equals method to compare two objects?

[Yuvarajsinh]

:confused:
Is it possible to compare 2 objects like we do with Strings using equals() method.
for e.g,
class A
{
int a=10,b=10,c=10;
}
class Equals
{
public static void main(String s[])
{
A a,b;
a=new A();
b=new A();
if(a.equals(b))
System.out.println("We r same...");
else
System.out.println("We r not same...");

}
}

this program gives me "We r not same....."
How does equals() work in this program?
if any one can help.....!!!

[JavaHater]

if you want to compare objects, use "==" operator

[Hibernate]

a == b
returns true if and only if a is the same instance as b.

a.equals(b)
returns true if the instances are considered equal by the "equals" method,
if you haven't written any "equals" method it will return a == b.


I suggest you add a equals method to A:

@Override //Not needed
public boolean equals(A obj)
{
    return (obj != null) && (this.a == obj.a) && (this.b == obj.b) && (this.c == obj.c)
}

[Yuvarajsinh]

thnx,
That means equals method is overridden for all inbuilt classes of Java.
and if we want the same functionality we have to override that method.
Am i right?

[demonick]

It is good practice to override the equals method for your own classes and it's a must if there will be checks for equality of instances.

[JosAH]

thnx,
That means equals method is overridden for all inbuilt classes of Java.
and if we want the same functionality we have to override that method.
Am i right?

Yep, you're right; as a rule of thumb, if you implement an equals( ... ) method you should also implement the hashCode() method so your class can be stored in a collection (think of a HashSet). Also note that if you want your objects to be 'storable' in such a collection you should be careful when you change the state (member variables) of your object that influence the result of your equals( ... ) method and/or your hashCode() method.

kind regards,

Jos