Common method for comparing any two Java objects

Question

I want to compare two Java objects without overriding equals method. Since I need to override equals method in n number of Classes I have, I am in need of a common utility method where we can compare two Java objects.

Something like:

A a1,a2;
B b1,b2;
C c1,c2;
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boolean isEqual1 = new ObjectComparator().isEquals(a1 , a2);
boolean isEqual2 = new ObjectComparator().isEquals(b1 , b2);
boolean isEqual3 = new ObjectComparator().isEquals(c1 , c2);

Please help me out to write a common utility for comparing any Java objects

Hope by using Field class, and getClass method we can achieve it. Please guide me.

Answer 1

Have a look at EqualsBuilder.reflectionEquals in the Apache Commons library.

From the documentation:

This method uses reflection to determine if the two Objects are equal.

It uses AccessibleObject.setAccessible to gain access to private fields. This means that it will throw a security exception if run under a security manager, if the permissions are not set up correctly. It is also not as efficient as testing explicitly.

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So, in your example it would look like:

A a1,a2;
B b1,b2;
C c1,c2;
-----
-----
boolean isEqual1 = EqualsBuilder.reflectionEquals(a1 , a2);
boolean isEqual2 = EqualsBuilder.reflectionEquals(b1 , b2);
boolean isEqual3 = EqualsBuilder.reflectionEquals(c1 , c2);

Answer 2

This may be what you are looking for EqualsBuilder.reflectionEquals

public boolean equals(Object obj) {
   return EqualsBuilder.reflectionEquals(this, obj);
}