Test if two objects are structurally equal?

Question

I have a company object with different departments and employees. I have successfully serialized my object and loaded it in my program again.

Now I want to test if those two objects are structurally equal. Does java offer me a tool to compare those objects?

I should add that my object has a list filled with other objects.

Or do I have to write my own test for this?

edit:

class test{

public int a

}
test t = new test();
t.a = 1;

test t1 = new test();
t1.a = 1;

now I want to compare t and t1 if they are the same based on their values.

just check if they are the instance of the same class using `isinstance` function — Aswin Murugesh, Apr 28 '13 at 18:32
Have a look at http://commons.apache.org/proper/commons-beanutils//api/org/apache/commons/beanutils/BeanComparator.html — Anders R. Bystrup, Apr 28 '13 at 18:33
Are you looking for a way to compare the contents of two `Serializable` objects for equality in their serial fields? — FThompson, Apr 28 '13 at 18:41

score 5 · Accepted Answer · edited Apr 28 '13 at 18:59

5

You can override the equals method in the Test class as follows:

public boolean equals(Object other) {
    if (other == null) {
       return false;
    }
    if (!(other instanceof Test)) {
       return false;
    }
    return this.a == ((Test) other).a;
}

Also: When overriding equals, you always should also always override the hashCode method. Please see this reference for why: Why always override hashcode() if overriding equals()?

edited Apr 28 '13 at 18:59

Hovercraft Full Of Eels

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answered Apr 28 '13 at 18:39

Rahul Bobhate

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5

Always override hashcode when overriding equals. This should be part of your answer. Your equals method signature is wrong. -1 until you correct this since what you recommend will not work and worse will mislead. Hint: the method parameter! – Hovercraft Full Of Eels Apr 28 '13 at 18:43
1

If you are using Eclipse, it can generate hashCode and equals for you. – Thierry Apr 28 '13 at 18:44
@HovercraftFullOfEels: Oops. Edited it. – Rahul Bobhate Apr 28 '13 at 18:46
You still never mentioned hashCode. Why? I've added to your answer since you didn't bother doing this. – Hovercraft Full Of Eels Apr 28 '13 at 18:51
You don't need `if (x) return true else return false`, just `return x`. This helps with readability. – arshajii Apr 28 '13 at 18:53

score 2 · Answer 2 · answered Apr 28 '13 at 18:32

2

Sounds like you can compare with overridden equals method I think...

answered Apr 28 '13 at 18:32

ChristopheCVB

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score 2 · Answer 3 · answered Apr 28 '13 at 18:33

Google Guava provides ComparisonChain:

   public int compareTo(Foo that) {
     return ComparisonChain.start()
         .compare(this.aString, that.aString)
         .compare(this.anInt, that.anInt)
         .compare(this.anEnum, that.anEnum, Ordering.natural().nullsLast())
         .result();
   }

Apache Commons provides CompareToBuilder:

   public int compareTo(Object o) {
     MyClass myClass = (MyClass) o;
     return new CompareToBuilder()
       .appendSuper(super.compareTo(o)
       .append(this.field1, myClass.field1)
       .append(this.field2, myClass.field2)
       .append(this.field3, myClass.field3)
       .toComparison();
   }
 }

Test if two objects are structurally equal?

3 Answers3

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