress().equals(that.getAddress())
      && getTel().equals(that.getTel())
      && getEmail().equals(that.getEmail())
Notes:
* This overrides Object's public boolean equals(Object other), which is (probably) what you meant.
* You don't need to call "super.getWhatever" explicitly... just call "getWhatever" and let java workout where it's defined... this is better because if you then override getTitle() for example you don't need to change your equals method (which you would otherwise probably forget to do, which would probably have some interesting side effects.
Cheers. Keith.

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Hello everyone, I'm using ADF Faces and have the next question:
How can I override the create method which is invoked by a create form to preset an attribute in the new row (the preset value is not fixed, I have to send it to the method as a parameter as it is obtained using an EL expression)?
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Why do we need to override Hascode and Equals method?

Hi,
== checks if the two references are equal and .equlas will check if the value is same, if we want .equals to take care of both reference and value are correct. why cant I just override equals with an extra check that references are equal(==).
Please someone elaborate on this and also tell me what role hashcode plays in this.
thanks
Anirudh

anirudh1983 wrote:
if we want .equals to take care of both reference and value are correct. why cant I just override equals with an extra check that references are equal(==).Many equals() methods do run an '==' check first for efficiency (and I would recommend it if you're writing one yourself).
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How to Compare Two Strng without .equals() method

Hiii,
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Please give me the logic or code..
Your help will be appreciated

dude find the code without the equal method
public class test {
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How to override equals method

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