equals again

[Praveena khandavalli]

hi all ,
here is the prog and its output is
Prints "Objects have different values";
can anybody explain why is it so...if i run the class by creating String objects rather than the MyClass object ..the result is 'equal'..i am confused please explain..thanx in advance
Praveena
--------------------------------------
1: class MyClass
2: {
3: static int maxElements;
4:
5: MyClass(int maxElements)
6: {
7: this.maxElements = maxElements;
8: }
9:
10: }
11:
12: public class Q19
13: {
14: public static void main(String[] args)
15: {
16:
17: MyClass a = new MyClass(100);
18: MyClass b = new MyClass(100);
19:
20: if(a.equals(b))
21: System.out.println("Objects have the same values");
22: else
23: System.out.println("Objects have different values");
24: }
25: }
------------------------------------------

[mark stone]

because the equals method for class String is overridden. This overridden method compares for the content in the contained string.
(this is different from the equals method for class Object)
i hope it's clear now

Originally posted by Praveena khandavalli:
hi all ,
here is the prog and its output is
Prints "Objects have different values";
can anybody explain why is it so...if i run the class by creating String objects rather than the MyClass object ..the result is 'equal'..i am confused please explain..thanx in advance
Praveena
--------------------------------------
1: class MyClass
2: {
3: static int maxElements;
4:
5: MyClass(int maxElements)
6: {
7: this.maxElements = maxElements;
8: }
9:
10: }
11:
12: public class Q19
13: {
14: public static void main(String[] args)
15: {
16:
17: MyClass a = new MyClass(100);
18: MyClass b = new MyClass(100);
19:
20: if(a.equals(b))
21: System.out.println("Objects have the same values");
22: else
23: System.out.println("Objects have different values");
24: }
25: }
------------------------------------------

[Rob Ross]

Originally posted by Praveena khandavalli:
hi all ,
here is the prog and its output is
Prints "Objects have different values";
can anybody explain why is it so...if i run the class by creating String objects rather than the MyClass object ..the result is 'equal'..i am confused please explain..thanx in advance
Praveena

MyClass extends Object (implicitly).
Object's implementation of equals() compares the two objects and returns true only if they are the same object reference. This is basically the same behavior as using the equality operator (==). Since the two objects are different objects, Object.equals() will return false. IF you want to implement an equals method that works for this example, you have to write it yourself.
In MyClass, I would add...

public boolean equals(Object obj)
{
   if (! (obj instanceof MyClass)
      return false;
   if(obj.maxElements == this.maxElements)
       return true;
   else
       return false;

}//end public boolean equals(Object obj)

Of course, in YOUR specific example, since you're using a static variable, this test for equality will ALWAYS return true. I'm not sure why you want this variable to be static.

Rob